Topological Origin of Geophysical Waves [CL]

http://arxiv.org/abs/1702.07583


Symmetries and topology are central to an understanding of physics. Topology explains the precise quantization of the Hall effect and the protection of surface states in topological insulators against scattering by non-magnetic impurities or bumps. Subsequent to the discovery of the quantum spin Hall effect, states of matter with different topological properties were classified according to the discrete symmetries of the system. Recently topologically protected edge excitations have been found in artificial lattice structures that support classical waves of various types. The interplay between discrete symmetries and the topology of fluid waves has so far played no role in the study of the dynamics of oceans and atmospheres. Here we show that, as a consequence of the rotation of the Earth that breaks time reversal symmetry, equatorially trapped Kelvin and Yanai waves have a topological origin, manifesting as equatorial edge modes in the rotating shallow water model. These unidirectional edge modes are guaranteed to exist by the non-trivial global structure of the bulk Poincar\’e modes encoded through the first Chern number of value $\pm2$, in agreement with the correspondence between behavior deep in the bulk and edge excitations of a physical system. Thus the oceans and atmospheres of Earth and other rotating planets naturally share fundamental properties with topological insulators, despite the absence of an underlying lattice. As equatorially trapped Kelvin waves are an important component of El Ni\~no Southern Oscillation, and Madden-Julian Oscillation, our results demonstrate the topology plays an unexpected role in Earth’s climate system. These and other geophysical waves of topological origin are protected against static perturbations by time scale separation from other modes that inhibits scattering.

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P. Delplace, J. Marston and A. Venaille
Mon, 27 Feb 17
16/49

Comments: N/A

Dirac-Bergmann Constraints in Physics: Singular Lagrangians, Hamiltonian Constraints and the Second Noether Theorem [CL]

http://arxiv.org/abs/1702.07598


There is a review of the main mathematical properties of system described by singular Lagrangians and requiring Dirac-Bergmann theory of constraints at the Hamiltonian level. The following aspects are discussed:
i) the connection of the rank and eigenvalues of the Hessian matrix in the Euler-Lagrange equations with the chains of first and second class constraints;
ii) the connection of the Noether identities of the second Noether theorem with the Hamiltonian constraints;
iii) the Shanmugadhasan canonical transformation for the identification of the gauge variables and for the search of the Dirac observables, i.e. the quantities invariant under Hamiltonian gauge transformations.
Review paper for a chapter of a future book.

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L. Lusanna
Mon, 27 Feb 17
23/49

Comments: 38 pages

How constant shifts affect the zeros of certain rational harmonic functions [CL]

http://arxiv.org/abs/1702.07593


We study the effect of constant shifts on the zeros of rational harmomic functions $f(z) = r(z) – \conj{z}$. In particular, we characterize how shifting through the caustics of $f$ changes the number of zeros and their respective orientations. This also yields insight into the nature of the singular zeros of $f$. Our results have applications in gravitational lensing theory, where certain such functions $f$ represent gravitational point-mass lenses, and a constant shift can be interpreted as the position of the light source of the lens.

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J. Liesen and J. Zur
Mon, 27 Feb 17
25/49

Comments: 26 pages, 9 figures

Dirac-Bergmann Constraints in Relativistic Physics: Non-Inertial Frames, Point Particles, Fields and Gravity [CL]

http://arxiv.org/abs/1702.07595


There is a review of the physical theories needing Dirac-Bergmann theory of constraints at the Hamiltonian level due to the existence of gauge symmetries. It contains:
i) the treatment of systems of point particles in special relativity both in inertial and non-inertial frames with a Wigner-covariant way of eliminating relative times in relativistic bound states;
ii) the description of the electro-magnetic field in relativistic atomic physics and of Yang-Mills fields in absence of Gribov ambiguity in particle physics;
iii) the identification of the inertial gauge variables and of the physical variables in canonical ADM tetrad gravity in presence of the electro-magnetic field and of charged scalar point particles in asymptotically Minkowskian space-times without super-translations by means of a Shanmugadhasan canonical transformation to a York canonical basis adapted to ten of the 14 first-class constraints and the definition of the Hamiltonian Post-Minkowskian weak field limit.
Review paper for a chapter of a future book

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L. Lusanna
Mon, 27 Feb 17
40/49

Comments: 30 pages. arXiv admin note: substantial text overlap with arXiv:1108.3224, arXiv:1205.2481

Electron dynamics surrounding the X-line in asymmetric magnetic reconnection [CL]

http://arxiv.org/abs/1702.07244


Electron dynamics surrounding the X-line in magnetopause-type asymmetric reconnection is investigated using a two-dimensional particle-in-cell simulation. We study electron properties of three characteristic regions in the vicinity of the X-line. The fluid properties, velocity distribution functions (VDFs), and orbits are studied and cross-compared. In the low-$\beta$ side of the X-line, the normal electric field enhances the electron meandering motion from the high-$\beta$ side. The motion leads to a crescent-shaped component in the electron VDF, in agreement with recent studies. In the high-$\beta$ side of the X-line, the magnetic field line is so stretched in the third dimension that its curvature radius is comparable with typical electron Larmor radius. The electron motion becomes nonadiabatic, and therefore the electron idealness is no longer expected to hold. Around the middle of the outflow regions, the electron nonidealness is coincident with the region of the nonadiabatic motion. Finally, we introduce a finite-time mixing fraction (FTMF) to evaluate electron mixing. The FTMF marks the low-$\beta$ side of the X-line, where the nonideal energy dissipation occurs.

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S. Zenitani, H. Hasegawa and T. Nagai
Fri, 24 Feb 17
10/50

Comments: Comments are welcome

Quantum Circuit Cosmology: The Expansion of the Universe Since the First Qubit [CL]

http://arxiv.org/abs/1702.06959


We consider cosmological evolution from the perspective of quantum information. We present a quantum circuit model for the expansion of a comoving region of space, in which initially-unentangled ancilla qubits become entangled as expansion proceeds. We apply this model to the comoving region that now coincides with our Hubble volume, taking the number of entangled degrees of freedom in this region to be proportional to the de Sitter entropy. The quantum circuit model is applicable for at most 140 $e$-folds of inflationary and post-inflationary expansion: we argue that no geometric description was possible before the time $t_1$ when our comoving region was one Planck length across, and contained one pair of entangled degrees of freedom. This approach could provide a framework for modeling the initial state of inflationary perturbations.

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N. Bao, C. Cao, S. Carroll, et. al.
Fri, 24 Feb 17
11/50

Comments: 12 pages, 1 figure. Including appendix

BRS structure of Simple Model of Cosmological Constant and Cosmology [CL]

http://arxiv.org/abs/1702.07063


In arXiv:1601.02203, a simple model has been proposed in order to solve one of the problems related with the cosmological constant. The model is given by a topological field theory and the model has an infinite numbers of the BRS symmetries. The BRS symmetries are, however, spontaneously broken in general. In this paper, we investigate the BRS symmetry in more details and show that there is one and only one BRS symmetry which is not broken and the unitarity can be guaranteed. In the model, the quantum problem of the vacuum energy, which may be identified with the cosmological constant, reduces to the classical problem of the initial condition. In this paper, we investigate the cosmology given by the model and specify the region of the initial conditions which could be consistent with the evolution of the universe. We also show that there is a stable solution describing the de Sitter space-time, which may explain the accelerating expansion in the current universe.

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T. Mori, D. Nitta and S. Nojiri
Fri, 24 Feb 17
31/50

Comments: LaTeX 10 pages, 3 figures

Fifty years of cosmological particle creation [CL]

http://arxiv.org/abs/1702.07132


In the early sixties Leonard Parker discovered that the expansion of the universe can create particles out of the vacuum, opening a new and fruitfull field in physics. We give a historical review in the form of an interview that took place during the Conference ERE2014 (Valencia 1-5, September, 2014).

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L. Parker and J. Navarro-Salas
Fri, 24 Feb 17
35/50

Comments: 8 pages

The equilibrium-diffusion limit for radiation hydrodynamics [CL]

http://arxiv.org/abs/1702.07300


The equilibrium-diffusion approximation (EDA) is used to describe certain radiation-hydrodynamic (RH) environments. When this is done the RH equations reduce to a simplified set of equations. The EDA can be derived by asymptotically analyzing the full set of RH equations in the equilibrium-diffusion limit. We derive the EDA this way and show that it and the associated set of simplified equations are both first-order accurate with transport corrections occurring at second order. Having established the EDA’s first-order accuracy we then analyze the grey nonequilibrium-diffusion approximation and the grey Eddington approximation and show that they both preserve this first-order accuracy. Further, these approximations preserve the EDA’s first-order accuracy when made in either the comoving-frame (CMF) or the lab-frame (LF). While analyzing the Eddington approximation, we found that the CMF and LF radiation-source equations are equivalent when neglecting ${\cal O}(\beta^2)$ terms and compared in the LF. Of course, the radiation pressures are not equivalent. It is expected that simplified physical models and numerical discretizations of the RH equations that do not preserve this first-order accuracy will not retain the correct equilibrium-diffusion solutions. As a practical example, we show that nonequilibrium-diffusion radiative-shock solutions devolve to equilibrium-diffusion solutions when the asymptotic parameter is small.

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J. Ferguson, J. Morel and R. Lowrie
Fri, 24 Feb 17
49/50

Comments: 16 pages, 1 figure, submitted for publication to the Journal of Quantitative Spectroscopy and Radiative Transfer

Chaos Control with Ion Propulsion [CL]

http://arxiv.org/abs/1702.06581


The escape dynamics around the triangular Lagrangian point L5 in the real Sun-Earth-Moon-Spacecraft system is investigated. Appearance of the finite time chaotic behaviour suggests that widely used methods and concepts of dynamical system theory can be useful in constructing a desired mission design. Existing chaos control methods are modified in such a way that we are able to protect a test particle from escape. We introduce initial condition maps in order to have a suitable numerical method to describe the motion in high dimensional phase space. Results show that the structure of initial condition maps can be split into two well-defined domains. One of these two parts has a regular contiguous shape and is responsible for long time escape; it is a long-lived island. The other one shows a filamentary fractal structure in initial condition maps. The short time escape is governed by this object. This study focuses on a low-cost method which successfully transfers a reference trajectory between these two regions using an appropriate continuous control force. A comparison of the Earth-Moon transfer is also presented to show the efficiency of our method.

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J. Sliz, T. Kovacs and A. Suli
Thu, 23 Feb 17
20/48

Comments: 14 pages, 11 figures, accepted for publication in Astronomische Nachrichten

Positivity Bounds for Scalar Theories [CL]

http://arxiv.org/abs/1702.06134


Assuming the existence of a local, analytic, unitary UV completion in a Poincar\'{e} invariant scalar field theory with a mass gap, we derive an infinite number of positivity requirements using the known properties of the amplitude at and away from the forward scattering limit. These take the form of bounds on combinations of the pole subtracted scattering amplitude and its derivatives. In turn, these positivity requirements act as constraints on the operator coefficients in the low energy effective theory. For certain theories these constraints can be used to place an upper bound on the mass of the next lightest state that must lie beyond the low energy effective theory if such a UV completion is to ever exist.

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C. Rham, S. Melville, A. Tolley, et. al.
Thu, 23 Feb 17
38/48

Comments: 5 pages

Supernova neutrinos: fast flavor conversions near the core [CL]

http://arxiv.org/abs/1702.06836


Neutrino flux streaming from a supernova can undergo rapid flavor conversions almost immediately above the core. Focusing on this region, we study these fast conversions using a linear stability analysis. We find that, for realistic angular distributions of neutrinos, fast conversions can occur within a few nanoseconds in regions just above the neutrinosphere. Our results also show that neutrinos travelling towards the core make fast conversions more rapid. These conversions, if they exist, can have significant implications for supernova explosion mechanism and nucleosynthesis.

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M. Sen
Thu, 23 Feb 17
42/48

Comments: Presented at the XXII DAE-BRNS HEP Symposium. Proceedings to appear in European Physics Journal C

Chiral magnetic effect in the presence of electroweak interactions as a quasiclassical phenomenon [CL]

http://arxiv.org/abs/1702.06426


We provide the quasiclassical derivation of the modified chiral magnetic effect in the case when massless charged fermions moving in external electromagnetic fields interact by electroweak forces with the background matter. In our study we rely on the energy balance between the external electromagnetic field and charged particles. The obtained expression for the electric current along the external magnetic field appears to coincide with our previous results based on the purely quantum approach. We also compare our results with findings of other authors.

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M. Dvornikov and V. Semikoz
Wed, 22 Feb 17
4/37

Comments: 10 pages in LaTeX2e, 1 table

The Twist of the Draped Interstellar Magnetic Field Ahead of the Heliopause: A Magnetic Reconnection Driven Rotational Discontinuity [CL]

http://arxiv.org/abs/1702.06178


Based on the difference between the orientation of the interstellar $B_{ISM}$ and the solar magnetic fields, there was an expectation that the magnetic field direction would rotate dramatically across the heliopause (HP). However, the Voyager 1 spacecraft measured very little rotation across the HP. Previously we showed that the $B_{ISM}$ twists as it approaches the HP and acquires a strong T component (East-West). Here we establish that reconnection in the eastern flank of the heliosphere is responsible for the twist. On the eastern flank the solar magnetic field has twisted into the positive N direction and reconnects with the Southward pointing component of the $B_{ISM}$. Reconnection drives a rotational discontinuity (RD) that twists the $B_{ISM}$ into the -T direction and propagates upstream in the interstellar medium towards the nose. The consequence is that the N component of $B_{ISM}$ is reduced in a finite width band upstream of the HP. Voyager 1 currently measures angles ($\delta=sin^{-1}(B_{N}/B)$) close to solar values. We present MHD simulations to support this scenario, suppressing reconnection in the nose region while allowing it in the flanks, consistent with recent ideas about reconnection suppression from diamagnetic drifts. The jump in plasma $\beta$ (the plasma to magnetic pressure) across the nose of HP is much greater than in the flanks because the heliosheath $\beta$ is greater there than in the flanks. Large-scale reconnection is therefore suppressed in the nose but not at the flanks. Simulation data suggest that $B_{ISM}$ will return to its pristine value $10-15~AU$ past the HP.

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M. Opher, J. Drake, M. Swisdak, et. al.
Wed, 22 Feb 17
13/37

Comments: 19 pages, 5 figures, submitted

Search for right-handed neutrinos from dark matter annihilation with gamma-rays [CL]

http://arxiv.org/abs/1702.06145


Several extensions of the Standard Model contain right-handed (sterile) neutrinos in the GeV-TeV mass range. Due to their mixing with the active neutrinos, they may give rise to novel effects in cosmology, neutrino physics, and collider searches. In addition, right-handed neutrinos can also appear as final states from dark matter annihilations, with important implications for dark matter indirect detection searches. In this paper, we use current data from the Fermi Large Area Telescope (6-year observation of dwarf spheroidal galaxies) and H.E.S.S. (10-year observation of the Galactic center) to constrain the annihilation of dark matter into right-handed neutrinos. We consider right-handed neutrino with masses between 10 GeV and 1 TeV, including both two-body and three-body decays, to derive bounds on the dark matter annihilation rate, $\langle \sigma v\rangle$, as a function of the dark matter mass. Our results show, in particular, that the thermal dark matter annihilation cross section, $3\times 10^{-26}\, {\rm cm^3 s^{-1}} $, into right-handed neutrinos is excluded for dark matter masses smaller than $200$ GeV.

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M. Campos, F. Queiroz, C. Yaguna, et. al.
Wed, 22 Feb 17
15/37

Comments: 19 pages, 7 figures

Getting Super-Excited with Modified Dispersion Relations [CL]

http://arxiv.org/abs/1702.06101


We demonstrate that in some regions of parameter space, modified dispersion relations can lead to highly populated excited states, which we dub as “super-excited” states. In order to prepare such super-excited states, we invoke dispersion relations that have negative slope in an interim sub-horizon phase at high momenta. This behaviour of quantum fluctuations can lead to large corrections relative to the Bunch-Davies power spectrum, which mimics highly excited initial conditions. We identify the Bogolyubov coefficients that can yield these power spectra. In the course of this computation, we also point out the shortcomings of the gluing method for evaluating the power spectrum and the Bogolyubov coefficients. As we discuss, there are other regions of parameter space, where the power spectrum does not get modified. Therefore, modified dispersion relations can also lead to so-called “calm excited states” as well. We conclude by commenting on the possibility of obtaining these modified dispersion relations within the Effective Field Theory of Inflation.

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A. Ashoorioon, R. Casadio, G. Geshnizjani, et. al.
Wed, 22 Feb 17
23/37

Comments: 1+19 pages, 4 figures

Gravitational wave, collider and dark matter signals from a scalar singlet electroweak baryogenesis [CL]

http://arxiv.org/abs/1702.06124


We analyse a simple extension of the SM with just an additional scalar singlet coupled to the Higgs boson. We discuss the possible probes for electroweak baryogenesis in this model including collider searches, gravitational wave and direct dark matter detection signals. We show that a large portion of the model parameter space exists where the observation of gravitational waves would allow detection while the indirect collider searches would not.

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A. Beniwal, M. Lewicki, J. Wells, et. al.
Wed, 22 Feb 17
30/37

Comments: 24 pages, 7 figures

Generalized $α$-attractor models from geometrically finite hyperbolic surfaces [CL]

http://arxiv.org/abs/1702.06484


We consider four-dimensional gravity coupled to a non-linear sigma model whose scalar manifold is a geometrically finite hyperbolic surface $\Sigma$, which may be non-compact and may have finite or infinite area. When the space-time is an FLRW universe, such theories produce a very wide generalization of two-field $\alpha$-attractor models, being parameterized by a positive constant $\alpha$, by the choice of a finitely-generated surface group $\Gamma\subset \mathrm{PSL}(2,\mathbb{R})$ (which is isomorphic with the fundamental group of $\Sigma$) and by the choice of a scalar potential defined on $\Sigma$. The traditional $\alpha$-attractor models arise when $\Gamma$ is the trivial group, in which case $\Sigma$ is the Poincar\'{e} disk. When $\Sigma$ is non-compact, we show that our generalized models have the same universal behavior as ordinary $\alpha$-attractors if inflation happens near any of the Freudenthal ends of $\Sigma$, for trajectories which are well approximated by non-canonically parameterized geodesics near the ends. We also discuss some aspects of these models in the SRST approximation and give a general prescription for their study through uniformization in the non-elementary case. Our generalized models can sustain multipath inflation starting near any of the ends of $\Sigma$ and proceeding toward the compact core. They illustrate interesting consequences of nonlinear sigma models whose scalar manifold is not simply connected and provide a large class of tractable cosmological models with non-trivial topology of the scalar field space.

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C. Lazaroiu and C. Shahbazi
Wed, 22 Feb 17
35/37

Comments: 53 pages

Cosmic Ray RF detection with the ASTRONEU array [CL]

http://arxiv.org/abs/1702.05794


Results will be shown from the ASTRONEU array developed and operated in the outskirts of Patras, Greece. An array of 9 scintillator detectors and 3 antennas were deployed to study Extensive Air Showers (EAS) as a tool for calibrating an underwater neutrino telescope, possible other applications in muon tomography, education purposes, and last but not least, the detection of air showers via their electromagnetic signature. This is the first stage of a total of 24 scintillator counters and 6 RF antennas to complete the array. In this work, results with regard to the electromagnetic detection of showers will be shown. The method of operation and analysis will be presented. The purpose of this project was to demonstrate the adequacy of the method to detect cosmic events even in the presence of high urban electromagnetic background, using noise filters, timing, signal polarization, and eventual comparison with well understood event reconstruction using the scintillator detectors. The results indicate that cosmic showers were detected and the method can be used for the complete array.

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I. Manthos, I. Gkialas, G. Bourlis, et. al.
Tue, 21 Feb 17
1/70

Comments: 18 pages, 11 figures

On the dark radiation problem in the axiverse [CL]

http://arxiv.org/abs/1702.05924


String scenarios generically predict that we live in a so called axiverse: the Universe with about a hundred of light axion species which are decoupled from the Standard Model particles. However, the axions can couple to the inflaton which leads to their production after inflation. Then, these axions remain in the expanding Universe contributing to the dark radiation component, which is severely bounded from present cosmological data. We place a general constraint on the axion production rate and apply it to several variants of reasonable inflaton-to-axion couplings. The limit merely constrains the number of ultralight axions and the relative strength of inflaton-to-axion coupling. It is valid in both large and small field inflationary models irrespectively of the axion energy scales and masses. Thus, the limit is complementary to those associated with the Universe overclosure and axion isocurvature fluctuations. In particular, a hundred of axions is forbidden if inflaton universally couples to all the fields at reheating. In the case of gravitational sector being responsible for the reheating of the Universe (which is a natural option in all inflationary models with modified gravity), the axion production can be efficient. We find that in the Starobinsky $R^2$-inflation even a single axion (e.g. the standard QCD-axion) is in tension with the Planck data, making the model inconsistent with the axiverse. The general conclusion is that an inflation with inefficient reheating mechanism and low reheating temperature may be in tension with the presence of light scalars.

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D. Gorbunov and A. Tokareva
Tue, 21 Feb 17
7/70

Comments: N/A

How Anomalous Resistivity Accelerates Magnetic Reconnection [CL]

http://arxiv.org/abs/1702.06109


Whether Turbulence-induced anomalous resistivity (AR) can facilitate a fast magnetic reconnection in collisionless plasma is a subject of active debate for decades. A particularly difficult problem in experimental and numerical simulation studies of the problem is how to distinguish the effects of AR from those originating from Hall-effect and other non-turbulent processes in the generalized Ohm’s. In this paper, using particle-in-cell simulations, we present a case study of how AR produced by Buneman Instability accelerates magnetic reconnection. We first show that in a thin current layer, the AR produced by Buneman instability spontaneously breaks the magnetic field lines and causes impulsive fast non-Hall magnetic line annihilation on electron-scales with a rate reaching 0.6~$V_A$. However, the electron-scale magnetic line annihilation is not a necessary condition for the dissipation of magnetic energy, but rather a result of the inhomogeneity of the AR. On the other hand, the inhomogeneous drag arising from a Buneman instability driven by the intense electron beams at the x-line in a 3D magnetic reconnection can drive in the electron diffusion region electron-scale magnetic line annihilation. The electron-scale annihilations play an essential role in accelerating the magnetic reconnection with a rate two times faster than the non-turbulent Hall-dominated 2D magnetic reconnection. The reconnection rate is enhanced around the x-line, and the coupling between the AR carried out by the reconnection outflow and the Hall effect leads to the breaking of the symmetric structure of the ion diffusion region and the enhancement of the outward Poynting flux.

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H. Che
Tue, 21 Feb 17
12/70

Comments: submitted to Physics of Plasma

ENDOR study of nitrogen hyperfine and quadrupole tensors in vanadyl porphyrins of heavy crude oil [CL]

http://arxiv.org/abs/1702.06066


We report the observation of pulsed electron-nuclear double resonance (ENDOR) spectrum caused by interactions of the nitrogen nuclei 14N with the unpaired electron of the paramagnetic vanadyl complexes VO2+ of vanadyl porphyrins in natural crude oil. We provide detailed experimental and theoretical characterization of the nitrogen hyperfine and quadrupole tensors.

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I. Gracheva, M. Gafurov, G. Mamin, et. al.
Tue, 21 Feb 17
29/70

Comments: 6 pages, 2 Figures

Hot magnetized nuclear matter: Thermodynamic and Saturation Properties [CL]

http://arxiv.org/abs/1702.04765


We have used a realistic nuclear potential, AV18, and a many body technique, the lowest order constraint variational (LOCV) approach, to calculate the properties of hot magnetized nuclear matter. By investigating the free energy, spin polarization parameter, and symmetry energy, we have studied the temperature and magnetic field dependence of the saturation properties of magnetized nuclear matter. In addition, we have calculated the equation of state of magnetized nuclear matter at different temperatures and magnetic fields. It was found that the flashing temperature of nuclear matter decreases by increasing the magnetic field. In addition, we have studied the effect of the magnetic field on liquid gas phase transition of nuclear matter. The liquid gas coexistence curves, the order parameter of the liquid gas phase transition, and the properties of critical point at different magnetic fields have been calculated.

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Z. Rezaei and G. Bordbar
Tue, 21 Feb 17
30/70

Comments: 30 pages, 13 figures, 2 tables. Accepted for publication in European Physical Journal A

The evolution of gravitons in accelerating cosmologies: the case of extended gravity [CL]

http://arxiv.org/abs/1702.05517


We discuss the production and evolution of cosmological gravitons showing how the cosmological background affects their dynamics. Besides, the detection of cosmological gravitons could constitute an extremely important signature to discriminate among different cosmological models. Here we consider the cases of scalar-tensor gravity and $f(R)$ gravity where it is demonstrated the amplification of graviton amplitude changes if compared with General Relativity. Possible observational constraints are discussed.

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S. Capozziello, M. Laurentis, S. Nojiri, et. al.
Tue, 21 Feb 17
32/70

Comments: 14 pages

Highly magnetized neutron stars in a many-body forces formalism [CL]

http://arxiv.org/abs/1702.05685


In this work, we study the effects of different magnetic field configurations in neutron stars described by a many-body forces formalism (MBF model). The MBF model is a relativistic mean field formalism that takes into account many-body forces by means of a meson field dependence of the nuclear interaction coupling constants. We choose the best parametrization of the model that reproduces nuclear matter properties at saturation and also describes massive neutron stars. We assume matter to be in beta-equilibrium, charge neutral and at zero temperature. Magnetic fields are taken into account both in the equation of state and in the structure of the stars by the self-consistent solution of the Einstein-Maxwell equations. We assume a poloidal magnetic field distribution and calculate its effects on neutron stars, showing its influence on the gravitational mass and deformation of the stars.

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R. Gomes, B. Franzon, V. Dexheimer, et. al.
Tue, 21 Feb 17
34/70

Comments: Contribution to the Proceedings of the VII International Workshop on Astronomy and Relativistic Astrophysics – IWARA 2016

Generic Phase Portrait Analysis of the Finite-time Singularities and Generalized Teleparallel Gravity [CL]

http://arxiv.org/abs/1702.05786


We analyze the finite-time singularity types using a generic framework of the phase portrait geometric approach. This technique requires that the Friedmann system to be written as a one dimensional autonomous system. We exhibit a scale factor that can realize the four singularity types, then we show a detailed discussion for each case. Moreover, we show how different singularity types can play essential roles in different cosmological scenarios. Among several modified gravity theories, we show that the $f(T)$ cosmology is in comfort with the phase portrait analysis. Therefore, we reconstruct the $f(T)$ theory which generates these phase portraits. We also perform a complementary analysis using the effective equation of state. Furthermore, we investigate the role of the torsion fluid in realizing the cosmic singularities.

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W. Hanafy and G. Nashed
Tue, 21 Feb 17
37/70

Comments: revtex4 LaTeX2e: 26 pages, 2 Tables and 10 Figures

The population of highly magnetized neutron stars [CL]

http://arxiv.org/abs/1702.05684


In this work, we study the effects of strong magnetic field configurations on the population of neutron stars. The stellar matter is described within a relativistic mean field formalism which considers many-body force contributions in the scalar couplings. We choose the parametrization of the model that reproduces nuclear matter properties at saturation and also describes massive hyperon stars. Hadronic matter is modeled at zero temperature, in beta-equilibrium, charge neutral and populated by the baryonic octet, electrons and muons. Magnetic effects are taken into account in the structure of stars by the solution of the Einstein-Maxwell equations with the assumption of a poloidal magnetic field distribution. Our results show that magnetic neutron stars are populated essencialy by nucleons and leptons, due to the fact that strong magnetic fields decrease the central density of stars and, hence, supress the appearance of exotic particles.

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R. Gomes, V. Dexheimer, B. Franzon, et. al.
Tue, 21 Feb 17
40/70

Comments: Prepared for Conference “Compact Stars in the QCD phase diagram V” 23-27 May 2016 GSSI and LNGS (L’Aquila, Italy)

Understanding the importance of transient resonances in extreme mass ratio inspirals [CL]

http://arxiv.org/abs/1702.05481


Extreme mass ratio inspirals (EMRIs) occur when a compact object orbits a much larger one, like a solar-mass black hole around a supermassive black hole. The orbit has 3 frequencies which evolve through the inspiral. If the orbital radial frequency and polar frequency become commensurate, the system passes through a transient resonance. Evolving through resonance causes a jump in the evolution of the orbital parameters. We study these jumps and their impact on EMRI gravitational-wave detection. Jumps are smaller for lower eccentricity orbits; since most EMRIs have small eccentricities when passing through resonances, we expect that the impact on detection will be small. Neglecting the effects of transient resonances leads to a loss of ~4% of detectable signals for an astrophysically motivated population of EMRIs.

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C. Berry, R. Cole, P. Canizares, et. al.
Tue, 21 Feb 17
52/70

Comments: 2 pages, 0 figures; to appear in the proceedings of the 11th International LISA Symposium

Constraints on the production of primordial magnetic seeds in pre-big bang cosmology [CL]

http://arxiv.org/abs/1702.06030


We study the amplification of the electromagnetic fluctuations, and the production of “seeds” for the cosmic magnetic fields, in a class of string cosmology models whose scalar and tensor perturbations reproduce current observations and satisfy known phenomenological constraints. We find that the condition of efficient seeds production can be satisfied and compatible with all constraints only in a restricted region of parameter space, but we show that such a region has significant intersections with the portions of parameter space where the produced background of relic gravitational waves is strong enough to be detectable by aLIGO/Virgo and/or by eLISA.

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M. Gasperini
Tue, 21 Feb 17
60/70

Comments: 20 pages, 3 figures

Invariant Measure of the One Loop Quantum Gravitational Back-Reaction on Inflation [CL]

http://arxiv.org/abs/1702.05694


We use dimensional regularization in pure quantum gravity on de Sitter background to evaluate the one loop expectation value of an invariant operator which gives the local expansion rate. We show that the renormalization of this nonlocal composite operator can be accomplished using the counterterms of a simple local theory of gravity plus matter, at least at one loop order. This renormalization completely absorbs the one loop correction, which accords with the prediction that the lowest secular back-reaction should be a 2-loop effect.

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S. Miao, N. Tsamis and R. Woodard
Tue, 21 Feb 17
66/70

Comments: 26 pages, 2 figures, 1 table, uses LaTeX2e

Experimental overview on Future Solar and Heliospheric research [CL]

http://arxiv.org/abs/1702.05091


Solar and heliospheric cosmic rays provide a unique perspective in cosmic ray research: we can observe not only the particles, but also the properties of the plasmas in which the they are accelerated and propagate, using in situ and high-resolution remote sensing instruments. The heliospheric cosmic ray observations typically require space missions, which face stern competition against planetary and astrophysics missions, and it can take up to decades from the initial concept proposal until the actual observing of the cosmic rays can commence. Therefore it is important to have continuity in the cosmic ray mission timeline. In this overview, we review the current status and the future outlook in the experimental solar and heliospheric research. We find that the current status of the available cosmic ray observations is good, but that many of the spacecraft are near the end of their feasible mission life. We describe the three missions currently being prepared for launch, and discuss the future outlook of the solar and heliospheric cosmic ray missions.

Read this paper on arXiv…

T. Laitinen
Mon, 20 Feb 17
9/37

Comments: XXV ECRS 2016 Proceedings – eConf C16-09-04.3

Nuclear equation of state for core-collapse supernova simulations with realistic nuclear forces [CL]

http://arxiv.org/abs/1702.05324


A new table of the nuclear equation of state (EOS) based on realistic nuclear potentials is constructed for core-collapse supernova numerical simulations. Adopting the EOS of uniform nuclear matter constructed by two of the present authors with the cluster variational method starting from the Argonne v18 and Urbana IX nuclear potentials, the Thomas-Fermi calculation is performed to obtain the minimized free energy of a Wigner-Seitz cell in non-uniform nuclear matter. As a preparation for the Thomas-Fermi calculation, the EOS of uniform nuclear matter is modified so as to remove the effects of deuteron cluster formation in uniform matter at low densities. Mixing of alpha particles is also taken into account following the procedure used by Shen et al. (1998, 2011). The critical densities with respect to the phase transition from non-uniform to uniform phase with the present EOS are slightly higher than those with the Shen EOS at small proton fractions. The critical temperature with respect to the liquid-gas phase transition decreases with the proton fraction in a more gradual manner than in the Shen EOS. Furthermore, the mass and proton numbers of nuclides appearing in non-uniform nuclear matter with small proton fractions are larger than those of the Shen EOS. These results are consequences of the fact that the density derivative coefficient of the symmetry energy of our EOS is smaller than that of the Shen EOS.

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H. Togashi, K. Nakazato, Y. Takehara, et. al.
Mon, 20 Feb 17
16/37

Comments: 40 pages, 15 figures, accepted for publication in Nuclear Physics A. The EOS table constructed in this study is available on the Web at this http URL

Ab initio calculations of the isotopic dependence of nuclear clustering [CL]

http://arxiv.org/abs/1702.05177


Nuclear clustering describes the appearance of structures resembling smaller nuclei such as alpha particles (4He nuclei) within the interior of a larger nucleus. While clustering is important for several well-known examples, little is known about the general nature of clustering in nuclei. In this letter we present lattice Monte Carlo calculations based on chiral effective field theory for the ground states of helium, beryllium, carbon, and oxygen isotopes. By computing model-independent measures that probe three- and four-nucleon correlations at short distances, we determine the effective number of alpha clusters in any nucleus as well as their shape compared to alpha particles in vacuum. We also introduce a new computational approach called the pinhole algorithm, which solves a long-standing deficiency of auxiliary-field Monte Carlo simulations in computing density correlations relative to the center of mass. We use the pinhole algorithm to determine the proton and neutron density distributions and the geometry of cluster correlations in 12C, 14C, and 16C. The structural similarities among the carbon isotopes suggest that 14C and 16C have excitations analogous to the well-known Hoyle state resonance in 12C.

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S. Elhatisari, E. Epelbaum, H. Krebs, et. al.
Mon, 20 Feb 17
17/37

Comments: 5 + 9 pages (main + supplemental materials), 4 + 6 figures (main + supplemental materials)

Two-Higgs-Doublet-Portal Dark-Matter Models in Light of Direct Search and LHC Data [CL]

http://arxiv.org/abs/1702.02924


We explore simple Higgs-portal models of dark matter (DM) with spin 1/2, 3/2, and 1, respectively, applying to them constraints from the LUX and PandaX-II direct detection experiments and from LHC measurements on the 125-GeV Higgs boson. With only one Higgs doublet, we find that the spin-1/2 DM having a purely scalar coupling to the Higgs doublet is viable only in a narrow range of mass near the Higgs pole, whereas the vector DM is still allowed if its mass is also close to the Higgs pole or exceeds 1.4 TeV, both in line with earlier analyses. Moreover, the spin-3/2 DM is in a roughly similar situation to the spin-1/2 DM, but has even more restricted surviving parameter space. We also consider the two-Higgs-doublet extension of each of the preceding models, assuming that the expanded Yukawa sector is that of the two-Higgs-doublet model of type II. We show that in these two-Higgs-doublet-portal models significant portions of the DM mass regions excluded in the simplest scenarios by the direct search bounds can be recovered due to suppression of the DM effective interactions with nucleons at some ratios of the $CP$-even Higgs bosons’ couplings to the up and down quarks. Some parts of the regained parameter space can yield a DM-nucleon scattering cross-section that is far less than its current experimental limit or even goes below the neutrino-background floor.

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C. Chang, X. He and J. Tandean
Fri, 17 Feb 17
13/43

Comments: 24 pages, 10 figures. arXiv admin note: text overlap with arXiv:1609.03551

New constraints and discovery potential of sub-GeV dark matter with xenon detectors [CL]

http://arxiv.org/abs/1702.04730


Existing xenon dark matter (DM) direct detection experiments can probe the DM-nucleon interaction of DM with a sub-GeV mass through a search for bremsstrahlung from the recoiling xenon atom. We show that LUX’s constraints on sub-GeV DM, which utilise the scintillation (S1) and ionisation (S2) signals, are approximately three orders of magnitude more stringent than previous xenon constraints in this mass range, derived from the XENON10 and XENON100 S2-only searches. The new LUX constraints provide the most stringent direct detection constraints for DM particles with a mass below 0.5 GeV. In addition, the bremsstrahlung signal in LUX and its successor LZ maintain the discrimination between background and signal events so that an unambiguous discovery of sub-GeV DM is possible. We show that LZ has the potential to reconstruct the DM mass with 20% accuracy for particles lighter than 0.5 GeV.

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C. McCabe
Fri, 17 Feb 17
20/43

Comments: 6 pages, 3 figures

Robotic Telescopes in Education [CL]

http://arxiv.org/abs/1702.04835


The power of robotic telescopes to transform science education has been voiced by multiple sources, since the 1980s. Since then, much technical progress has been made in robotic telescope provision to end users via a variety of different approaches. The educational transformation hoped for by the provision of this technology has, so far, yet to be achieved on a scale matching the technical advancements. In this paper, the history, definition, role and rationale of optical robotic telescopes with a focus on their use in education is provided. The current telescope access providers and educational projects and their broad uses in traditional schooling, undergraduate and outreach are then outlined. From this background, the current challenges to the field, which are numerous, are then presented. This review is concluded with a series of recommendations for current and future projects that are apparent and have emerged from the literature.

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E. Gomez and M. Fitzgerald
Fri, 17 Feb 17
21/43

Comments: 42 pages, 16 figures, 2 tables

Electron train backgrounds in liquid xenon dark matter search detectors are indeed due to thermalization and trapping [CL]

http://arxiv.org/abs/1702.04805


Electron emission from liquid into gaseous xenon is a cornerstone of dark matter search detectors such as ZEPLIN, XENON, LUX and LZ. The probability of emission is a function of the applied electric field E, and electrons which fail to pass from the liquid into the gas have been previously hypothesized to become thermalized and trapped. This article shows, for the first time, quantitative agreement between an electron emission model and existing data. The model predicts that electrons in the liquid must surmount a typical potential barrier phi_b=0.34+-0.01 eV in order to escape into the gas. This value is a factor of about x2 smaller than has previously been calculated or inferred. Knowledge of phi_b allows calculation of the lifetime of thermalized, trapped electrons. The value is O(10) ms, which appears to be compatible with XENON10 observations of electron train backgrounds. As these backgrounds limit the sensitivity of dark sector dark matter searches, possible mitigations are discussed.

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P. Sorensen
Fri, 17 Feb 17
26/43

Comments: N/A

SHARP: A Spatially Higher-order, Relativistic Particle-in-Cell Code [CL]

http://arxiv.org/abs/1702.04732


Numerical heating in particle-in-cell (PIC) codes currently precludes the accurate simulation of cold, relativistic plasma over long periods, severely limiting their applications in astrophysical environments. We present a spatially higher order accurate relativistic PIC algorithm in one spatial dimension which conserves charge and momentum exactly. We utilize the smoothness implied by the usage of higher order interpolation functions to achieve a spatially higher order accurate algorithm (up to 5th order). We validate our algorithm against several test problems — thermal stability of stationary plasma, stability of linear plasma waves, and two-stream instability in the relativistic and non-relativistic regimes. Comparing our simulations to exact solutions of the dispersion relations, we demonstrate that SHARP can quantitatively reproduce important kinetic features of the linear regime. Our simulations have a superior ability to control energy non-conservation and avoid numerical heating in comparison to common second order schemes. We provide a natural definition for convergence of a general PIC algorithm: the complement of physical modes captured by the simulation, i.e., lie above the Poisson noise, must grow commensurately with the resolution. This implies that it is necessary to simultaneously increase the number of particles per cell and decrease the cell size. We demonstrate that traditional ways for testing for convergence fail, leading to plateauing of the energy error. This new PIC code enables to faithfully study the long-term evolution of plasma problems that require absolute control of the energy and momentum conservation.

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M. Shalaby, A. Broderick, P. Chang, et. al.
Fri, 17 Feb 17
28/43

Comments: 25 pages, 18 figures, submitted to ApJ

On the waveforms of gravitationally lensed gravitational waves [CL]

http://arxiv.org/abs/1702.04724


Strong lensing by intervening galaxies can produce multiple images of gravitational waves from sources at cosmological distances. These images acquire additional phase-shifts as the over-focused wavefront passes through itself along the line of sight. Time domain waveforms of Type-II images (associated with saddle points of the time delay) exhibit a non-trivial distortion from the unlensed waveforms. This phenomenon is in addition to the usual frequency-independent magnification, and happens even in the geometric limit where the wavelength is much shorter than the deflector’s gravitational length scale. Similarly, Type-III images preserve the original waveform’s shape but exhibit a sign flip. We show that for non-precessing binaries undergoing circular inspiral and merger, these distortions are equivalent to rotating the line of sight about the normal to the orbital plane by $45^\circ$ (Type II) and $90^\circ$ (Type III). This effect will enable us to distinguish between the different topological types among a set of multiple images, and give us valuable insight into the lens model. Furthermore, we show that for eccentric binaries, the waveform of a Type-II image is distorted in a manner that is inequivalent to a change of the source’s orbital parameters.

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L. Dai and T. Venumadhav
Fri, 17 Feb 17
31/43

Comments: 5 pages, 4 figures, comments welcome

Constraints on a generalized deceleration parameter from cosmic chronometers and its thermodynamic implications [CL]

http://arxiv.org/abs/1702.04916


In this paper, we have proposed a generalized parametrization for the deceleration parameter $q$ in order to study the evolutionary history of the universe. We have shown that the proposed model can reproduce three well known $q$-parametrized models for some specific values of the model parameter $\alpha$. We have used the latest compilation of the Hubble parameter measurements obtained from the cosmic chronometer (CC) method (in combination with the local value of the Hubble constant $H_{0}$) and the Type Ia supernova (SNIa) data to place constraints on the parameters of the model for different values of $\alpha$. We have found that the resulting constraints on the deceleration parameter and the dark energy equation of state support the $\Lambda$CDM model within $1\sigma$ confidence level at the present epoch. Finally, we have given a thermodynamic motivation for such a parametrization by showing that our model is well consistent with the generalized second law of thermodynamics as well as thermodynamic equilibrium.

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A. Mamon and S. Saha
Fri, 17 Feb 17
34/43

Comments: 10 pages, 6 figures

Gravitational wave sources: reflections and echoes [CL]

http://arxiv.org/abs/1702.04833


The recent detection of gravitational waves has generated interest in alternatives to the black hole interpretation of sources. One set of such alternatives involves a prediction of gravitational wave “echoes”. We consider two aspects of possible echoes: First, general features of echoes coming from spacetime reflecting conditions. We find that the detailed nature of such echoes does not bear any clear relationship to quasi-normal frequencies. Second, we point out the pitfalls in the analysis of local reflecting “walls” near the horizon of rapidly rotating black holes.

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R. Price and G. Khanna
Fri, 17 Feb 17
38/43

Comments: 8 pages, 5 figures

Non-Invertibility of spectral x-ray photon counting data with pileup [CL]

http://arxiv.org/abs/1702.04993


-In the Alvarez-Macovski method [R.E. Alvarez and A. Macovski, Phys. Med. Biol., 1976, 733-744], the attenuation coefficient is approximated as a linear combination of functions of energy multiplied by coefficients that depend on the material composition at points within the object. The method then computes the line integrals of the basis set coefficient from measurements with different x-ray spectra. This paper shows that the transformation from photon counting detector data with pileup to the line integrals can become ill-conditioned under some circumstances leading to highly increased noise. Methods: An idealized model that includes pileup and quantum noise is used. The noise variance of the line integral estimates is computed using the Cram{\`e}r-Rao lower bound (CRLB). The CRLB is computed as a function of object thickness for photon counting detector data with three and four bin pulse height analysis (PHA) and low and high pileup. Results: With four bin PHA data the transformation is well conditioned with either high or low pileup. With three bin PHA and high pileup, the transformation becomes ill-conditioned for specific values of object attenuation. At these values the CRLB variance increases by approximately 10 5 compared with the four bin PHA or low pileup results. The condition number of the forward transformation matrix also shows a spike at those attenuation values. Conclusion: Designers of systems using counting detectors should study the stability of the line integral estimator output with their data.

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R. Alvarez
Fri, 17 Feb 17
42/43

Comments: arXiv admin note: text overlap with arXiv:1702.01006

Factorized Runge-Kutta-Chebyshev Methods [CL]

http://arxiv.org/abs/1702.03818


The second-order extended stability Factorized Runge-Kutta-Chebyshev (FRKC2) class of explicit schemes for the integration of large systems of PDEs with diffusive terms is presented. FRKC2 schemes are straightforward to implement through ordered sequences of forward Euler steps with complex stepsizes, and easily parallelised for large scale problems on distributed architectures.
Preserving 7 digits for accuracy at 16 digit precision, the schemes are theoretically capable of maintaining internal stability at acceleration factors in excess of 6000 with respect to standard explicit Runge-Kutta methods. The stability domains have approximately the same extents as those of RKC schemes, and are a third longer than those of RKL2 schemes. Extension of FRKC methods to fourth-order, by both complex splitting and Butcher composition techniques, is discussed.
A publicly available implementation of the FRKC2 class of schemes may be obtained from maths.dit.ie/frkc

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S. OSullivan
Thu, 16 Feb 17
11/45

Comments: 9 pages, 6 figures, accepted to the proceedings of Astronum 2016 – 11th Annual International Conference on Numerical Modeling of Space Plasma Flows, June 6-10, 2016

Completion of the universal I-Love-Q relations in compact stars including the mass [CL]

http://arxiv.org/abs/1702.04568


In a recent paper we applied a rigorous perturbed matching framework to show the amendment of the mass of rotating stars in Hartle’s model. Here, we apply this framework to the tidal problem in binary systems. Our approach fully accounts for the correction to the Love numbers needed to obtain the universal $I$-Love-$Q$ relations. We compute the corrected mass vs radius configurations of rotating quark stars, revisiting a classical paper on the subject. These corrections allow us to find a universal relation involving the second-order contribution to the mass $\delta M$. We thus complete the set of universal relations for the tidal problem in binary systems, involving four perturbation parameters, namely $I$, Love, $Q$, and $\delta M$. These relations can be used to obtain the perturbation parameters directly from observational data.

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B. Reina, N. Sanchis-Gual, R. Vera, et. al.
Thu, 16 Feb 17
20/45

Comments: 6 pages, 2 figures. Sent for publication to MNRAS

Extending bimetric models of massive gravity to avoid to rely on the Vainshtein mechanism on local scales and the Higuchi bound on cosmological scales [CL]

http://arxiv.org/abs/1702.04490


This article extends bimetric formulations of massive gravity to make the mass of the graviton to depend on its environment. This minimal extension offers a novel way to reconcile massive gravity with local tests of general relativity without invoking the Vainshtein mechanism. On cosmological scales, it is argued that the model is stable and that it circumvents the Higuchi bound, hence relaxing the constraints on the parameter space. This extension is very generic and robust and a simple specific example is described.

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A. Felice, S. Mukohyama and J. Uzan
Thu, 16 Feb 17
28/45

Comments: 5 pages, uses RevTeX4.1

Sterile neutrino dark matter from right-handed neutrino oscillations [CL]

http://arxiv.org/abs/1702.04526


We propose a scenario where sterile neutrino (either warm or cold) dark matter (DM) is produced through (non-resonant) oscillations among right-handed neutrinos (RHNs) and can constitute the whole DM in the Universe. We study this production mechanism in a simple setup with three RHNs, where the lightest RHN can be sterile neutrino DM whose mixing with left-handed neutrinos is sufficiently small while heavier RHNs can have non-negligible mixings with left-handed neutrinos to explain the neutrino masses by the seesaw mechanism. We also demonstrate that, in our scenario, the production of sterile RHN DM from the decay of a heavier RHN is subdominant compared with the RHN oscillation production due to the X-ray and small scale structure constraints.

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K. Kadota and K. Kaneta
Thu, 16 Feb 17
37/45

Comments: 6 pages, 2 figures

The cosmological CP odd axion field as the coherent Berry's phase of the Universe [CL]

http://arxiv.org/abs/1702.04354


We study a testable dark matter (DM) model outside of the standard WIMP paradigm. The model is unique in a sense that the observed ratio $\Omega_{\rm dark} \simeq \Omega_{\rm visible}$ for visible and dark matter densities finds its natural explanation as a result of their common QCD origin when both types of matter (DM and visible) are formed during the QCD transition and both are proportional to single dimensional parameter of the system, $\Lambda_{\rm QCD}$. The focus of the present work is the detail study of the dynamics of the $\cal{CP}$-odd coherent axion field $a(x)$ just before the QCD transition. We argue that the baryon charge separation effect on the largest possible scales inevitably occurs as a result of merely existence of the coherent axion field in early Universe. It leads to preferential formation of one species of nuggets on the scales of the visible Universe where the axion field $a(x)$ is coherent. A natural outcome of this preferential evolution is that only one type of the visible baryons (not anti- baryons) remains in the system after the nuggets complete their formation. This represents a specific mechanism on how the baryon charge separation mechanism (when the Universe is neutral, but visible part of matter consists the baryons and not anti-baryons) replaces the conventional “baryogenesis” proposals.
The rare events of annihilation of the anti-nuggets with visible matter lead to a number of observable effects, which are consistent with all known astrophysical, cosmological, satellite and ground based constraints. Furthermore, there is a number of frequency bands where some excess of emission was observed, and this model may explain some portion, or even entire excess of the observed radiation in these frequency bands. We also comment on implications of these studies for the axion search experiments.

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S. Ge, X. Liang and A. Zhitnitsky
Thu, 16 Feb 17
40/45

Comments: 23 pages, 4 figures

Time-domain metric reconstruction for self-force applications [CL]

http://arxiv.org/abs/1702.04204


We present a new method for calculation of the gravitational self-force (GSF) in Kerr geometry, based on a time-domain reconstruction of the metric perturbation from curvature scalars. In this approach, the GSF is computed directly from a certain scalar-like self-potential that satisfies the time-domain Teukolsky equation on the Kerr background. The approach is computationally much cheaper than existing time-domain methods, which rely on a direct integration of the linearised Einstein’s equations and are impaired by mode instabilities. At the same time, it retains the utility and flexibility of a time-domain treatment, allowing calculations for any type of orbits (including highly eccentric or unbound ones) and the possibility of self-consistently evolving the orbit under the effect of the GSF. Here we formulate our method, and present a first numerical application, for circular geodesic orbits in Schwarzschild geometry. We discuss further applications.

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L. Barack and P. Giudice
Wed, 15 Feb 17
5/47

Comments: 21 pages, 7 figures

Electroweak monopoles and the electroweak phase transition [CL]

http://arxiv.org/abs/1702.04068


We consider an isolated electroweak monopole solution within the Standard Model with a non-linear Born-Infeld extension of the hypercharge gauge field. Monopole (and dyon) solutions in such an extension are regular and their masses are predicted to be proportional to the Born-Infeld mass parameter. We argue that cosmological production of electroweak monopoles may delay the electroweak phase transition and make it more strongly first order for monopole masses $M\gtrsim 9.3\cdot 10^3$ TeV, while the nucleosynthesis constraints on the abundance of relic monopoles impose the bound $M\lesssim 2.3\cdot 10^4$ TeV. The monopoles with a mass in this shallow range may be responsible for the dynamical generation of the matter-antimatter asymmetry during the electroweak phase transition.

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S. Arunasalam and A. Kobakhidze
Wed, 15 Feb 17
10/47

Comments: 11 pages, 1 figure

Centennial evolution of monthly solar wind speeds: Fastest monthly solar wind speeds from long-duration coronal holes [CL]

http://arxiv.org/abs/1702.03924


High speed solar wind streams (HSSs) are very efficient drivers of geomagnetic activity at high latitudes. In this paper we use a recently developed $\Delta{H}$ parameter of geomagnetic activity, calculated from the night-side hourly magnetic field measurements of the Sodankyl\”a observatory, as a proxy for solar wind (SW) speed at monthly time resolution in 1914-2014 (solar cycles 15-24). The seasonal variation in the relation between monthly $\Delta{H}$ and solar wind speed is taken into account by calculating separate regressions between $\Delta{H}$ and SW speed for each month. Thereby, we obtain a homogeneous series of proxy values for monthly solar wind speed for the last 100 years. We find that the strongest HSS-active months of each solar cycle occur in the declining phase, in years 1919, 1930, 1941, 1952, 1959, 1973, 1982, 1994 and 2003. Practically all these years are the same or adjacent to the years of annual maximum solar wind speeds. This implies that the most persistent coronal holes, lasting for several solar rotations and leading to the highest annual SW speeds, are also the sources of the highest monthly SW speeds. Accordingly, during the last 100 years, there were no coronal holes of short duration (of about one solar rotation) that would produce faster monthly (or solar rotation) averaged solar wind than the most long-living coronal holes in each solar cycle produce.

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R. Lukianova, L. Holappa and K. Mursula
Wed, 15 Feb 17
16/47

Comments: N/A