# Charged massive scalar field configurations supported by a spherically symmetric charged reflecting shell [CL]

The physical properties of bound-state charged massive scalar field configurations linearly coupled to a spherically symmetric charged reflecting shell are studied {\it analytically}. To that end, we solve the Klein-Gordon wave equation for a static scalar field of proper mass $\mu$, charge coupling constant $q$, and spherical harmonic index $l$ in the background of a charged shell of radius $R$ and electric charge $Q$. It is proved that the dimensionless inequality $\mu R<\sqrt{(qQ)^2-(l+1/2)^2}$ provides an upper bound on the regime of existence of the composed charged-spherical-shell-charged-massive-scalar-field configurations. Interestingly, we explicitly show that the {\it discrete} spectrum of shell radii $\{R_n(\mu,qQ,l)\}_{n=0}^{n=\infty}$ which can support the static bound-state charged massive scalar field configurations can be determined analytically. We confirm our analytical results by numerical computations.

S. Hod
Fri, 17 Mar 17
11/50

# Recommendations of the LHC Dark Matter Working Group: Comparing LHC searches for heavy mediators of dark matter production in visible and invisible decay channels [CL]

Weakly-coupled TeV-scale particles may mediate the interactions between normal matter and dark matter. If so, the LHC would produce dark matter through these mediators, leading to the familiar ‘mono-X’ search signatures, but the mediators would also produce signals without missing momentum via the same vertices involved in their production. This document from the LHC Dark Matter Working Group suggests how to compare searches for these two types of signals in case of vector and axial-vector mediators, based on a workshop that took place on September 19/20, 2016 and subsequent discussions. These suggestions include how to extend the spin-1 mediated simplified models already in widespread use to include lepton couplings. This document also provides analytic calculations of the relic density in the simplified models and reports an issue that arose when ATLAS and CMS first began to use preliminary numerical calculations of the dark matter relic density in these models.

A. Albert, M. Backovic, A. Boveia, et. al.
Fri, 17 Mar 17
16/50

# Lectures on the Infrared Structure of Gravity and Gauge Theory [CL]

This is a redacted transcript of a course given by the author at Harvard in spring semester 2016. It contains a pedagogical overview of recent developments connecting the subjects of soft theorems, the memory effect and asymptotic symmetries in four-dimensional QED, nonabelian gauge theory and gravity with applications to black holes. The lectures may be viewed online at https://goo.gl/3DJdOr. Please send typos or corrections to strominger@physics.harvard.edu.

A. Strominger
Fri, 17 Mar 17
18/50

# Pulsar Timing Constraints on Physics Beyond the Standard Model [CL]

We argue that massive quantum fields source low-frequency long-wavelength metric fluctuations through the quantum fluctuations of their stress-energy, given reasonable assumptions about the analytic structure of its correlators. This can be traced back to the non-local nature of the gauge symmetry in General Relativity, which prevents an efficient screening of UV scales (what we call the cosmological non-constant problem). We define a covariant and gauge-invariant observable which probes line-of-sight spacetime curvature fluctuations on an observer’s past lightcone, and show that current pulsar timing data constrains any massive particle to $m\lesssim 600$ GeV. This astrophysical bound severely limits the possibilities for physics beyond the standard model below the scale of quantum gravity.

N. Afshordi, H. Kim and E. Nelson
Fri, 17 Mar 17
20/50

# Directional Sensitivity In Light-Mass Dark Matter Searches With Single-Electron Resolution Ionization Detectors [CL]

We present a method for using solid state detectors with directional sensitivity to dark matter interactions to detect low-mass Weakly Interacting Massive Particles (WIMPs) originating from galactic sources. In spite of a large body of literature for high-mass WIMP detectors with directional sensitivity, there is no available technique to cover WIMPs in the mass range <1 GeV. We argue that single-electron resolution semiconductor detectors allow for directional sensitivity once properly calibrated. We examine commonly used semiconductor material response to these low-mass WIMP interactions.

F. Kadribasic, N. Mirabolfathi, K. Nordlund, et. al.
Fri, 17 Mar 17
32/50

# Secluded and Flipped Dark Matter and Stueckelberg Extensions of the Standard Model [CL]

We consider here three dark matter models with the gauge symmetry of the standard model plus an additional local $U(1)_D$ factor. One model is secluded and two models are flipped. All of these models include one dark fermion and one vector boson that attains mass through the Stueckelberg mechanism. We show that the flipped models provide examples dark matter composed of “least interacting particles” (LIPs). Such particles are therefore compatible with the constraints obtained from both laboratory measurements and astrophysical observations.

E. Fortes, V. Pleitez and F. Stecker
Fri, 17 Mar 17
37/50

# Study of statistical properties of hybrid statistic in coherent multi-detector compact binary coalescences Search [CL]

In this article, we revisit the problem of coherent multi-detector search of gravitational wave from compact binary coalescence with Neutron stars and Black Holes using advanced interferometers like LIGO-Virgo. Based on the loss of optimal multi-detector signal-to-noise ratio (SNR), we construct a hybrid statistic as a best of maximum-likelihood-ratio(MLR) statistic tuned for face-on and face-off binaries. The statistical properties of the hybrid statistic is studied. The performance of this hybrid statistic is compared with that of the coherent MLR statistic for generic inclination angles. Owing to the single synthetic data stream, the hybrid statistic gives low false alarms compared to the multi-detector MLR statistic and small fractional loss in the optimum SNR for a large range of binary inclinations. We have demonstrated that for a LIGO-Virgo network and binary inclination, \epsilon < 70 deg. and \epsilon > 110 deg., the hybrid statistic captures more than 98% of network optimum matched filter SNR with low false alarm rate. The Monte-Carlo exercise with two distributions of incoming inclination angles namely, U[cos(\epsilon)] and more realistic distribution proposed by B. F. Schutz are performed with hybrid statistic and gave ~5% and ~7% higher detection probability respectively compared to the two stream multi-detector MLR statistic for a fixed false alarm probability of 10^-5.

K. Haris and A. Pai
Fri, 17 Mar 17
42/50

Comments: Published in Phys. Rev. D

# Clustering of Gamma-Ray bursts through kernel principal component analysis [CL]

We consider the problem related to clustering of gamma-ray bursts (from “BATSE” catalogue) through kernel principal component analysis in which our proposed kernel outperforms results of other competent kernels in terms of clustering accuracy and we obtain three physically interpretable groups of gamma-ray bursts. The effectivity of the suggested kernel in combination with kernel principal component analysis in revealing natural clusters in noisy and nonlinear data while reducing the dimension of the data is also explored in two simulated data sets.

Fri, 17 Mar 17
43/50

# When the Universe Expands Too Fast: Relentless Dark Matter [CL]

We consider a modification to the standard cosmological history consisting of introducing a new species $\phi$ whose energy density red-shifts with the scale factor $a$ like $\rho_\phi \propto a^{-(4+n)}$. For $n>0$, such a red-shift is faster than radiation, hence the new species dominates the energy budget of the universe at early times while it is completely negligible at late times. If equality with the radiation energy density is achieved at low enough temperatures, dark matter can be produced as a thermal relic during the new cosmological phase. Dark matter freeze-out then occurs at higher temperatures compared to the standard case, implying that reproducing the observed abundance requires significantly larger annihilation rates. Here, we point out a completely new phenomenon, which we refer to as $\textit{relentless}$ dark matter: for large enough $n$, unlike the standard case where annihilation ends shortly after the departure from thermal equilibrium, dark matter particles keep annihilating long after leaving chemical equilibrium, with a significant depletion of the final relic abundance. Relentless annihilation occurs for $n \geq 2$ and $n \geq 4$ for s-wave and p-wave annihilation, respectively, and it thus occurs in well motivated scenarios such as a quintessence with a kination phase. We discuss a few microscopic realizations for the new cosmological component and highlight the phenomenological consequences of our calculations for dark matter searches.

F. DEramo, N. Fernandez and S. Profumo
Thu, 16 Mar 17
15/92

# The Novel ABALONE Photosensor Technology [CL]

The patented and proven ABALONE Photosensor Technology (Daniel Ferenc, U.S. Patent 9,064,678, 2010) has the capability of opening new horizons in the fields of fundamental physics, functional medical imaging, and nuclear security. This article discusses our new technology and overviews the unprecedented performance of ABALONE Photosensors, produced in the custom designed production line at UC Davis and continuously tested since 2013. In conclusion, the modern ABALONE Technology is far superior to prior art in performance, robustness and the capacity for integration into large area detector shells. It is about two orders of magnitude more cost effective while being mass-producible with a relatively low investment.

D. Ferenc, A. Chang and M. Ferenc
Thu, 16 Mar 17
44/92

Comments: 16 pages, 7 figures, Submitted for publication to Nuclear Instruments And Methods In Physics Research A on March 12, 2017 (Ms. Ref. No.: NIMA-D-17-00243)

# Early Universe Higgs dynamics in the presence of the Higgs-inflaton and non-minimal Higgs-gravity couplings [CL]

Apparent metastability of the electroweak vacuum poses a number of cosmological questions. These concern evolution of the Higgs field to the current vacuum, and its stability during and after inflation. Higgs-inflaton and non-minimal Higgs-gravity interactions can make a crucial impact on these considerations potentially solving the problems. In this work, we allow for these couplings to be present simultaneously and study their interplay. We find that different combinations of the Higgs-inflaton and non-minimal Higgs-gravity couplings induce effective Higgs mass during and after inflation. This crucially affects the Higgs stability considerations during preheating. In particular, a wide range of the couplings leading to stable solutions becomes allowed.

Y. Ema, M. Karciauskas, O. Lebedev, et. al.
Thu, 16 Mar 17
47/92

# Baryogenesis at a Lepton-Number-Breaking Phase Transition [CL]

We study a scenario in which the baryon asymmetry of the universe arises from a cosmological phase transition where lepton-number is spontaneously broken. If the phase transition is first order, a lepton-number asymmetry can arise at the bubble wall, through dynamics similar to electroweak baryogenesis, but involving right-handed neutrinos. In addition to the usual neutrinoless double beta decay in nuclear experiments, the model may be probed through a variety of “baryogenesis by-products,” which include a stochastic background of gravitational waves created by the colliding bubbles. Depending on the model, other aspects may include a network of topological defects that produce their own gravitational waves, additional contribution to dark radiation, and a light pseudo-Goldstone boson (majoron) as dark matter candidate.

A. Long, A. Tesi and L. Wang
Thu, 16 Mar 17
63/92

Comments: 21 pages + 10 appendices & references, 3 figures

# General dynamical properties of cosmological models with nonminimal kinetic coupling [CL]

We consider cosmological dynamics in the theory of gravity with the scalar field possessing the nonminimal kinetic coupling to curvature given as $\eta G^{\mu\nu}\phi_{,\mu}\phi_{,\nu}$, where $\eta$ is an arbitrary coupling parameter, and the scalar potential $V(\phi)$ which assumed to be as general as possible. With an appropriate dimensionless parameterization we represent the field equations as an autonomous dynamical system which contains ultimately only one arbitrary function $\chi (x)= 8 \pi G |\eta| V(x/\sqrt{8 \pi G})$. Then, assuming the rather general properties of $\chi(x)$, we analyze stationary points and their stability, as well as all possible asymptotical regimes of the dynamical system. It has been shown that for a broad class of $\chi(x)$ there exist attractors representing three accelerated regimes of the Universe evolution, including de Sitter expansion (or late-time inflation), the Little Rip scenario, and the Big Rip scenario. As the specific examples, we consider a power-law potential $V(\phi)=M^4(\phi/\phi_0)^\alpha$, Higgs-like potential $V(\phi)=\frac{\lambda}{4}(\phi^2-\phi_0^2)^2$, and exponential potential $V(\phi)=M^4 e^{-\phi/\phi_0}$.

J. Matsumoto and S. Sushkov
Thu, 16 Mar 17
65/92

Comments: 26 pages, 3 figures, 3 tables

# Non-cyclic geometric phases and helicity transitions for neutrino oscillations in magnetic field [CL]

We show that neutrino spin and spin-flavor transitions involve non-vanishing geometric phases. Analytical expressions are derived for non-cyclic geometric phases arising due to neutrino oscillations in magnetic fields and matter. Several calculations are performed for different cases of rotating and non-rotating magnetic fields in the context of solar neutrinos and neutrinos produced inside neutron stars. It is shown that the neutrino eigenstates carry non-vanishing geometric phases even at large distances from their original point of production. Also the effects of critical magnetic fields and cross boundary effects in case of neutrinos emanating out of neutron stars are analyzed.

S. Joshi and S. Jain
Thu, 16 Mar 17
87/92

# Constructing Gravitational Waves from Generic Spin-Precessing Compact Binary Inspirals [CL]

The coalescence of compact objects is one of the most promising sources of gravitational waves for ground-based interferometric detectors, such as advanced LIGO and Virgo. Generically, com- pact objects in binaries are expected to be spinning with spin angular momenta misaligned with the orbital angular momentum, causing the orbital plane to precess. This precession adds rich structure to the gravitational waves, introducing such complexity that an analytic closed-form description has been unavailable until now. We here construct the first closed-form frequency- domain gravitational waveforms that are valid for generic spin-precessing quasicircular compact binary inspirals. We first construct time-domain gravitational waves by solving the post-Newtonian precession equations of motion with radiation reaction through multiple scale analysis. We then Fourier transform these time-domain waveforms with the method of shifted uniform asymptotics to obtain closed-form expressions for frequency-domain waveforms. We study the accuracy of these analytic, frequency-domain waveforms relative to waveforms obtained by numerically evolving the post-Newtonian equations of motion and find that they are suitable for unbiased parameter estimation for 99.2%(94.6%) of the binary configurations we studied at a signal-to-noise ratio of 10(25). These new frequency-domain waveforms could be used for detection and parameter estimation studies due to their accuracy and low computational cost.

K. Chatziioannou, A. Klein, N. Yunes, et. al.
Tue, 14 Mar 17
8/74

Comments: 21 pages, submitted to Phys. Rev. D

# Global constraints on absolute neutrino masses and their ordering [CL]

Within the standard three-neutrino framework, the absolute neutrino masses and their ordering (either normal, NO, or inverted, IO) are currently unknown. However, the combination of current data coming from oscillation experiments, neutrinoless double beta decay searches, and cosmological surveys, can provide interesting constraints for such unknowns in the sub-eV mass range, down to O(0.1) eV in some cases. We discuss current limits on absolute neutrino mass observables by performing a global data analysis, that includes the latest results from oscillation experiments, neutrinoless double beta decay bounds from the KamLAND-Zen experiment, and constraints from representative combinations of Planck measurements and other cosmological data sets. In general, NO appears to be somewhat favored with respect to IO at the level of ~2 sigma, mainly by neutrino oscillation data (especially atmospheric), corroborated by cosmological data in some cases. Detailed constraints are obtained via the chi^2 method, by expanding the parameter space either around separate minima in NO and IO, or around the absolute minimum in any ordering. Implications for upcoming oscillation and non-oscillation neutrino experiments, including beta-decay searches, are also discussed.

F. Capozzi, E. Valentino, E. Lisi, et. al.
Tue, 14 Mar 17
14/74

Comments: 17 pages, including 3 tables and 11 figures

# Isotope shift and search for metastable superheavy elements in astrophysical data [CL]

Spectral lines belonging to the short-lifetime heavy radioactive elements up to Es ($Z$=99) have been found in the spectra of the Przybylski’s star. We suggest that these unstable elements may be decay products of a “magic” metastable nucleus belonging to the the island of stability where the nuclei have a magic number of neutrons $N=184$. The laboratory-produced nuclei have a significantly smaller number of neutrons. To identify spectra of the $N=184$ isotopes of these nuclei and their neutron-reach superheavy decay products in astrophysical data we calculate the isotope shift which should be added to the laboratory – measured wavelenghs. The results for the isotopic shifts in the strongest optical electromagnetic transitions in No, Lr, Nh, Fl,and $Z$=120 elements are presented.

V. Dzuba, V. Flambaum and J. Webb
Tue, 14 Mar 17
16/74

# Cosmological Implications of Nonlocal Gravity [CL]

We present extensions of the treatment contained in our recent paper on nonlocal Newtonian cosmology [C. Chicone and B. Mashhoon, J. Math. Phys. 57, 072501 (2016)]. That is, the implications of the recent nonlocal generalization of Einstein’s theory of gravitation are further investigated within the regime of Newtonian cosmology. In particular, we treat the nonlocal problem of structure formation for a spherically symmetric expanding dust model and show numerically that as the central density contrast grows, it tends to decrease slowly with radial distance as the universe expands. The nonlocal violation of Newton’s shell theorem provides a physical interpretation of our numerical results.

C. Chicone and B. Mashhoon
Tue, 14 Mar 17

Comments: 51 pages, 6 figures. Dedicated to Friedrich W. Hehl in honor of his 80th birthday

# Classical collapse to black holes and white hole quantum bounces: A review [CL]

In the last four decades different programs have been carried out aiming at understanding the final fate of gravitational collapse of massive bodies once some prescriptions for the behaviour of gravity in the strong field regime are provided. The general picture arising from most of these scenarios is that the classical singularity at the end of collapse is replaced by a bounce. The most striking consequence of the bounce is that the black hole horizon may live for only a finite time. The possible implications for astrophysics are important since, if these models capture the essence of the collapse of a massive star, an observable signature of quantum gravity may be hiding in astrophysical phenomena. One intriguing idea that is implied by these models is the possible existence of exotic compact objects, of high density and finite size, that may not be covered by an horizon. The present article outlines the main features of these collapse models and some of the most relevant open problems. The aim is to provide a comprehensive (as much as possible) overview of the current status of the field from the point of view of astrophysics. As a little extra, a new toy model for collapse leading to the formation of a quasi static compact object is presented.

D. Malafarina
Tue, 14 Mar 17
25/74

# Synthetic streams in a Gravitational Wave inspiral search with a multi-detector network [CL]

Gravitational Wave Inspiral search with a global network of interferometers when carried in a phase coherent fashion would mimic an effective multi-detector network with synthetic streams constructed by the linear combination of the data from different detectors. For the first time, we demonstrate that the two synthetic data streams pertaining to the two polarizations of Gravitational Wave can be derived prior to the maximum-likelihood analysis in a most natural way using the technique of singular-value-decomposition applied to the network signal-to-noise ratio vector. We construct the network matched filters in combined network plus spectral space which capture both the synthetic streams. We further show that the network LLR is then sum of the LLR of each synthetic stream. The four extrinsic parameters are mapped to the two amplitudes and two phases. The maximization over these is a straightforward approach closely linked to the single detector approach. Towards the end, we connect all the previous works related to the multi-detector Gravitational Wave inspiral search and express in the same notation in order to bring under the same footing.

K. Haris and A. Pai
Tue, 14 Mar 17
26/74

Comments: LIGO laboratory document number: LIGO-P1300229

# The Gibbs paradox, the Landauer principle and the irreversibility associated with tilted observers [CL]

It is well known that, in the context of General Relativity, some spacetimes, when described by a congruence of comoving observers, may consist in a distribution of a perfect (non-dissipative) fluid, whereas the same spacetime as seen by a “tilted”‘ (Lorentz-boosted) congruence of observers, may exhibit the presence of dissipative processes. As we shall see, the appearence of entropy producing processes are related to the tight dependence of entropy on the specific congruence of observers. This fact is well illustrated by the Gibbs paradox. The appearance of such dissipative processes, as required by the Landauer principle, are necessary, in order to erase the different amount of information stored by comoving observers, with respect to tilted ones.

L. Herrera
Tue, 14 Mar 17
28/74

Comments: 10 pages Latex. Invited contribution for the special issue “Advances in Relativistic Statistical Mechanics” published in Entropy

# Performance comparison of multi-detector detection statistics in targeted compact binary coalescence GW search [CL]

Global network of advanced Interferometric gravitational wave (GW) detectors are expected to be on-line soon. Coherent observation of GW from a distant compact binary coalescence (CBC) with a network of interferometers located in different continents give crucial information about the source such as source location and polarization information. In this paper we compare different multi-detector network detection statistics for CBC search. In maximum likelihood ratio (MLR) based detection approaches, the likelihood ratio is optimized to obtain the best model parameters and the best likelihood ratio value is used as statistic to make decision on the presence of signal. However, an alternative Bayesian approach involves marginalization of the likelihood ratio over the parameters to obtain the average likelihood ratio. We obtain an analytical expression for the Bayesian statistic using the two effective synthetic data streams for targeted search of non-spinning compact binary systems with an uninformative prior on the parameters. Simulations are carried out for testing the validity of the approximation and comparing the detection performance with the maximum likelihood ratio based statistics. We observe that the MLR {\it hybrid} statistic gives comparable or better performance with respect to the Bayesian statistic.

K. Haris and A. Pai
Tue, 14 Mar 17
60/74

# The Early Scientific Contributions of J. Robert Oppenheimer: Why Did the Scientific Community Miss the Black Hole Opportunity? [CL]

We aim to carry out an assessment of the scientific value of Oppenheimer’s research on black holes in order to determine and weigh possible factors to explain its neglect by the scientific community, and even by Oppenheimer himself. Dealing primarily with the science and looking closely at the scientific culture and the scientific conceptual belief system of the 1930s, the present article seeks to supplement the existent literature on the subject by enriching the explanations and possibly complicating the guiding questions. We suggest a rereading of Oppenheimer as a more intriguing, ahead-of-his-time figure.

M. Ortega-Rodriguez, H. Solis-Sanchez, E. Boza-Oviedo, et. al.
Tue, 14 Mar 17
63/74

Comments: 19 pages, Phys. Perspect. (2017)

# An improved algorithm for narrow-band searches of continuous gravitational waves [CL]

Continuous gravitational waves signals, emitted by asymmetric spinning neutron stars, are among the main targets of current detectors like Advanced LIGO and Virgo. In the case of sources, like pulsars, which rotational parameters are measured through electromagnetic observations, typical searches assume that the gravitational wave frequency is at a given known fixed ratio with respect to the star rotational frequency. For instance, for a neutron star rotating around one of its principal axis of inertia the gravitational signal frequency would be exactly two times the rotational frequency of the star. It is possible, however, that this assumption is wrong. This is why search algorithms able to take into account a possible small mismatch between the gravitational waves frequency and the frequency inferred from electromagnetic observations have been developed. In this paper we present an improved pipeline to perform such narrow-band searches for continuous gravitational waves from neutron stars, about three orders of magnitude faster than previous implementations. The algorithm that we have developed is based on the {\it 5-vectors} framework and is able to perform a fully coherent search over a frequency band of width $\mathcal{O}$(Hertz) and for hundreds of spin-down values running a few hours on a standard workstation. This new algorithm opens the possibility of long coherence time searches for objects which rotational parameters are highly uncertain.

S. Mastrogiovanni, P. Astone, S. DAntonio, et. al.
Mon, 13 Mar 17
5/48

Comments: 19 pages, 8 figures, 6 tables, submitted to CQG

# The RIT binary black hole simulations catalog [CL]

The RIT numerical relativity group is releasing a public catalog of black-hole-binary waveforms. The initial release of the catalog consists of 126 recent simulations that include precessing and non precessing systems with mass ratios $q=m_1/m_2$ in the range $1/6\leq q\leq1$. The catalog contains information about the initial data of the simulation, the waveforms extrapolated to infinity, as well as information about the peak luminosity and final remnant black hole properties. These waveforms can be used to independently interpret gravitational wave signals from laser interferometric detectors and

J. Healy, C. Lousto, Y. Zlochower, et. al.
Mon, 13 Mar 17
7/48

# Influence of a large-scale field on energy dissipation in magnetohydrodynamic turbulence [CL]

In magnetohydrodynamic (MHD) turbulence, the large-scale magnetic field sets a preferred local direction for the small-scale dynamics, altering the statistics of turbulence from the isotropic case. This happens even in the absence of a total magnetic flux, since MHD turbulence forms randomly oriented large-scale domains of strong magnetic field. It is therefore customary to study small-scale magnetic plasma turbulence by assuming a strong background magnetic field relative to the turbulent fluctuations. This is done, for example, in reduced models of plasmas, such as reduced MHD, reduced-dimension kinetic models, gyrokinetics, etc., which make theoretical calculations easier and numerical computations cheaper. Recently, however, it has become clear that the turbulent energy dissipation is concentrated in the regions of strong magnetic field variations. A significant fraction of the energy dissipation may be localized in very small volumes corresponding to the boundaries between strongly magnetized domains. In these regions the reduced models are not applicable. This has important implications for studies of particle heating and acceleration in magnetic plasma turbulence. The goal of this work is to systematically investigate the relationship between local magnetic field variations and magnetic energy dissipation, and to understand its implications for modeling energy dissipation in realistic turbulent plasmas.

V. Zhdankin, S. Boldyrev and J. Mason
Mon, 13 Mar 17
8/48

Comments: 6 pages, 5 figures, to appear in Monthly Notices of the Royal Astronomical Society

# Effective Description of Higher-Order Scalar-Tensor Theories [CL]

Most existing theories of dark energy and/or modified gravity, involving a scalar degree of freedom, can be conveniently described within the framework of the Effective Theory of Dark Energy, based on the unitary gauge where the scalar field is uniform. We extend this effective approach by allowing the Lagrangian in unitary gauge to depend on the time derivative of the lapse function. Although this dependence generically signals the presence of an extra scalar degree of freedom, theories that contain only one propagating scalar degree of freedom, in addition to the usual tensor modes, can be constructed by requiring the initial Lagrangian to be degenerate. Starting from a general quadratic action, we derive the dispersion relations for the linear perturbations around Minkowski and a cosmological background. Our analysis directly applies to the recently introduced Degenerate Higher-Order Scalar-Tensor (DHOST) theories. For these theories, we find that one cannot recover a Poisson-like equation in the static linear regime except for the subclass that includes the Horndeski and so-called “beyond Horndeski” theories. We also discuss Lorentz-breaking models inspired by Horava gravity.

D. Langlois, M. Mancarella, K. Noui, et. al.
Mon, 13 Mar 17
12/48

# Does a Nash theory of gravity make dark energy superfluous? [CL]

Recently Aadne and Gr{\o}n have argued that dark energy may follow naturally from a Nash theory of gravity. In this brief note I argue why this cannot be the case.

K. Lake
Mon, 13 Mar 17
35/48

# Description of the evolution of inhomogeneities on a Dark Matter halo with the Vlasov equation [CL]

We use a direct numerical integration of the Vlasov equation in spherical symmetry with a background gravitational potential to determine the evolution of a collection of particles in different models of a galactic halo. Such a collection is assumed to represent a dark matter inhomogeneity which reaches a stationary state determined by the virialization of the system. We describe some features of the stationary states and, by using several halo models, obtain distinctive signatures for the evolution of the inhomogeneities in each of the models.

P. Dominguez-Fernandez, E. Jimenez-Vazquez, M. Alcubierre, et. al.
Mon, 13 Mar 17
36/48

Comments: 26 pages, 67 figures, 1 table, submitted to MNRAS

# Exotic Compact Objects and How to Quench their Ergoregion Instability [CL]

Gravitational-wave astronomy can give us access to the structure of black holes, potentially probing microscopic or even Planckian corrections at the horizon scale, as those predicted by some quantum-gravity models of exotic compact objects. A generic feature of these models is the replacement of the horizon by a reflective surface. Objects with these properties are prone to the so-called ergoregion instability when they spin sufficiently fast. We investigate in detail a simple model consisting of scalar perturbations of a Kerr geometry with a reflective surface near the horizon. The instability depends on the spin, on the compactness, and on the reflectivity at the surface. The instability time scale increases logarithmically in the black-hole limit but, for a perfectly reflecting object, this is not enough to prevent the instability from occurring on dynamical time scales. However, we find that an absorption rate at the surface as small as 0.4% (reflectivity coefficient as large as $|{\cal R}|^2=0.996$) is sufficient to quench the instability completely. Our results suggest that exotic compact objects are not necessarily ruled out by the ergoregion instability.

E. Maggio, P. Pani and V. Ferrari
Mon, 13 Mar 17
37/48

# How Well Do We Know The Supernova Equation of State? [CL]

We give an overview about equations of state (EOS) which are currently available for simulations of core-collapse supernovae and neutron star mergers. A few selected important aspects of the EOS, such as the symmetry energy, the maximum mass of neutron stars, and cluster formation, are confronted with constraints from experiments and astrophysical observations. There are just very few models which are compatible even with this very restricted set of constraints. These remaining models illustrate the uncertainty of the uniform nuclear matter EOS at high densities. In addition, at finite temperatures the medium modifications of nuclear clusters represent a conceptual challenge. In conclusion, there has been significant development in the recent years, but there is still need for further improved general purpose EOS tables.

M. Hempel, M. Oertel, S. Typel, et. al.
Mon, 13 Mar 17
38/48

Comments: 6 pages, 1 table, 1 figure; proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)

# Cross section measurement of the astrophysically important 17O(p,gamma)18F reaction in a wide energy range [CL]

The 17O(p,g)18F reaction plays an important role in hydrogen burning processes in different stages of stellar evolution. The rate of this reaction must therefore be known with high accuracy in order to provide the necessary input for astrophysical models.
The cross section of 17O(p,g)18F is characterized by a complicated resonance structure at low energies. Experimental data, however, is scarce in a wide energy range which increases the uncertainty of the low energy extrapolations. The purpose of the present work is therefore to provide consistent and precise cross section values in a wide energy range.
The cross section is measured using the activation method which provides directly the total cross section. With this technique some typical systematic uncertainties encountered in in-beam gamma-spectroscopy experiments can be avoided.
The cross section was measured between 500 keV and 1.8 MeV proton energies with a total uncertainty of typically 10%. The results are compared with earlier measurements and it is found that the gross features of the 17O(p,g)18F excitation function is relatively well reproduced by the present data. Deviation of roughly a factor of 1.5 is found in the case of the total cross section when compared with the only one high energy dataset. At the lowest measured energy our result is in agreement with two recent datasets within one standard deviation and deviates by roughly two standard deviations from a third one. An R-matrix analysis of the present and previous data strengthen the reliability of the extrapolated zero energy astrophysical S-factor.
Using an independent experimental technique, the literature cross section data of 17O(p,g)18F is confirmed in the energy region of the resonances while lower direct capture cross section is recommended at higher energies. The present dataset provides a constraint for the theoretical cross sections.

G. Gyurky, A. Ornelas, Z. Fulop, et. al.
Fri, 10 Mar 17
7/52

Comments: Accepted for publication in Phys. Rev. C. Abstract shortened in order to comply with arxiv rules

# Dark matter in U(1) extensions of the MSSM with gauge kinetic mixing [CL]

The gauge kinetic mixing in general is allowed in models with multiple Abelian gauge groups. In this paper, we investigate the gauge kinetic mixing in the framework of $U(1)$ extensions of the MSSM. It enlarges the viable parameter space, and has an important effect on the particle mass spectrum as well as the $Z_2$ coupling with matters. The SM-like Higgs boson mass can be enhanced with a nonzero kinetic mixing parameter and the muon $g-2$ tension is less severe than in the case of no mixing. We present the results from both benchmark analysis and global parameter scan. Various theoretical and phenomenological constraints have been considered. The recent LHC searches for the $Z_2$ boson are important for the case of large positive kinetic mixing where the $Z_2$ coupling is enhanced, and severely constrain scenarios with $M_{Z_2} < 2.8$ TeV. The viable dark matter candidate predicted by the model is either the neutralino or the right-handed sneutrino. Cosmological constraints from dark matter searches play a significant role in excluding the parameter space. Portions of the parameter space with relatively low sparticle mass spectrum can be successfully explored in the LHC run-2 as well as future linear colliders and dark matter searches.

G. Belanger, J. Silva and H. Tran
Fri, 10 Mar 17
16/52

# Strong CP problem, axions, and cosmological implications of CP violation [CL]

In this talk, I present a pedagogical and historical review related to the CP symmetry. It includes the weak CP violation, the strong CP problem, “invisible” axions and cosmology, and Type-II leptogenesis.

J. Kim
Fri, 10 Mar 17
20/52

Comments: 21 pages of LaTeX file with 12 figures. Talk presented at Corfu, Greece

# Hydrodynamic turbulence in quasi-Keplerian rotating flows [CL]

We report a direct-numerical-simulation study of Taylor-Couette flow in the quasi-Keplerian regime at shear Reynolds numbers up to $\mathcal{O}(10^5)$. Quasi-Keplerian rotating flow has been investigated for decades as a simplified model system to study the origin of turbulence in accretion disks that is not fully understood. The flow in this study is axially periodic and thus the experimental end-wall effects on the stability of the flow are avoided. Using optimal linear perturbations as initial conditions, our simulations find no sustained turbulence: the strong initial perturbations distort the velocity profile and trigger turbulence that eventually decays.

L. Shi, B. Hof, M. Rampp, et. al.
Fri, 10 Mar 17
31/52

# A Reappraisal on Dark Matter Co-annihilating with a Top/Bottom Partner [CL]

We revisit the calculation of relic density of dark matter particles co-annihilating with a top or bottom partner, by properly including the QCD bound-states (onia) effects of the colored partners, as well as the relevant electroweak processes which become important in the low mass region. We carefully set up the complete framework that incorporates the relevant contributions and investigate their effects on the cosmologically preferred mass spectrum, which turn out to be comparable in size to those coming from the Sommerfeld enhancement. We apply the calculation to three scenarios: bino-stop and bino-sbottom co-annihilations in supersymmetry, and a vector dark matter co-annihilating with a fermionic top partner. In addition, we confront our analysis of the relic abundance with recent direct detection experiments and, in the case of bino-sbottom co-annihilation, collider searches at the LHC.

W. Keung, I. Low and Y. Zhang
Fri, 10 Mar 17
46/52

# On Kinetic Slow Modes, Fluid Slow Modes, and Pressure-Balanced Structures in the Solar Wind [CL]

Observations in the solar wind suggest that the compressive component of inertial-range solar-wind turbulence is dominated by slow modes. The low collisionality of the solar wind allows for non-thermal features to survive, which suggests the requirement of a kinetic plasma description. The least-damped kinetic slow mode is associated with the ion-acoustic (IA) wave and a non-propagating (NP) mode. We derive analytical expressions for the IA-wave dispersion relation in an anisotropic plasma in the framework of gyrokinetics and then compare them to fully-kinetic numerical calculations, results from two-fluid theory, and MHD. This comparison shows major discrepancies in the predicted wave phase speeds from MHD and kinetic theory at moderate to high $\beta$. MHD and kinetic theory also dictate that all plasma normal modes exhibit a unique signature in terms of their polarization. We quantify the relative amplitude of fluctuations in the three lowest particle velocity moments associated with IA and NP modes in the gyrokinetic limit and compare these predictions with MHD results and in-situ observations of the solar-wind turbulence. The agreement between the observations of the wave polarization and our MHD predictions is better than the kinetic predictions, suggesting that the plasma behaves more like a fluid in the solar wind than expected.

D. Verscharen, C. Chen and R. Wicks
Fri, 10 Mar 17
48/52

Comments: 8 pages, 5 figures, submitted to ApJ

# Sourcing Dark Matter and Dark Energy from $α$-attractors [CL]

Recently, Kallosh and Linde have drawn attention to a new family of superconformal inflationary potentials, subsequently called $\alpha$-attractors. The $\alpha$-attractor family can interpolate between a large class of inflationary models. It also has an important theoretical underpinning within the framework of supergravity. We demonstrate that the $\alpha$-attractors have an even wider appeal since they may describe dark matter and perhaps even dark energy. The dark matter associated with the $\alpha$-attractors, which we call $\alpha$-dark matter ($\alpha$DM), shares many of the attractive features of fuzzy dark matter, with $V(\varphi) = \frac{1}{2}m^2\varphi^2$, while having none of its drawbacks. Like fuzzy dark matter, $\alpha$DM can have a large Jeans length which could resolve the cusp-core and substructure problems faced by standard cold dark matter. $\alpha$DM also has an appealing tracker property which enables it to converge to the late-time dark matter asymptote, $\langle w\rangle \simeq 0$, from a wide range of initial conditions. It thus avoids the enormous fine-tuning problems faced by the $m^2\varphi^2$ potential in describing dark matter.

S. Mishra, V. Sahni and Y. Shtanov
Fri, 10 Mar 17
50/52

# High-mass twin stars with a multi-polytrope EoS [CL]

We show that in the 3-polytropes model of Hebeler et al. \cite{Hebeler:2013nza} for the neutron star equation of state at supersaturation densities a third family of compact stars can be obtained which confirms the possibility of high-mass twin stars that have coincident masses $M_1=M_2\approx 2~M_\odot$ and significantly different radii $|R_1-R_2|>2-3$ km. We consider a scenario of a first order phase transition which eliminates one of the three polytropes from the star structure and results in a sharp boundary between a high-density and low-density phase.

D. Alvarez-Castillo and D. Blaschke
Thu, 9 Mar 17
5/54

Comments: 4 pages, 2 figures, 1 table

# A review of gravitational waves from cosmic domain walls [CL]

In this contribution, we discuss the cosmological scenario where unstable domain walls are formed in the early universe and their late-time annihilation produces a significant amount of gravitational waves. After describing cosmological constraints on long-lived domain walls, we estimate the typical amplitude and frequency of gravitational waves observed today. We also review possible extensions of the standard model of particle physics that predict the formation of unstable domain walls and can be probed by observation of relic gravitational waves. It is shown that recent results of pulser timing arrays and direct detection experiments partially exclude the relevant parameter space, and that a much wider parameter space can be covered by the next generation of gravitational wave observatories.

K. Saikawa
Thu, 9 Mar 17
7/54

Comments: 25 pages, 4 figures, invited paper to special issue Gravitational Waves: Prospects after the First Direct Detections’ in Universe’

# Instabilities in Mimetic Matter Perturbations [CL]

We study cosmological perturbations in mimetic matter scenario with a general higher derivative function. We show that the model suffers from the ghost and the gradient instabilities. We perform the analysis in both comoving and Newtonian gauges and confirm that the Hamiltonians and the associated instabilities are consistent with each other in both gauges. The existence of instabilities is independent of the specific form of higher derivative function which generates gradients for mimetic field perturbations. It is verified that these instabilities are not associated with the higher derivative instabilities such as the Ostrogradsky ghost.

H. Firouzjahi, M. Gorji and A. Mansoori
Thu, 9 Mar 17
8/54

# Giant ripples on comet 67P/Churyumov-Gerasimenko sculpted by sunset thermal wind [CL]

Explaining the unexpected presence of dune-like patterns at the surface of the comet 67P/Churyumov-Gerasimenko requires conceptual and quantitative advances in the understanding of surface and outgassing processes. We show here that vapor flow emitted by the comet around its perihelion spreads laterally in a surface layer, due to the strong pressure difference between zones illuminated by sunlight and those in shadow. For such thermal winds to be dense enough to transport grains — ten times greater than previous estimates — outgassing must take place through a surface porous granular layer, and that layer must be composed of grains whose roughness lowers cohesion consistently with contact mechanics. The linear stability analysis of the problem, entirely tested against laboratory experiments, quantitatively predicts the emergence of bedforms in the observed wavelength range, and their propagation at the scale of a comet revolution. Although generated by a rarefied atmosphere, they are paradoxically analogous to ripples emerging on granular beds submitted to viscous shear flows. This quantitative agreement shows that our understanding of the coupling between hydrodynamics and sediment transport is able to account for bedform emergence in extreme conditions and provides a reliable tool to predict the erosion and accretion processes controlling the evolution of small solar system bodies.

P. Jia, B. Andreotti and P. Claudin
Thu, 9 Mar 17
11/54

Comments: 37 pages, 13 figures, 1 table

# Inflationary Dynamics with a Smooth Slow-Roll to Constant-Roll Era Transition [CL]

In this paper we investigate the implications of having a varying second slow-roll index on the canonical scalar field inflationary dynamics. We shall be interested in cases that the second slow-roll can take small values and correspondingly large values, for limiting cases of the function that quantifies the variation of the second slow-roll index. As we demonstrate, this can naturally introduce a smooth transition between slow-roll and constant-roll eras. We discuss the theoretical implications of the mechanism we introduce and we use various illustrative examples in order to better understand the new features that the varying second slow-roll index introduces. In the examples we will present, the second slow-roll index has exponential dependence on the scalar field, and in one of these cases, the slow-roll era corresponds to a type of $\alpha$-attractor inflation. Finally, we briefly discuss how the combination of slow-roll and constant-roll may lead to non-Gaussianities in the primordial perturbations.

S. Odintsov and V. Oikonomou
Thu, 9 Mar 17
33/54

# Reconstruction of extended inflationary potentials for attractors [CL]

We give the procedure to reconstruct the extended inflationary potentials for general scalar-tensor theory of gravity and use the $\alpha$ attractor and the constant slow-roll model as examples to show how to reconstruct the class of extended inflationary potentials in the strong coupling limit. The class of extended inflationary potentials have the same attractor in the strong coupling limit, and the reconstructed extended inflationary potentials are consistent with the observational constraints. We also derive the condition on the coupling constant $\xi$ for satisfying the strong coupling.

Q. Gao and Y. Gong
Thu, 9 Mar 17
41/54

# Über-Gravity and the Cosmological Constant Problem [CL]

Recently, the idea of taking ensemble average over gravity models has been introduced. Based on this idea, we study the ensemble average over (effectively) all the gravity models dubbing the name \”ubergravity. The \”ubergravity has interesting universal properties, independent from the choice of basis: $i)$ it mimics Einstein-Hilbert gravity for high-curvature regime, $ii)$ it predicts stronger gravitational force for an intermediate-curvature regime, $iii)$ surprisingly, for low-curvature regime, i.e. $R<R_0$ where $R$ is Ricci scalar and $R_0$ is a given scale, the Lagrangian vanishes automatically and $iiii)$ there is a sharp transition between low- and intermediate-curvature regimes at $R=R_0$. We show that the \”ubergravity response is robust to any value of the vacuum energy, $\rho_{vac}$. This means the response to any non-vanishing value of $\rho_{vac}$ gives an exact deSitter solution where $R_0$ plays the role of the cosmological constant. Consequently, $R_0$ should be fixed by the observations and there is no need to fine-tune the cosmological constant.

N. Khosravi
Wed, 8 Mar 17
21/60

# Cosmology and Convention [CL]

I argue that some important elements of the current cosmological model are “conventionalist” in the sense defined by Karl Popper.

D. Merritt
Wed, 8 Mar 17
44/60

# Plasma turbulence at ion scales: a comparison between PIC and Eulerian hybrid-kinetic approaches [CL]

Kinetic-range turbulence in magnetized plasmas and, in particular, in the context of solar-wind turbulence has been extensively investigated over the past decades via numerical simulations. Among others, one of the widely adopted reduced plasma model is the so-called hybrid-kinetic model, where the ions are fully kinetic and the electrons are treated as a neutralizing (inertial or massless) fluid. Within the same model, different numerical methods and/or approaches to turbulence development have been employed. In the present work, we present a comparison between two-dimensional hybrid-kinetic simulations of plasma turbulence obtained with two complementary approaches spanning about two decades in wavenumber – from MHD inertial range to scales well below the ion gyroradius – with a state-of-the-art accuracy. One approach employs hybrid particle-in-cell (HPIC) simulations of freely-decaying Alfv\’enic turbulence, whereas the other consists of Eulerian hybrid Vlasov-Maxwell (HVM) simulations of turbulence continuously driven with partially-compressible large-scale fluctuations. Despite the completely different initialization and injection/drive at large scales, the same properties of turbulent fluctuations at $k_\perp\rho_i\gtrsim1$ are observed. The system indeed self-consistently “reprocesses” the turbulent fluctuations while they are cascading towards smaller and smaller scales, in a way which actually depends on the plasma beta parameter. Small-scale turbulence has been found to be mainly populated by kinetic Alfv\’en wave (KAW) fluctuations for $\beta\geq1$, whereas KAW fluctuations are only sub-dominant for low-$\beta$.

S. Cerri, L. Franci, F. Califano, et. al.
Wed, 8 Mar 17
47/60

Comments: 18 pages, 4 figures, accepted for publication in J. Plasma Phys. (Collection: “The Vlasov equation: from space to laboratory plasma physics”)

# Unitary NEC violation in P(X) cosmologies [CL]

A non-singular cosmological bounce in the Einstein frame can only take place if the Null Energy Condition (NEC) is violated. We explore situations where a single scalar field drives the NEC violation and derive the constraints imposed by demanding tree level unitarity on a cosmological background. We then focus on the explicit constraints that arise in P(X) theories and show that constraints from perturbative unitarity make it impossible for the NEC violation to occur within the region of validity of the effective field theory without also involving irrelevant operators that arise at a higher scale that would enter from integrating out more massive degrees of freedom. Within the context of P(X) theories we show that including such operators allows for a bounce that does not manifestly violate tree level unitarity, but at the price of either imposing a shift symmetry or involving technically unnatural small operator coefficients within the low-energy effective field theory.

C. Rham and S. Melville
Wed, 8 Mar 17
51/60

# Scalar and vector Galileons [CL]

An alternative for the construction of fundamental theories is the introduction of Galileons. These are fields whose action leads to non higher than second-order equations of motion. As this is a necessary but not sufficient condition to make the Hamiltonian bounded from below, as long as the action is not degenerate, the Galileon construction is a way to avoid pathologies both at the classical and quantum levels. Galileon actions are, therefore, of great interest in many branches of physics, specially in high energy physics and cosmology. This proceedings contribution presents the generalities of the construction of both scalar and vector Galileons following two different but complimentary routes.

Y. Rodriguez and A. Navarro
Tue, 7 Mar 17
2/66

Comments: LaTeX file in jpconf style, 12 pages, no figures. To be published in Journal of Physics: Conference Series as the proceedings of the 70&70 Classical and Quantum Gravitation Party: Meeting with Two Latin American Masters on Theoretical Physics (Cartagena de Indias – Colombia, 28th-30th September, 2016)

# Quantum Nuclear Pasta and Nuclear Symmetry Energy [CL]

Complex and exotic nuclear geometries are expected to appear naturally in dense nuclear matter found in the crust of neutron stars and supernovae environment collectively referred to as nuclear pasta. The pasta geometries depend on the average baryon density, proton fraction and temperature and are critically important in the determination of many transport properties of matter in supernovae and the crust of neutron stars. Using a set of self-consistent microscopic nuclear energy density functionals we present the first results of large scale quantum simulations of pasta phases at baryon densities $0.03 \leq \rho \leq 0.10$ fm$^{-3}$, proton fractions $0.05 \leq Y_p \leq 0.40$, and zero temperature. The full quantum simulations, in particular, allow us to thoroughly investigate the role and impact of the nuclear symmetry energy on pasta configurations. We use the Sky3D code that solves the Skyrme Hartree-Fock equations on a three-dimensional Cartesian grid. For the nuclear interaction we use the state of the art UNEDF1 parametrization, which was introduced to study largely deformed nuclei, hence is suitable for studies of the nuclear pasta. Density dependence of the nuclear symmetry energy is simulated by tuning two purely isovector observables that are insensitive to the current available experimental data. We find that a minimum total number of nucleons $A=2000$ is necessary to prevent the results from containing spurious shell effects and to minimize finite size effects. We find that a variety of nuclear pasta geometries are present in the neutron star crust and the result strongly depends on the nuclear symmetry energy. The impact of the nuclear symmetry energy is less pronounced as the proton fractions increase. Quantum nuclear pasta calculations at $T=0$ MeV are shown to get easily trapped in meta-stable states, and possible remedies to avoid meta-stable solutions are discussed.

F. Fattoyev, C. Horowitz and B. Schuetrumpf
Tue, 7 Mar 17
3/66

Comments: 23 pages, 18 figures, 8 tables