Naturalness in Higgs inflation in a frame independent formalism [CEA]

http://arxiv.org/abs/1403.3219


We make use of the frame and gauge independent formalism for scalar and tensor cosmological perturbations developed in Ref. [1] to show that the physical cutoff for 2-to-2 tree level scatterings in Higgs inflation is above the Planck scale M_P throughout inflation. More precisely, we found that in the Jordan frame, the physical cutoff scale is $({\Lambda}/a)_J \gtrsim \sqrt{M_P^2+{\xi}{\phi}^2}$, while in the Einstein frame it is $({\Lambda}/a)_J \gtrsim M_P$, where $\xi$ is the nonminimal coupling and $\phi$ denotes the Higgs vev during inflation. The dimensionless ratio of the physical cutoff to the relevant Planck scale is equal to one in both frames, thus demonstrating the physical equivalence of the two frames. Our analysis implies that Higgs inflation is unitary up to the Planck scale, and hence there is no naturalness problem in Higgs inflation. In this paper we only consider the graviton and scalar interactions.

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T. Prokopec and J. Weenink
Fri, 14 Mar 14
1/46

SDSSJ143244.91+301435.3: a link between radio-loud narrow-line Seyfert 1 galaxies and compact steep-spectrum radio sources? [GA]

http://arxiv.org/abs/1403.3229


We present SDSSJ143244.91+301435.3, a new case of radio-loud narrow line Seyfert 1 (RL NLS1) with a relatively high radio power (P1.4GHz=2.1×10^25 W Hz^-1) and large radioloudness parameter (R1.4=600+/-100). The radio source is compact with a linear size below ~1.4 kpc but, contrary to most of the RL NLS1 discovered so far with such a high R1.4, its radio spectrum is very steep (alpha=0.93) and not supporting a ‘blazar-like’ nature. Both the small mass of the central super-massive black-hole and the high accretion rate relative to the Eddington limit estimated for this object (3.2×10^7 Msun and 0.27, respectively, with a formal error of ~0.4 dex on both quantities) are typical of the class of NLS1. Through a modeling of the spectral energy distribution of the source we have found that the galaxy hosting SDSSJ143244.91+301435.3 is undergoing a quite intense star-formation (SFR=50 Msun y^-1) which, however, is expected to contribute only marginally (~1 per cent) to the observed radio emission. The radio properties of SDSSJ143244.91+301435.3 are remarkably similar to those of compact steep spectrum (CSS) radio sources, a class of AGN mostly composed by young radio galaxies. This may suggest a direct link between these two classes of AGN, with the CSS sources possibly representing the misaligned version (the so-called parent population) of RL NLS1 showing blazar characteristics.

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A. Caccianiga, S. Anton, L. Ballo, et. al.
Fri, 14 Mar 14
3/46

The Minimal Volkov – Akulov – Starobinsky Supergravity [CL]

http://arxiv.org/abs/1403.3269


We construct a supergravity model whose scalar degrees of freedom arise from a chiral superfield and are solely a scalaron and an axion that is very heavy during the inflationary phase. The model includes a second chiral superfield $X$, which is subject however to the constraint $X^2=0$ so that it describes only a Volkov – Akulov goldstino and an auxiliary field. We also construct the dual higher – derivative model, which rests on a chiral scalar curvature superfield ${\cal R}$ subject to the constraint ${\cal R}^2=0$, where the goldstino dual arises from the gauge – invariant gravitino field strength as $\gamma^{mn} {\cal D}_m \psi_n$. The final bosonic action is an $R+R^2$ theory involving an axial vector $A_m$ that only propagates a physical pseudoscalar mode.

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I. Antoniadis, E. Dudas, S. Ferrara, et. al.
Fri, 14 Mar 14
5/46

Ionized gas disks in Elliptical and S0 galaxies at $z<1$ [GA]

http://arxiv.org/abs/1403.3104


We analyse the extended, ionized-gas emission of 24 early-type galaxies (ETGs) at $0<z<1$ from the ESO Distant Cluster Survey (EDisCS). We discuss different possible sources of ionization and favour star-formation as the main cause of the observed emission. Ten galaxies have disturbed gas kinematics, while 14 have rotating gas disks. In addition, 15 galaxies are in the field, while 9 are in the infall regions of clusters. This implies that, if the gas has an internal origin, this is likely stripped as the galaxies get closer to the cluster centre. If the gas instead comes from an external source, then our results suggest that this is more likely acquired outside the cluster environment, where galaxy-galaxy interactions more commonly take place. We analyse the Tully-Fisher relation of the ETGs with gas disks, and compare them to EDisCS spirals. Taking a matched range of redshifts, $M_{B}<-20$, and excluding galaxies with large velocity uncertainties, we find that, at fixed rotational velocity, ETGs are 1.7 mag fainter in $M_{B}$ than spirals. At fixed stellar mass, we also find that ETGs have systematically lower specific star-formation rates than spirals. This study constitutes an important step forward towards the understanding of the evolution of the complex ISM in ETGs by significantly extending the look-back-time baseline explored so far.

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Y. Jaffe, A. Aragon-Salamanca, B. Ziegler, et. al.
Fri, 14 Mar 14
6/46

Inequivalence of Coset Constructions for Spacetime Symmetries [CL]

http://arxiv.org/abs/1403.3095


Non-linear realizations of spacetime symmetries can be obtained by a generalization of the coset construction valid for internal ones. The physical equivalence of different representations for spacetime symmetries is not obvious, since their relation involves not only a redefinition of the fields but also a field-dependent change of coordinates. A simple and relevant spacetime symmetry is obtained by the contraction of the 4D conformal group that leads to the Galileon group. We analyze two non-linear realizations of this group, focusing in particular on the propagation of signals around non-trivial backgrounds. The aperture of the lightcone is in general different in the two representations and in particular a free (luminal) massless scalar is mapped in a Galileon theory which admits superluminal propagation. We show that in this theory, if we consider backgrounds that vanish at infinity, there is no asymptotic effect: the displacement of the trajectory integrates to zero, as can be expected since the S-matrix is trivial. Regarding local measurements, we show that the puzzle is solved taking into account that a local coupling with fixed sources in one theory is mapped into a non-local coupling and we show that this effect compensates the different lightcone. Therefore the two theories have a different notion of locality. The same applies to the different non-linear realizations of the conformal group and we study the particular case of a cosmologically interesting background: the Galilean Genesis scenarios.

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P. Creminelli, M. Serone, G. Trevisan, et. al.
Fri, 14 Mar 14
11/46

A Technique to Search for High Mass Dark Matter Axions [CL]

http://arxiv.org/abs/1403.3121


Axions are a well motivated dark matter candidate. Microwave cavity experiments have been shown to be sensitive to axions in the mass range 1 $\mu$eV to 40 $\mu$eV, but face challenges searching for axions with larger masses. We propose a technique using a microwave Fabry-P\'{e}rot resonator and a series of current-carrying wire planes that can be used to search for dark matter axions with masses above 40 $\mu$eV. This technique retains the advantages of the microwave cavity search technique but allows for large volumes and high $Q$s at higher frequencies.

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G. Rybka and A. Wagner
Fri, 14 Mar 14
12/46

Multiwavelength investigations of co-evolution of bright custer galaxies [CEA]

http://arxiv.org/abs/1403.3168


We report a systematic multi-wavelength investigation of environments of the brightest cluster galaxies (BCGs), using the X-ray data from the Chandra archive, and optical images taken with 34’x 27′ field-of-view Subaru Suprime-Cam. Our goal is to help understand the relationship between the BCGs and their host clusters, and between the BCGs and other galaxies, to eventually address a question of the formation and co-evolution of BCGs and the clusters.
Our results include: 1) Morphological variety of BCGs, or the second or the third brightest galaxy (BCG2, BCG3), is comparable to that of other bright red sequence galaxies, suggesting that we have a continuous variation of morphology between BCGs, BCG2, and BCG3, rather than a sharp separation between the BCG and the rest of the bright galaxies. 2) The offset of the BCG position relative to the cluster centre is correlated to the degree of concentration of cluster X-ray morphology (Spearman rho = -0.79), consistent with an interpretation that BCGs tend to be off-centered inside dynamically unsettled clusters. 3) Morphologically disturbed clusters tend to harbour the brighter BCGs, implying that the “early collapse” may not be the only major mechanism to control the BCG formation and evolution.

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Y. Hashimoto, J. Henry and H. Boehringer
Fri, 14 Mar 14
18/46