Magnetic monopole mass bounds from heavy ion collisions and neutron stars [CL]

Magnetic monopoles, if they exist, would be produced amply in strong magnetic fields and high temperatures via the thermal Schwinger process. Such circumstances arise in heavy ion collisions and in neutron stars, both of which imply lower bounds on the mass of possible magnetic monopoles. In showing this, we construct the cross section for pair production of magnetic monopoles in heavy ion collisions, which indicates that they are particularly promising for experimental searches such as MoEDAL.

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O. Gould and A. Rajantie
Mon, 22 May 17

Comments: 6 pages, 1 figure

Standard Model – Axion – Seesaw – H portal inflation [CL]

Extending the Standard Model with a new complex singlet scalar, right-handed neutrinos and a vector-like quark allows to simultaneously tackle several problems in particle physics and cosmology within a constrained framework that can be falsified by future probes of the cosmic microwave background, as well as by upcoming axion experiments. This Standard Model – Axion – Seesaw – H portal inflation theory (SMASH) provides predictive inflation and $H$ boson stabilization, and can explain baryogenesis, light neutrino masses, dark matter and the strong CP problem. The model contains a unique new mass scale which coincides with the axion decay constant, and also sets the scale for perturbative lepton-number violation processes. Testable predictions include a minimum value of the tensor-to-scalar ratio of $r\gtrsim 0.004$, a running of the spectral index $\alpha\gtrsim-8\times10^{-4}$, a change $\delta N_{\rm eff}\sim 0.03$ in the number of effective relativistic neutrinos, and an axion mass in the range $50\mu eV\leq m_A \leq 200 \mu eV$.

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C. Tamarit
Mon, 22 May 17

Comments: 8 pages, 2 figures, Contribution to the proceedings of the 52nd Rencontres de Moriond conference, Electroweak session, La Thuile (Italy) 2017

Sgoldstino-less inflation and low energy SUSY breaking [CL]

We assess the range of validity of sgoldstino-less inflation in a scenario of low energy supersymmetry breaking. We first analyze the consistency conditions that an effective theory of the inflaton and goldstino superfields should satisfy in order to be faithfully described by a sgoldstino-less model. Enlarging the scope of previous studies, we investigate the case where the effective field theory cut-off, and hence also the sgoldstino mass, are inflaton-dependent. We then introduce a UV complete model where one can realize successfully sgoldstino-less inflation and gauge mediation of supersymmetry breaking, combining the alpha-attractor mechanism and a weakly coupled model of spontaneous breaking of supersymmetry. In this class of models we find that, given current limits on superpartner masses, the gravitino mass has a lower bound of the order of the MeV, i.e. we cannot reach very low supersymmetry breaking scales. On the plus side, we recognize that in this framework, one can derive the complete superpartner spectrum as well as compute inflation observables, the reheating temperature, and address the gravitino overabundance problem. We then show that further constraints come from collider results and inflation observables. Their non trivial interplay seems a staple feature of phenomenological studies of supersymmetric inflationary models.

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R. Argurio, D. Coone, L. Heurtier, et. al.
Mon, 22 May 17

Comments: 40 pages, 4 figures

Constraints on direction-dependent cosmic birefringence from Planck polarization data [CEA]

Cosmic birefringence is the process that rotates the plane of polarization by an amount, $\alpha$, as photons propagate through free space. Such an effect arises in parity-violating extensions to the electromagnetic sector, such as the Chern-Simons term common in axion models, quintessence models, or Lorentz-violating extensions to the standard model. Most studies consider the monopole of this rotation, but it is also possible for the effect to have spatial anisotropies. Paying particular attention to large scales, we implement a novel pixel-based method to extract the spherical harmonics for $L \le 30$ and a pseudo-$C_L$ method for $L > 30$. Our results are consistent with no detection and we set 95% upper limits on the amplitude of a scale-invariant power spectrum of $L(L+1)C_L/2\pi < [2.9\, (\mathrm{stat.})\, \pm 0.7\, (\mathrm{syst.})]\times10^{-5} = [0.09\, (\mathrm{stat.}) \pm 0.02\, (\mathrm{syst.})] \,\mathrm{deg}^2$, on par with previous constraints. This implies specific limits on the dipole and quadrupole amplitudes to be $\sqrt{C_1/4\pi} < 0.2^\circ$ and $\sqrt{C_2/4\pi} < 0.1^\circ$, at 95% CL, respectively, improving previous constraints by an order of magnitude. We further constrain a model independent $M=0$ quadrupole in an arbitrary direction to be $\alpha_{20} = 0.02^\circ \pm 0.21^\circ$, with an unconstrained direction. However, we find an excess of dipolar power with an amplitude $\sqrt{3C_1/4\pi} = 0.32^\circ \pm 0.10^\circ\, (\mathrm{stat.})\, \pm 0.08^\circ\, (\mathrm{syst.})$ in the direction $(l, b) = (295^\circ, 17^\circ) \pm (22^\circ, 17^\circ)\, (\mathrm{stat.})\, \pm (5^\circ, 16^\circ)\, (\mathrm{syst.})$ larger than 1.4% of simulations with no birefringence. We attribute part of this signal to the contamination of residual foregrounds not accounted for in our simulations, though it should be further investigated.

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D. Contreras, P. Boubel and D. Scott
Fri, 19 May 17

Comments: 18 pages, 6 figures, 3 tables

Enhanced stellar neutrino emissivities in annihilating Coy Dark Matter [CL]

We calculate neutrino emissivities for annihilating Dark Matter with pseudoscalar-mediated couplings to ordinary matter in dense stellar environments. We show that for Dark Matter models compatible with current direct detection limits and cosmological relic abundance, the neutrino production rates from channels $\chi \chi \rightarrow \nu \nu$ or via pseudoscalar mediators $\chi \chi \rightarrow a a$ with subsequent decay $ a \rightarrow \nu \nu$, can be locally much stronger than the modified URCA processes at early stages of star cooling. In light of these results we discuss the parameter ranges and thermodynamical stellar conditions that could give rise to inner temperature profiles warmer than those obtained for standard scenarios, having thus an impact on possible superfluid components in the inner core.

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M. Cermeno, M. Perez-Garcia and R. Lineros
Fri, 19 May 17

Comments: 5 pages, 2 figures, and 1 table. Comments welcome

On the Inflationary Perturbations of Massive Higher-Spin Fields [CL]

Cosmological perturbations of massive higher-spin fields are generated during inflation, but they decay on scales larger than the Hubble radius as a consequence of the Higuchi bound. By introducing suitable couplings to the inflaton field, we show that one can obtain statistical correlators of massive higher-spin fields which remain constant or decay very slowly outside the Hubble radius. This opens up the possibility of new observational signatures from inflation.

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A. Kehagias and A. Riotto
Fri, 19 May 17

Comments: 22 pages

The $H_0$ tension in light of vacuum dynamics in the Universe [CEA]

Despite the outstanding achievements of modern cosmology, the classical dispute on the precise value of $H_0$, which is the first ever parameter of modern cosmology and one of the prime parameters in the field, still goes on and on after over half a century of measurements. Recently the dispute came to the spotlight with renewed strength owing to the significant tension (at $>3\sigma$ c.l.) between the latest Planck determination obtained from the cosmic microwave background (CMB) anisotropies and the local measurement from the Hubble Space Telescope, based on Cepheid variables. In this Letter, we investigate the impact of the dynamical vacuum models (DVMs) on such a controversy. These models have been recently explored in great detail by us, see e.g. arXiv:1602.02103 and arXiv:1703.08218, where it is shown that by letting the vacuum energy to support a mild dynamical dependence on the cosmic expansion it is possible to strongly ameliorate the quality fit to the overall $SNIa+BAO+H(z)+LSS+CMB$ cosmological observations, as compared to the concordance $\Lambda$CDM model. Here we show that the main DVMs can still surpass the $\Lambda$CDM fit even after including the local measurement of $H_0$, but our analysis definitely favors the CMB value. We find that even allowing a departure from the vacuum equation of state, the vacuum option $w=-1$ continues to be preferred. The kind of cosmic vacuum that is favored, however, is not the traditional cosmological constant but a mildly evolving one, $\rho_\Lambda(H(t))$, as indicated above. The large scale structure (LSS) formation data play a momentous role in discriminating among the two options.

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J. Sola, A. Gomez-Valent and J. Perez
Fri, 19 May 17

Comments: 7 pages, 3 figures and 3 tables