Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session L14: Dark Matter, Inflation and Phase TransitionsLive
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Sponsoring Units: DPF Chair: Marc Sher, William & Mary Room: Virginia A |
Sunday, April 19, 2020 3:30PM - 3:42PM Live |
L14.00001: The Dodelson-Widrow Mechanism In the Presence of Self-Interacting Neutrinos Walter Tangarife, Andre de Gouvea, Manibrata Sen, Yue Zhang keV-scale gauge-singlet fermions, allowed to mix with the active neutrinos, are elegant dark matter(DM) candidates. They are produced in the early universe via the Dodelson-Widrow mechanism and can be detected as they decay very slowly, emitting X-rays. In the absence of new physics, this hypothesis is virtually ruled out by astrophysical observations. Here, we show that new interactions among the active neutrinos allow these sterile neutrinos to make up all the DM while safely evading all current experimental bounds. The existence of these new neutrino interactions may manifest itself in next-generation experiments, including DUNE. [Preview Abstract] |
Sunday, April 19, 2020 3:42PM - 3:54PM Live |
L14.00002: Beyond the Isotropic Lifshitz Endpoint -- Antiscreening, Dark Matter, Cosmic Evolution Tien Chang We consider symmetry breakings beyond the admissible range of isotropic Lifshitz fixed points in renormalization-group calculations. Such phenomenon is akin to the well-known result of tricritical-tricoexistence effect of phase transitions. The isotropic Lifschitz endpoint (ILE) is the critical point of the statistically isotropic multiphase coexisting states of subdomains of anisotropic helicoidal and non-helicoidal neighborhoods. An example of cosmic evolution based on the effective action with scale-running gravitational and cosmological constants at large spatial scales is considered. The gravitational symmetry-breaking effects at intermediate (e.g., galactic) scales are related to the development and formation of cosmic structures with multifractal, antiscreening and dark matter effects. At very large cosmological scales, the FLRW formulism leads to the understanding of statistically isotropic multi-phase coexisting states. We presently live in a matter-dominated statistically isotropic and homogeneous fractal Universe far beyond the ILE. The result provides a natural explanation for the accelerating cosmic expansion and coincidence problem. [Preview Abstract] |
Sunday, April 19, 2020 3:54PM - 4:06PM Live |
L14.00003: Baryogenesis and Dark Matter from Freeze-In Brian Shuve, David Tucker-Smith We propose a model in which the baryon asymmetry and dark matter are created via the decays and inverse decays of QCD-charged scalars, at least one of which must be in the TeV mass range. Singlet fermions produced in their decays constitute the dark matter. The singlets never reach equilibrium, and their coherent production, propagation, and annihilation generates a baryon asymmetry. We find that that the out-of-equilibrium condition and the dark matter density constraint typically require the lightest scalar to be long-lived, giving good prospects for detection or exclusion in current and upcoming colliders. In generalizing the leptogenesis mechanism of Akhmedov, Rubakov and Smirnov, our model expands the phenomenological possibilities for low-scale baryogenesis. [Preview Abstract] |
Sunday, April 19, 2020 4:06PM - 4:18PM Live |
L14.00004: Cosmological Phase Transition of Spontaneous Confinement Majid Ekhterachian, Kaustubh Agashe, Peizhi Du, Soubhik Kumar, Raman Sundrum The dynamics of a cosmological (de)confinement phase transition is studied in nearly conformally invariant field theories, where confinement is predominantly spontaneously generated and associated with a light “dilaton” field. We show how the leading contribution to the transition rate can be computed within the dilaton effective theory. In the context of Composite Higgs theories, we demonstrate that a simple scenario involving two renormalization-group fixed points can make the transition proceed much more rapidly than in the minimal scenario, thereby avoiding excessive dilution of matter abundances generated before the transition. The implications for gravitational wave phenomenology are discussed. [Preview Abstract] |
Sunday, April 19, 2020 4:18PM - 4:30PM On Demand |
L14.00005: Spectator Dark Matter Tommi Tenkanen The observed dark matter (DM) abundance in the Universe can be fully accounted for by a minimally coupled spectator scalar field that was light during cosmic inflation. In this scenario, dark matter was produced during inflation by amplification of quantum fluctuations of the spectator field. I will discuss the production mechanism in detail, as well as the DM isocurvature perturbations that are unavoidably generated in such scenarios and the circumstances under which they are not problematic for the viability of non-thermal DM models. I will also discuss implications of DM isocurvature for structure formation, showing that the model has interesting consequences which allow one to test the scenario. [Preview Abstract] |
Sunday, April 19, 2020 4:30PM - 4:42PM |
L14.00006: A multicomponent dark matter scenario consistent with experiment Roland Allen, Reagan Thornberry, Maxwell Throm, John Killough, Dylan Blend, Michael Erickson, Brian Sun, Brett Bays, Gabriel Frohaug We propose a dark matter scenario which is ideal in the sense that (1) all of the well-known successes of supersymmetry are preserved, (2) the parameters can satisfy naturalness, (3) the addition of an extended Higgs sector implies a doubly rich plethora of new particles and new physics to be discovered, (4) the mass of the dominant dark matter WIMP is $\le 125$ GeV/c$^2$, (5) the gauge couplings of this particle are precisely defined, and (6) naturalness implies a limited range for its Higgs-mediated couplings. The firm prediction of $\le 125$ GeV/c$^2$ for the mass of the dominant dark matter particle would have been disconfirmed if the positron excess observed by AMS-02 were evidence of a dark matter particle at $\sim 800$ GeV or higher, but this interpretation has itself been disconfirmed by Planck observations. The predicted mass is, on the other hand, consistent with both the Planck results and several independent analyzes of $\gamma$-ray and antiproton excesses from the Fermi-LAT and AMS-02 experiments, respectively, all of which imply masses of $\sim 100$ GeV/c$^2$ or less if the origin is dark matter annihilation. [Preview Abstract] |
Sunday, April 19, 2020 4:42PM - 4:54PM |
L14.00007: Resolving the CMB Anisotropies using the variable physical constants approach. Rajendra Gupta The resolution of the Cosmic Microwave Background anisotropies by the $\Lambda $CDM model is considered the key reason why this model is so universally adopted by most cosmologists. We have shown that the CMB anisotropies can also be explained using variable physical constants approach without requiring the cosmological constant $\Lambda $. With this approach, the position of the first peak in the observed angular power spectrum of CMB has the multipole moment value of \textit{229} using the redshift $z=$\textit{1090}, i.e. the same as observed and as determined by the $\Lambda $CDM models. The same approach recently was used to resolve the flatness problem and to show that the universe is negatively curved$^{\mathrm{1}}$. The approach also resolved three astrometric anomalies and fitted the most up-to-date supernovae Ia data better than the $\Lambda $CDM model$^{\mathrm{2}}$. Now, by correctly estimating the multipole moment of the fundamental mode in the CMB anisotropy, the new approach has reached another milestone to establish that the speed of light varies as $c=c_{0}$\textit{/(1}$+z)^{1.8}$ and the gravitational constant varies as $G=G_{0}$\textit{/(1}$+z)^{5.4}$. Other physical constants are also evolutionary$^{\mathrm{2}}$. The universe is negatively curved with curvature $R_{c}=R_{c,0}$\textit{/(1}$+z)^{3.3}$ where $R_{c,0}=$\textit{1.64c}$_{0}/H_{0} $and $H_{0}$ is the Hubble constant$^{\mathrm{1}}$. $^{\mathrm{1}}$ R. P. Gupta, \textit{Galaxies} \textbf{7}, 77 (2019); $^{\mathrm{2}}$ Ibid 55. [Preview Abstract] |
Sunday, April 19, 2020 4:54PM - 5:06PM Not Participating |
L14.00008: Beyond Standard Model Decays During the Big Bang Nucleosynthesis Epoch Chad Kishimoto, Hannah Rasmussen, Alex McNichol In this talk, we explore Beyond Standard Model (BSM) physics models of out-of-equilibrium particle decay in the early universe around the time of Big Bang Nucleosynthesis (BBN). In particular, we look into the decay of massive neutral fermions (e.g., ``sterile neutrinos'') into Standard Model particles that will heat the photon-electron-positron-baryon plasma during the BBN epoch, diluting decoupled particles, and will produce non-thermal high-energy neutrinos of all flavors. By considering both the production and scattering of these high-energy neutrinos, we investigate the observable consequences of this process in cosmological observables such as the number of relativistic degrees of freedom ($N_{\rm eff}$) and the sum of the neutrino mass, and discuss the possible effects of changing the time-temperature relation and an non-thermal high-energy distribution of neutrinos and anti-neutrinos on BBN yields. [Preview Abstract] |
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