Session T13: Dark Energy and Dark Matter

Live

Many parameterizations of couplings between dark energy (DE) and dark matter (DM) as fluids in the continuity equation have been studied in the literature, and observational data from the growth of perturbations can constrain these parameterizations. Instead, we present here a study of DE-DM coupling as fields, making use of the Boltzmann transport equation. This calculation required obtaining a distribution function for dark energy that leads to an equation of state parameter that is negative, which neither Bose-Einstein nor Fermi-Dirac statistics can supply. Treating dark energy as a quantum scalar field, we use adiabatic subtraction to obtain a finite analytic approximation for its distribution function that assumes the FLRW metric and nothing more. We present and examine our results for coupling via the graviton with no other explicit coupling in the Lagrangian. We then will fit the coupling parameter to supernovae and CMB data using COSMOMC.   

Live

In recent years, models that explain dark energy have been extensively studied. These models include scalar-tensor models such as quintessence, tachyons, and k-essence. The Chaplygin gas model is another interesting class of dark energy models that assumes the universe is full of a peculiar perfect fluid. It is important to note that in addition to describing the dark energy, scalar-tensor models and the Chaplygin gas model can explain the cosmological spherical collapse. In this talk, we use the Chaplygin gas model to describe the spherical collapse of the cosmological structures. To this end, we study the scalar quintessence model with especial potential and show this model is equivalent to the Chaplygin gas model. Then, by solving the overdensity evolution equation, we obtain all the parameters of the spherical collapse model. Based on the results, we claim that the formation of the large scale structures occurs earlier than predicted in the standard cosmological model. Then, we investigate the spherical collapse model in the framework of the tachyon scalar model with constant potential and obtain similar results.   

Live

We investigate possible top quark spin correlation effects in Dark Matter (DM) production in association with a single top quark at the LHC in the context of Simplified Models where spin-0 and spin-1 particles mediate the interactions between the Standard Model (SM) sector and the DM sector. We discuss in detail the results of angular correlations and distributions of the top quark which may allows us to explore and establish constraints on the DM and SM interactions at the LHC.   

Live

We observe damped temporal oscillations in the scale factor of the universe at a dominant frequency of \textasciitilde 7 cycles/Hubble-time in the recent Pantheon Compilation of 1048 type Ia supernovae (SNe). The residual oscillations observed in the Pantheon data closely matches and reaffirms our initial observation of oscillations from earlier SNe data (SNLS3, 2011). The observed signal amplitude is at 3 sigma. Our model describing the oscillations is a simple scalar field harmonic oscillator coupled to the LCDM Friedmann equation, but carried into the present epoch. The scalar field energy density takes over the role of the dark matter energy density in LCDM cosmology, fits LCDM well, and matches the present dark matter density parameter. Our model fits the observed signal in frequency, phase and damping, but is a factor of 2 too small in amplitude. The amplitude could be increased by including parametric resonance.   

Live

We perform direct numerical simulations of magnetohydrodynamic turbulence in the early universe and numerically compute the resulting stochastic background of gravitational waves and relic magnetic fields. We obtain realistic kinetic and magnetic energy spectra, not considered in earlier analytic models. The computed gravitational wave spectra have a new universal form at low frequencies, with more power than suggested by earlier analytical models. The efficiency of gravitational wave production varies significantly with the physical form of the turbulence. For given energy in the turbulence, we find that the gravitational wave signal is stronger for irrotational flows than for vortical ones. Our results predict the details of gravitational wave spectra generated during the radiation-dominated epoch of the universe. They may be detectable in the stochastic gravitational wave background with the planned Laser Interferometer Space Antenna. This would lead to the understading of cosmological phase transition physics, which can have consequences on the baryon asymmetry problem and on the origin seed of observed magnetic fields coherent over very large scales at the present time. This work is based on the publications arXiv:1807.05479 and arXiv: 1903.08585.   

Live

Within the literature, many different parameters of couplings between dark energy (DE) and dark matter (DM) as fluids in the continuity equation have been studied and examined, and observational data can further constrain these parameterizations. Instead of a fluid coupling, we present here a study of DE-DM coupling as fields, and utilize the Boltzmann transport equation. In calculating the Boltzmann transport, we required obtaining a distribution function for DE that leads to an equation of state parameter that is negative, which neither Bose-Einstein nor Fermi-Dirac statistics can supply. From quantum field theory in curved spacetime, we calculated an effective distribution function that accounted for our negative state parameter. We present and examine our results for a Yukawa-type coupling with a provided graphical figure of the interaction that is found within the continuity equation. Then, we will fit the coupling parameter to supernovae and CMB data using COSMOMC.   

Dark Matter and Surplus Quarks (for Baryons) Generated by Oblique Confinement of Quarks

For surplus quarks (and baryons) to emerge after Big Bang, a nonequilibrium binding and superconductor-like condensation of quark-antiquark pairs must occur before the electroweak (EW) symmetry breakdown (similar for leptons). As shown here, the formerly unknown dimensionless coupling to the Ginsburg-Landau like potential and the scale parameter in the EW theory then become microscopic functions of the massive quark and antiquark fields, thus defining the matter-antimatter asymmetry and the dark matter content in the Universe at correct orders of magnitude. Thereby also the number of free parameters in the Standard Model is reduced. Key words: Quark Confinement; Matter-Antimatter Asymmetry, Dark Matter; Black Holes; New Vacuum; Baryogenesis; Inflation; WIMPs.   

Quantum Effects of Bose Dark Matter Structure Beyond the de Broglie Scale

Axions and axion-like particles are becoming increasingly attractive candidates for the dark matter. Likewise, searches for these candidates are increasing in sophistication, number, reach, and may span much of the candidates' viable parameter space in the next decade. Haloscope searches crucially depend on the form of the local axion halo distribution. However, our understanding of axion structure formation is far from complete, due largely to the candidate’s unique properties as a highly-degenerate Bose fluid. I present in this talk a novel model of structure formation for Bose dark matter that contains physically-motivated extra-classical physics above the de Broglie scale in the form of exchange-correlation interactions. Theory and preliminary N-body simulations show Bose correlations grow quickly in the early universe and that galaxies seeded by axion dark matter include unique extra-classical structures that may have observable consequences. Implications for dark matter axion searches such as the ADMX haloscope are also presented.   

Not Participating

Investigating the nature of dark energy in our universe is one of the main challenges of modern cosmology. This exotic source of stress-energy responsible for the late-time cosmic acceleration lacks a fundamental and well-defined theory. The simplest extension to the $\Lambda$CDM model is offered by dynamical dark energy models in which the late-time accelerated expansion is driven by an evolving scalar field, dubbed quintessence, undergoing motion on a fixed potential. Given their similarity in nature, there is a possibility that the energy density of the inflaton field that drove inflation has survived until late times to behave as quintessence. In this work, we describe a novel approach of unifying the two phases of accelerated expansions of the universe using a model that combines hilltop inflation with oscillating quintessence, while treating the reheating mechanism conventionally. The effects of the various models are analyzed using lattice simulations and tested against the 2018 Planck mission data. We show that a quintessential inflation model with a Coleman-Weinberg potential is consistent with the observed constraints and it allows for various cosmological predictions including the reheating temperature, and the mass and couplings of the inflaton field to be made.