Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userChiral Tensor Particles in the Early Universe - Present Status
114
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
In this work an update of the cosmological role and place of the chiral tensor particles in the Universe history is provided. We discuss an extended model with chiral tensor particles. The influence of these particles on the early Universe evolution is studied. Namely, the increase of the Universe expansion rate caused by the additional particles in this extended model is calculated, their characteristic interactions with the particles of the hot Universe plasma are studied and the corresponding times of their creation, scattering, annihilation and decay are estimated for accepted values of their masses and couplings, based on the recent experimental constraints. The period of abundant presence of these particles in the Universe evolution is determined.
rate research
Read More
Chiral dynamo converting asymmetry between right and left-handed leptons in the early universe into helical magnetic field has been proposed as a possible cosmological magnetogenesis scenario. We show that this mechanism is strongly affected by viscous damping of primordial plasma motions excited by the dynamo. This effect modifies the expected range of strength and correlation length of the chiral dynamo field which could have survived till present epoch in the voids of the Large Scale Structure. We show the range of parameters of chiral dynamo field that may have survived in the voids is still consistent with existing lower bounds on intergalactic magnetic field from gamma-ray observations, but only if the right-left lepton asymmetry at the temperature T~80 TeV is very high, close to the maximal possible value.
The evolution of the Universe is the ultimate laboratory to study fundamental physics across energy scales that span about 25 orders of magnitude: from the grand unification scale through particle and nuclear physics scales down to the scale of atomic physics. The standard models of cosmology and particle physics provide the basic understanding of the early and present Universe and predict a series of phase transitions that occurred in succession during the expansion and cooling history of the Universe. We survey these phase transitions, highlighting the equilibrium and non-equilibrium effects as well as their observational and cosmological consequences. We discuss the current theoretical and experimental programs to study phase transitions in QCD and nuclear matter in accelerators along with the new results on novel states of matter as well as on multi- fragmentation in nuclear matter. A critical assessment of similarities and differences between the conditions in the early universe and those in ultra- relativistic heavy ion collisions is presented. Cosmological observations and accelerator experiments are converging towards an unprecedented understanding of the early and present Universe.
The early stages of the universe evolution are discussed according to the hot big bang model and the grand unified theories. The shortcomings of big bang are summarized and their resolution by inflationary cosmology is sketched. Cosmological inflation, the subsequent oscillation and decay of the inflaton field, and the resulting reheating of the universe are studied in some detail. The density perturbations produced by inflation and the temperature fluctuations of the cosmic microwave background radiation are introduced. Baryogenesis via non-thermal leptogenesis is analyzed and dark energy and matter in the universe are presented. Quantum gravity and string theory are very briefly introduced. The problem of initial conditions for inflation is discussed in the light of string theory and the possibly detectable primordial gravity waves from inflation are mentioned.
The cosmological evolution can modify the dark matter (DM) properties in the early Universe to be vastly different from the properties today. Therefore, the relation between the relic abundance and the DM constraints today needs to be revisited. We propose novel textit{transient} annihilations of DM which helps to alleviate the pressure from DM null detection results. As a concrete example, we consider the vector portal DM and focus on the mass evolution of the dark photon. When the Universe cools down, the gauge boson mass can increase monotonically and go across several important thresholds; opening new transient annihilation channels in the early Universe. Those channels are either forbidden or weakened at the late Universe which helps to evade the indirect searches. In particular, the transient resonant channel can survive direct detection (DD) without tuning the DM to be half of the dark photon mass and can be soon tested by future DD or collider experiments. A feature of the scenario is the existence of a light dark scalar.
Electron-positron annihilation largely occurs in local thermal and chemical equilibrium after the neutrinos fall out of thermal equilibrium and during the Big Bang Nucleosynthesis (BBN) epoch. The effects of this process are evident in BBN yields as well as the relativistic degrees of freedom. We self-consistently calculate the collision integral for electron-positron creation and annihilation using the Klein-Nishina amplitude and appropriate statistical factors for Fermi-blocking and Bose-enhancement. Our calculations suggest that this annihilation freezes out when the photon-electron-positron-baryon plasma temperature is approximately 16 keV, after which its rate drops below the Hubble rate. In the temperature regime near 16 keV, we break the assumption of chemical equilibrium between the electrons, positrons, and photons to independently calculate the evolution of the chemical potentials of the electrons and positrons while computing the associated collision integrals at every time step. We find that the electron and positron chemical potentials deviate from the case with chemical equilibrium. While our results do not affect the interpretation of precision cosmological measurements in elucidating the standard cosmological model, these out of equilibrium effects may be important for testing physics beyond the standard model.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
