We consider the generic injection of radiation (both dark and electromagnetic) during the epoch between big bang nucleosynthesis (BBN) and recombination. The contribution of the additional radiation to the number of effective neutrinos may be quite small in this scenario, since dark radiation and electromagnetic radiation provide contributions of opposite sign. However, the injection of electromagnetic radiation dilutes the baryon-to-entropy ratio, which is measured both at BBN and at recombination. As a result, this scenario is expected to be tightly constrained. Indeed, performing a numerical study, we find that the allowed amount of extra radiation may be no more than $\sim 25\%$ greater than in the case where it is assumed to be entirely dark radiation.
Updated BBN Bounds on Hadronic Injection in the Early Universe: The Gravitino Problem
Universidade Federal do Rio Grande do Norte（北里奥格兰德联邦大学）；International Institute of Physics, Universidade Federal do Rio Grande do Norte（北里奥格兰德联邦大学国际物理研究所）；Millennium Institute for Subatomic Physics at the High-Energy Frontier (SAPHIR) of ANID（智利国家研究与创新发展局高能前沿亚原子物理学千年研究所）；Universita degli Studi di Messina（墨西拿大学）；INFN Sezione di Catania（意大利国家核物理研究所卡塔尼亚分部）；Universidad de La Serena（拉塞雷纳大学）
We reconsider the effective mass of a scalar field which interact with visible sector via Planck-suppressed coupling in supergravity framework. We focus on the radiation-dominated (RD) era after inflation. In this era, the effective mass is given by thermal average of interaction terms. To make our analysis clear, we rely on Kadanoff-Baym equations to evaluate the thermal average. We find that, in RD era, a scalar field acquires the effective mass of the order of $H$.
The cosmological constant is not necessarily small in the early universe. If a scalar field obtains a vacuum expectation value after a phase transition (PT), a possibly large cosmological constant could present before PT. The early cosmological constant (ECC) and the PT process may be detectable from dark radiation (DR) today, such as in the cosmic axion background. We show that for a broad class of DR models, the DR density and spectrum are significantly modified by the presence of an ECC. From the density and the spectrum of the DR today, we can deduce the temperature and the strength of the…
The characteristic distribution of the matter in the universe and its observable expansion with apparent acceleration is the result of historical event - massive stellar explosions' radiation pressure on drifting particles of hydrogen environment in the early stage of universe evolution.
We devise a new user-friendly tool interfaced with the Boltzmann code CLASS to deal with any kind of exotic electromagnetic energy injection in the universe and its impact on anisotropies of the Cosmic Microwave Background. It makes use of the results from standard electromagnetic cascade calculations develop in the context of WIMP annihilation, generalized to incorporate any injection history. We first validate it on a specific WIMP scenario, the Higgs Portal model, confirming that the standard effective on-the-spot treatment is accurate enough. We then analyze the more involved example of ev…
High energy neutrinos and anti-neutrinos ($\gtrsim$ 100 GeV) can inject energetic electromagnetic particles into the baryon-photon plasma in the high redshift universe through electroweak showers from electroweak bremsstrahlung, inelastic scattering with the background electrons and nucleons, and by pair-production of standard model particles on background neutrinos and anti-neutrinos. In this paper, we evolve the particle cascades of high energy non-thermal neutrinos injections, using dark matter decay as a specific example, including relevant collision processes of these neutrinos with the b…
Spectral distortions (SDs) of the cosmic microwave background (CMB) provide a powerful tool for studying particle physics. Here we compute the distortion signals from decaying particles that convert directly into photons at different epochs during cosmic history, focusing on injection energies $E_\mathrm{inj}\lesssim 20\,\mathrm{keV}$. We deliver a comprehensive library of SD solutions that can be used to study a wide range of particle physics scenarios. We use {\tt CosmoTherm} to compute the SD signals, including effects on the ionization history and opacities of the Universe. We also conside…
If even a relatively small number of black holes were created in the early universe, they will constitute an increasingly large fraction of the total energy density as space expands. It is thus well-motivated to consider scenarios in which the early universe included an era in which primordial black holes dominated the total energy density. Within this context, we consider Hawking radiation as a mechanism to produce both dark radiation and dark matter. If the early universe included a black hole dominated era, we find that Hawking radiation will produce dark radiation at a level $ΔN_{\rm eff} …
Axions seem ubiquitous in string theories and some of them may be produced non-thermally by heavy scalar decays, contributing to dark radiation. We study various cosmological effects of photons produced from the axionic dark radiation through axion-photon conversion in the presence of primordial magnetic fields, and derive tight constraints on the combination of the axion-photon coupling and the primordial magnetic field.
Recent cosmological observations, such as the measurement of the primordial 4He abundance, CMB, and large scale structure, give preference to the existence of extra radiation component, Delta N_nu > 0. The extra radiation may be accounted for by particles which were in thermal equilibrium and decoupled before the big bang nucleosynthesis. Broadly speaking, there are two possibilities: 1) there are about 10 particles which have very weak couplings to the standard model particles and decoupled much before the QCD phase transition; 2) there is one or a few light particles with a reasonably strong…
The universe has evolved through several phases as its various constituents dominated its energy content. Candidate dark matter particles may have undergone freeze-out during any such phase. While the standard freeze-out scenarios have been explored during the radiation-dominated era, and more recently during scalar field decay, this work extends the study of dark matter freeze-out to a potential early period during which the universe is matter-dominated and its evolution adiabatic. Decoupling during an adiabatic matter dominated era changes the freeze-out dynamics, since the Hubble rate is pa…
We present a novel mechanism for the present acceleration of the universe. We find that the temperature of the Unruh radiation perceived by the brane is not equal to the inherent temperature (Hawking temperature at the apparent horizon) of the brane universe in the frame of Dvali-Gabadadze-Porrati (DGP) braneworld model. The Unruh radiation perceived by a dust dominated brane is always warmer than the brane measured by the geometric temperature, which naturally induces an energy flow between bulk and brane based on the most sound thermodynamics principles. Through a thorough investigation to t…
A scheme for incorporating the creation of radiation and matter into the cosmological evolution is introduced so that it becomes possible to merge the times before and after the creation of radiation and matter in a single scale factor in Robertson-Walker metric. This scheme is illustrated through a toy model that has the prospect of constituting a basis for a realistic model.
The present article discusses about the effect of a Lee-Wick partner infested radiation phase of the early universe. As Lee-Wick partners can contribute negative energy density so it is always possible that at some early phase of the universe when the Lee-Wick partners were thermalized the total energy density of the universe became very small making the effective Hubble radius very big. This possibility gives rise to the probability of a bouncing universe. As will be shown in the article that a simple Lee-Wick radiation is not enough to produce a bounce. There can be two possibilities which c…
The relationship between the cosmic microwave background radiation temperature and the redshift, i.e., the $T$--$z$ relation, is examined in a phenomenological dissipative model. The model contains two constant terms, as if a nonzero cosmological constant $Λ$ and a dissipative process are operative in a homogeneous, isotropic, and spatially flat universe. The $T$--$z$ relation is derived from a general radiative temperature law, as appropriate for describing nonequilibrium states in a creation of cold dark matter (CCDM) model. Using this relation, the radiation temperature in the late universe…
Spectral distortions and anisotropies of the CMB provide independent and complementary probes to study energy injection processes in the early universe. Here we discuss the synergy between these observables, and show the promising future of spectral distortion missions to constrain both exotic and non-exotic energy injections. We show that conventional probes such as Big Bang Nucleosynthesis and CMB anisotropies can benefit from and even be surpassed by future spectral distortion experiments. For this, we have implemented a unified framework within the Boltzmann code CLASS to consistently trea…
Constraining primordial non-Gaussianity and energy injection with the thermal Sunyaev-Zeldovich effect and integrated Sachs-Wolfe effect cross-correlation
Guangdong Technion - Israel Institute of Technology（广东以色列理工学院）；North-West University（西北大学）；Adekunle Ajasin University（阿德库恩莱·阿贾辛大学）；Stellenbosch University（斯泰伦博斯大学）；National Institute for Theoretical and Computational Sciences (NITheCS)（南非国家理论与计算科学研究所）
Kinetic equations for ultrarelativistic particles with due account of gravitational interactions with massive particles in the Robertson-Walker universe are obtained. On the basis of an exact solution of the kinetic equations thus obtained, a conclusion is made as to the high degree of the uniformity of the relict radiation on scales with are less than $10'$.
It is well known that there is a Hawking radiation from the cosmological horizon of the de-sitter spacetime, and the de-sitter spacetime can be a special case of a FRW universe. Therefore, there may be a corresponding Hawking radiation in a FRW universe. Indeed, there have been several clues showing that there is a Hawking radiation from the apparent horizon of a FRW universe. In our paper, however, we find that the Hawking radiation may come from the cosmological horizon. Moreover, we also find that the Hawking radiation from the apparent horizon of a FRW universe in some previous works can b…
Gravitational waves (GWs) are produced by colliding particles through the gravitational analogue of electromagnetic bremsstrahlung. We calculate the contribution of free-free emission in the radiation-dominated Universe to the stochastic GW background. We find that the energy density of the resulting GW radiation is heavily dependent on the number of elementary particles, $N_{\mathrm{tot}}$, and the maximum initial temperature, $T_{\mathrm{max}}$. We rule out $N_{\mathrm{tot}}\gtrsim N_{\mathrm{SM}}$ for $T_{\mathrm{max}}\sim T_{\mathrm{Planck}}\approx10^{19}$ GeV and $N_{\mathrm{tot}}\gtrsim1…
We construct the effective field theory of a perfect fluid in the early universe. Focusing on the case where the fluid has the equation of state of radiation, we show that it may lead to corrections to the background dynamics that can dominate over those of an effective field theory of gravity alone. We describe the periods of accelerated expansion, in the form of inflationary and bounce solutions, that arise in the background dynamics and discuss their regime of validity within EFT.
We discuss the generalized second law (GSL) and the constraints imposed by it for two types of Friedmann universes. The first one is the Friedmann universe with radiation and a positive cosmological constant, and the second one consists of non-relativistic matter and a positive cosmological constant. The time evolution of the event horizon entropy and the entropy of the contents within the horizon are analyses in an analytical way by obtaining the Hubble parameter. It is shown that the GSL constraint the temperature of both the radiation and matter of the Friedmann universe. It is also shown t…
We study a black hole in an expanding Universe during the radiation-dominated stage. In the case when the black hole radius is much smaller than the cosmological horizon, we present a solution of the Einstein equations for the metric, the matter density and velocity distributions. At distances much smaller than the cosmological horizon the solution features quasi-stationary accretion, while at large distances the solution asymptotes the homogeneous radiation dominated FLRW. We discuss how our solution is related to the McVittie solution. The obtained results can be applied, in particular, for …
The classical Friedmann-Lemaître equations are solved using a corrected version of Planck's radiation law. The function curves of the scale parameter a(t) and the variations with temperature a(T) and t(T) are given. It is shown that a reasonable cosmological evolution is only possible in case of flat spatial slices (k=0). The initial singularity is avoided. Horizon and flatness problems do not exist. For low temperatures compared with the Planck Temperatur, the equations yield the usual course of expansion of the standard FLRW model for a radiation universe with k=0 and p=u(T)/3.
Within the framework of a flat cosmological model a propagation of an instantaneous burst of nonpolarized isotropic radiation is considered from the moment of its beginning at some initial redshift z0 to the moment of its registration now (at z=0). Thomson (Rayleigh) scattering by free electrons is considered as the only source of opacity. Spatial distributions of the mean (over directions) radiation intensity are calculated as well as angular distributions of radiation intensity and polarization at some different distances from the center of the burst. It is shown that for redshifts z0 large …
In this work we derive a scenario {in which} the early universe consists of {radiation fluid} and Bose-Einstein condensate. The possibility of gravitational self-interaction due to an attractive Bose-Einstein condensate is analyzed. The classical behavior of the scale factor of the universe is determined by a parameter associated with the Bose-Einstein fluid with bouncing or Big Crunch solutions. After we proceed to compute the finite-norm wave packet solutions to the Wheeler-DeWitt equation. The behavior of the scale factor is studied by applying the many-worlds interpretation of quantum mech…
We provide evidence that gravitational radiation in a 4D radiation-dominated universe, with equation-of-state $w=1/3$, consists of two components: helicity-2 gravitons and massless scalar acoustic waves. On physical grounds, we would expect the homogeneous solution of the Weyl tensor components to be a good approximation to its inhomogeneous counterparts, whenever the observer is located well in the far zone of an isolated astrophysical source of cosmological gravitational radiation. We show explicitly that these homogeneous and inhomogeneous solutions both receive contributions from the gauge…
We draw attention to observational evidence indicating that a substantial fraction of the well-known cosmic celestial diffuse ultraviolet background radiation field is actually due not to dust-scattered starlight, but rather---considering its spectral character at most locations in the sky---has an unknown physical origin. We arrive at this conclusion from re-examination of spectra of the diffuse ultraviolet background that were obtained---long ago---using the ultraviolet spectrometers aboard the two Voyager spacecraft, which were located far out in our solar system, and at very different loca…
We consider General Relativity with matter, radiation and a minimally coupled dark energy defined by an equation of state w. Using dynamical system method, we find the equilibrium points of such a theory assuming an expanding Universe and a positive dark energy density. Two of these points correspond to classical radiation and matter dominated epochs for the Universe. For the other points, dark energy mimics matter, radiation or accelerates Universe expansion. We then look for possible sequences of epochs describing a Universe starting with some radiation dominated epoch(s) (mimicked or not by…
It is commonly assumed that the energy density of the Universe was dominated by radiation between reheating after inflation and the onset of matter domination 54,000 years later. While the abundance of light elements indicates that the Universe was radiation dominated during Big Bang Nucleosynthesis (BBN), there is scant evidence that the Universe was radiation dominated prior to BBN. It is therefore possible that the cosmological history was more complicated, with deviations from the standard radiation domination during the earliest epochs. Indeed, several interesting proposals regarding vari…
In this work the homogeneous and isotropic Universe of Friedmann-Robertson-Walker is studied in the presence of two fluids: stiff matter and radiation described by the Schutz's formalism. We obtain to the classic case the behaviour of the scale factor of the universe. For the quantum case the wave packets are constructed and the wave function of the universe is found.
The Friedman-Robertson-Walker (FRW) space-time exhibits particle creation similar to Hawking radiation of a black hole. In this essay we show that this FRW Hawking radiation leads to an effective negative pressure fluid which can drive an inflationary period of exponential expansion in the early Universe. Since the Hawking temperature of the FRW space-time decreases as the Universe expands this mechanism naturally turns off and the inflationary stage transitions to a power law expansion associated with an ordinary radiation dominated Universe.
A massive primordial halo near an intensely star-forming galaxy may collapse into a supermassive star (SMS) and leave a massive black hole seed of about $10^5~M_{\odot}$. To investigate the impact of ionizing radiation on the formation of an SMS from a nearby galaxy, we perform three-dimensional radiation hydrodynamical simulations by selecting a pair of massive dark matter halos forming at $z >10$. We find that rich structures such as clumps and filaments around the source galaxy shield the cloud from ionizing radiation. In fact, in some cases, cloud collapse is accelerated under ionizing rad…
We investigate the creation of dark matter particles as a result of the decay of the scalar field in the framework of warm inflationary models, by using the irreversible thermodynamics of open systems with matter creation/annihilation. We consider the scalar fields, radiation and dark matter as an interacting three component cosmological fluid in a homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe, in the presence of the curvature terms. The thermodynamics of open systems as applied together with the gravitational field equations to the three component cosmological …
The evolution of the perturbations in the energy density and the particle number density in a flat Friedmann-Lemaitre-Robertson-Walker universe in the radiation-dominated era and in the epoch after decoupling of matter and radiation is studied. For large-scale perturbations the outcome is in accordance with treatments in the literature. For small-scale perturbations the differences are conspicuous. Firstly, in the radiation-dominated era small-scale perturbations grew proportional to the square root of time. Secondly, perturbations in the Cold Dark Matter particle number density were, due to g…
