We perform a systematic analysis of dark matter production during post-inflationary reheating. Following the period of exponential expansion, the inflaton begins a period of damped oscillations as it decays. These oscillations and the evolution of temperature of the thermalized decay products depend on the shape of the inflaton potential $V(Φ)$. We consider potentials of the form $Φ^k$. Standard matter-dominated oscillations occur for $k=2$. In general, the production of dark matter may depend on either (or both) the maximum temperature after inflation, or the reheating temperature, where the latter is defined when the Universe becomes radiation dominated. We show that dark matter production is sensitive to the inflaton potential and depends heavily on the maximum temperature when $k>2$. We also consider the production of dark matter with masses larger than the reheating temperature.
We analyse the epoch of reheating after an inflationary phase in the Randal Sundrum(RS) Type-$\rm II$ braneworld, where we did not consider any particular model of inflation, but rather reconstructed the inflationary potential solving the flow equations using Monte Carlo (MC) approach. It is shown numerically that a potential conceived through the MC reconstruction technique can be represented by an effective potential as a function of the number of e-foldings($N$). Then, the epoch of reheating is studied for this reconstructed potential. The relation between the reheating temperature ($T_{\rm…
We investigate the allowed range of reheating temperature values in light of the Planck 2015 results and the recent joint analysis of Cosmic Microwave Background (CMB) data from the BICEP2/Keck Array and Planck experiments, using monomial and binomial inflationary potentials. While the well studied $ϕ^2$ inflationary potential is no longer favored by current CMB data, as well as $ϕ^p$ with $p>2$, a $ϕ^1$ potential and canonical reheating ($w_{re}=0$) provide a good fit to the CMB measurements. In this last case, we find that the Planck 2015 $68\%$ confidence limit upper bound on the spectral i…
With the growing consensus on simple power law inflation models not being favored by the PLANCK observation, dynamics for the non-standard form of the inflaton potential gain significant interest in the recent past. In this paper, we analyze in great detail classes of phenomenologically motivated inflationary models with non-polynomial potential which are the generalization of the potential introduced in \cite{mhiggs}. After the end of inflation, inflaton field will coherently oscillate around its minimum. Depending upon the initial amplitude of the oscillation and coupling parameters standard…
We analyze in detail the perturbative decay of the inflaton oscillating about a generic form of its potential $V(ϕ) = ϕ^k$, taking into account the effects of non-instantaneous reheating. We show that evolution of the temperature as a function of the cosmological scale factor depends on the spin statistics of the final state decay products when $k > 2$. We also include the inflaton-induced mass of the final states leading to either kinematic suppression or enhancement if the final states are fermionic or bosonic respectively. We compute the maximum temperature reached after inflation, the subs…
We consider the generation of the baryon asymmetry in models with right-handed neutrinos produced through gravitational scattering of the inflaton during reheating. The right-handed neutrinos later decay and generate a lepton asymmetry, which is partially converted to a baryon asymmetry by Standard Model sphaleron processes. We find that a sufficient asymmetry can be generated for a wide range of right-handed neutrino masses and reheating temperatures. We also show that the same type of gravitational scattering produces Standard Model Higgs bosons, which can achieve inflationary reheating cons…
In non-oscillatory (NO) inflationary models, the reheating mechanism was usually based on gravitational particle production or the mechanism of instant preheating. In this paper we introduce the curvaton mechanism into NO models to reheat the universe and generate the curvature perturbation. Specifically we consider the Peebles-Vilenkin quintessential inflation model, where the reheating temperature can be extended from 1MeV to $10^{13}$GeV.
We discuss the possibility of explaining the recent NANOGrav results by inflationary gravitational waves (IGWs) with a blue-tilted primordial spectrum. Although such IGWs can account for the NANOGrav signal without contradicting the upper bound on the tensor-to-scalar ratio at the cosmic microwave background scale, the predicted spectrum is in strong tension with the upper bound on the amplitude of the stochastic gravitational wave background by big-bang nucleosynthesis (BBN) and the second LIGO-Virgo observation run. However, the thermal history of the Universe, such as reheating and late-tim…
It is well known that the inflationary scenario often displays different sets of degeneracies in its predictions for CMB observables. These degeneracies usually arise either because multiple inflationary models predict similar values for the scalar spectral index $n_{_S}$ and the tensor-to-scalar ratio $r$, or because within the same model, the values of $\lbrace n_{_S}, r \rbrace$ are insensitive to some of the model parameters, making it difficult for CMB observations alone to constitute a unique probe of inflationary cosmology. We demonstrate that by taking into account constraints on the p…
Thermal field theory is applied to particle production rates in inflationary models, leading to new results for catalysed, or two-stage decay, where massive fields act as decay channels for the production of light fields. A numerical investigation of the Bolztmann equation in an expanding universe shows that the particle distributions produced during small amplitude inflaton oscillations or alongside slowly moving inflaton fields can thermalise.
Reheating is an important part of inflationary cosmology. It describes the production of Standard Matter particles after the phase of accelerated expansion. We give a review of the reheating process, focusing on an in-depth discussion of the preheating stage which is characterized by exponential particle production due to a parametric resonance or tachyonic instability. We give a brief overview of the thermalization process after preheating and end with a survey of some applications to supersymmetric theories and to other issues in cosmology such as baryogenesis, dark matter and metric preheat…
We study slow roll single field inflationary scenario and the production of non-thermal fermionic dark matter, together with standard model Higgs, during reheating. For the inflationary scenario, we have considered two models of polynomial potential - one is symmetric about the origin and another one is not. We fix the coefficients of the potential from the current Cosmic Microwave Background (CMB) data from Planck/Bicep. Next, we explore the allowed parameter space on the coupling $(y_χ)$ with inflaton and mass $(m_χ)$ of dark matter (DM) particles $(χ)$ produced during reheating and satisfyi…
Reheating is the the epoch which connects inflation to the subsequent hot Big-Bang phase. Conceptually very important, this era is however observationally poorly known. We show that the current Planck satellite measurements of the Cosmic Microwave Background (CMB) anisotropies constrain the kinematic properties of the reheating era for most of the inflationary models. This result is obtained by deriving the marginalized posterior distributions of the reheating parameter for about 200 models taken in Encyclopaedia Inflationaris. Weighted by the statistical evidence of each model to explain the …
We exploit the complementarity among supersymmetry, inflation, axions, Big Bang Nucleosynthesis (BBN) and Cosmic Microwave Background Radiation (CMB) to constrain supersymmetric axion models in the light of the recent Planck and BICEP results. In particular, we derive BBN bounds coming from altering the light element abundances by taking into account hadronic and electromagnetic energy injection, and CMB constraints from black-body spectrum distortion. Lastly, we outline the viable versus excluded region of these supersymetric models that might account for the mild dark radiation observed.
We analyze the evolution of the perturbations in the inflaton field and metric following the end of inflation. We present accurate analytic approximations for the perturbations, showing that the coherent oscillations of the post-inflationary condensate necessarily break down long before any current phenomenological constraints require the universe to become radiation dominated. Further, the breakdown occurs on length-scales equivalent to the comoving post-inflationary horizon size. This work has implications for both the inflationary "matching" problem, and the possible generation of a stochas…
Among primordial magnetogenesis models, inflation is a prime candidate to explain the current existence of cosmological magnetic fields. Assuming conformal invariance to be restored after inflation, their energy density decreases as radiation during the decelerating eras of the universe, and in particular during reheating. Without making any assumptions on inflation, on the magnetogenesis mechanism and on how the reheating proceeded, we show that requiring large scale magnetic fields to remain subdominant after inflation gives non-trivial constraints on both the reheating equation of state par…
ACT DR6 Insights on the Inflationary Attractor models and Reheating
Tsung-Dao Lee Institute & School of Physics and Astronomy, Shanghai Jiao Tong University（上海交大李政道研究所与物理与天文学院）；Physics and Applied Mathematics Unit, Indian Statistical Institute（印度统计研究所物理与应用数学单元）
Recent blazar observations provide growing evidence for the presence of magnetic fields in the extragalactic regions. While a natural speculation is to associate the production to inflationary physics, it has been known that magnetogenesis solely from inflation is quite challenging. We therefore study a model in which a non-inflaton field $χ$ coupled to the electromagnetic field through its kinetic term, $-I^2(χ) F^2 /4$, continues to move after inflation until the completion of reheating. This leads to a post-inflationary amplification of the electromagnetic field. We compute all the relevant…
Inflationary reheating is almost completely controlled by the Floquet indices, $μ_k$. Using spectral theory we demonstrate that the stability bands (where $μ_k = 0$) of the Mathieu and Lamé equations are destroyed even in Minkowski spacetime, leaving a fractal Cantor set or a measure zero set of stable modes in the cases where the inflaton evolves in an almost-periodic or stochastic manner respectively. These two types of potential model the expected multi-field and quantum backreaction effects during reheating.
The low reheat temperature at the end of inflation from the gravitino bound constrains the creation of heavy Majorana neutrinos associated with models of leptogenesis. However, a detailed view of the reheating of the Universe at the end of inflation implies that the maximum temperature during reheating, $\Tmax$, can be orders of magnitude higher than the final reheat temperature. This then allows for the production of the heavy Majorana neutrinos needed for leptogenesis. We carry out the complementary calculation of the gravitino production during reheating and its dependence on $\Tmax$. We fi…
Gravitational scalar production with a generic reheating scenario
School of Theoretical Physics, Dublin Institute for Advanced Studies（都柏林高等研究院理论物理学院）；School of Physics, Faculty of Basic Sciences, University of Shanghai for Science and Technology（上海理工大学理学院物理系）
We present the first Bayesian constraints on the single field inflationary reheating era obtained from Cosmic Microwave Background (CMB) data. After demonstrating that this epoch can be fully characterized by the so-called reheating parameter, we show that it is constrained by the seven years Wilkinson Microwave Anisotropies Probe (WMAP7) data for all large and small field models. An interesting feature of our approach is that it yields lower bounds on the reheating temperature which can be combined with the upper bounds associated with gravitinos production. For large field models, we find th…
We consider $R^2$ inflation in the Palatini gravity assuming the existence of scalar fields, coupled to gravity in the most general manner. These theories, in the Einstein frame, and for one scalar field $h$, share common features with $K$ - inflation models. We apply this formalism for the study of popular inflationary models, whose potentials are monomials, $ V \sim h^{n} $, with $ n $ a positive even integer. We also study the Higgs model non-minimally coupled to gravity. Although these have been recently studied, in the framework of the Palatini approach, we show that the scalar power spec…
We consider the non-equilibrium evolution of the inflaton field coupled to both lighter scalars and fermions. The dissipational dynamics of this field is studied and found to be quite different than that believed in inflationary models. In particular, the damping time scale for the expectation value of the zero momentum mode of the inflaton can be much shorter than that given by the single particle decay rate when the inflaton amplitudes are large, as in chaotic inflation scenarios. We find that the reheating temperature may depart considerably from the usual estimates.
We explore a model of two-field inflation with nonminimal kinetic terms in which two identical matter sectors decoupled from each other may reheat to different temperatures while preserving the symmetry of the Lagrangian. This scenario is motivated by mirror dark matter models in which the temperature of the mirror sector is constrained to be $T'\lesssim0.5 T$ by big bang nucleosynthesis and the cosmic microwave background. For a given class of nonminimal kinematic terms, we find that the symmetric field trajectory $X=Y$ is a repeller solution, such that any randomly-occurring asymmetry in the…
We study a model for reheating that has been much investigated for parametric resonance, having a quartic interaction of the scalar inflaton with another scalar field. Attention is particularly on the quantum excitations of the inflaton field and the metric perturbation with a smooth transition from quantum to classical stochastic states, followed through from a specific inflation model to a state including a relativistic fluid. The scalar fields enter non-perturbatively but the metric enters perturbatively, and the validity of this latter is assessed. In this model our work seems to point the…
We study a minimal scenario to realize non-thermal leptogenesis and UV freeze-in of a Standard Model (SM) gauge singlet fermionic dark matter (DM) simultaneously, with inflaton field playing a non-trivial role in their yields. The renormalizable interactions are restricted to the SM fields, two right handed neutrinos (RHN) and inflaton coupling exclusively to the RHNs, while the DM couples to both the SM and the RHNs only via operators of dimension $d>4$. Considering two separate cases of $d=\{5,6\}$, we show that for $d=5$, inflaton decay into RHNs followed by their subsequent decay into SM p…
Recently we extended the standard model by four TeV-scale fields including a singlet fermion, an isotriplet and two isosinglet diquark scalars to generate the cosmological baryon asymmetry with an observable neutron-antineutron oscillation. We now supersymmetrize our model but do not constrain it at the TeV scale. The superpartner of the singlet fermion can serve as an inflaton field. Its three-body decays, mediated by the isosinglet diquarks and their superpartners, can simultaneously provide a low reheating temperature and a sizable CP asymmetry. We thus can realize a nonthermal baryogenesis…
We numerically investigate the decay, via parametric resonance, of the inflaton with an m^2 phi^2 potential into a scalar matter field with a symmetry breaking potential. We consider the case where symmetry breaking takes place during inflation. We show that when expansion is not taken into account symmetry restoration and non-thermal defect production during reheating is possible. However in an expanding universe the fields do not spend sufficient time in the instability bands; thus symmetry restoration and subsequent domain wall production do not occur.
Dark matter may only interact with the visible sector efficiently at energy scales above the inflaton mass, such as the Planck scale or the grand unification scale. In such a scenario, the dark matter is mainly produced out of equilibrium during the period of reheating, often referred to as UV freeze-in. We evaluate the abundance of the dark matter generated from bremsstrahlung off the inflaton decay products assuming no direct coupling between the inflaton and the dark matter. This process generally dominates the production of dark matter for low reheating temperatures where the production th…
Grand unified theories may display multiply interacting fields with strong coupling dynamics. This poses two new problems: (1) What is the nature of chaotic reheating after inflation, and (2) How is reheating sensitive to the mass spectrum of these theories ? We answer these questions in two interesting limiting cases and demonstrate an increased efficiency of reheating which strongly enhances non-thermal topological defect formation, including monopoles and domain walls. Nevertheless, the large fluctuations may resolve this monopole problem via a modified Dvali-Liu-Vachaspati mechanism in whi…
In this paper we study the reheating constraints on inflationary models considering perturbatively decaying inflaton. Important difference with the existing analysis is the inclusion of explicit decaying dynamics of inflaton during reheating. One of the important findings of our analysis is the possible existence of maximum reheating temperature $T_{re}^{max}$ considering perturbative reheating scenario. For all the models under consideration the value of this temperature turned out to be $T_{re}^{max} \sim 10^{15}$ GeV. Corresponding to this value of reheating temperature the duration of rehe…
We study the potential impact of detecting the inflationary gravitational wave background by the future space-based gravitational wave detectors, such as DECIGO and BBO. The signal-to-noise ratio of each experiment is calculated for chaotic/natural/hybrid inflation models by using the precise predictions of the gravitational wave spectrum based on numerical calculations. We investigate the dependence of each inflation model on the reheating temperature which influences the amplitude and shape of the spectrum, and find that the gravitational waves could be detected for chaotic/natural inflation…
Models of leptogenesis are constrained by the low reheat temperature at the end of reheating associated with the gravitino bound. However a detailed view of reheating, in which the maximum temperature during reheating, $\Tmax$, can be orders of magnitude higher than the reheat temperature, allows for the production of heavy Majorana neutrinos needed for leptogenesis. But then one must also consider the possibility of enhanced gravitino production in such scenarios. In this article we consider gravitino production during reheating, its dependence on $\Tmax$, and its relevance for leptogenesis. …
Recent progress in the preheating phenomena for inflationary cosmology is reviewed. We first discuss estimates of the preheating time scale and particle production at the early stages of parametric amplification within the Mathieu and Lam'e approximations and we analyze their precision and limitations. The necessity of self-consistent calculations including the non-linearity of the field theory equations in an energy conserving scheme is stressed. The large N calculations including the field back-reaction are reviewed. For spontaneously broken theories the issue of symmetry restoration is anal…
As additional perturbative degrees of freedom, it is known that magnetic fields of inflationary origin can source curvature perturbations on super-Hubble scales. By requiring the magnetic generated curvature to remain smaller than its inflationary adiabatic counterpart during inflation and reheating, we derive new constraints on the maximal field value today, the reheating energy scale and its equation of state parameter. These bounds end up being stronger by a few order of magnitude than those associated with a possible backreaction of the magnetic field onto the background. Our results are r…
We consider the CMB constraints on reheating and dark matter parameter space for a specific plateau type inflationary model. The plateau inflationary models which are currently most favored models from data can be well approximated by a potential of the form $V(ϕ)\propto ϕ^n$ around $ϕ=0$. This fact makes it possible to study the reheating phase with general inflaton equation of state in a viable cosmological scenario. In addition, following our recent work[1], we generalize the connection between reheating and the present CMB data and the dark matter parameter space for general inflaton equat…
In this paper, we studied the phenomenological consequences of recently proposed swampland conjecture on the inflationary models though constraints on reheating. If dark matter is assumed to be produced during reheating, the conjecture will provide further constraints on the dark matter parameter space through its current relic abundance. As has been pointed out already and also analyzed in our present paper any successful inflationary scenario is in clear tension with the aforementioned conjecture in its current form. However considering the swampland parameters to be free and constrained by …
A kinetic mixing between the axion and the inflaton allows for a production of axion dark matter even if the inflationary Hubble scale is smaller than the zero-temperature axion mass. We analyze the axion dynamics in this recently discovered "inflaxion" framework, and present a new cosmological scenario where the axion drifts away from its vacuum during the reheating epoch, giving rise to the observed dark matter abundance. We discuss the implications for both the QCD axion and axion-like particles.
We characterize the post-inflationary dynamics of an inflaton $ϕ$ coupled to multiple interacting daughter fields $X_n$ ($n=1,\dots N_d$) through quadratic-quadratic interactions $g_n^ 2ϕ^2 X_n^2$. We assume a monomial inflaton potential $V(ϕ) \propto |ϕ|^p$ ($p \geq 2$) around the minimum. By simulating the system in 2+1-dimensional lattices, we study the post-inflationary evolution of the energy distribution and equation of state, from the end of inflation until a stationary regime is achieved. We show that in this scenario, the energy transferred to the daughter field sector can be larger t…
The existence of a shadow world (or mirror universe) with matter and forces identical to that of the visible world but interacting with the latter only via gravity can be motivated by superstring theories as well as by recent attempts to understand the nature of a sterile neutrino needed if all known neutrino data are to be consistent with each other. A simple way to reconcile the constraints of big bang nucleosynthesis in such a theory is to postulate that the reheating temperature after inflation in the mirror universe is lower than that in the visible one. We have constructed explicit model…
Coherent oscillations of the inflaton field at the end of inflation can parametrically excite fermions in much the same way that bosons are created in preheating. Although Pauli-blocking prohibits the occupation number of created fermions from growing exponentially, fermion production occurs in a manner significantly different from the expectations of simple perturbation theory. Here, I discuss the nature of fermion production after inflation and possible applications including the efficient transfer of inflaton energy and the production of super-massive fermions during fermionic preheating.
Evidence from the BICEP2 experiment for a significant gravitational-wave background has focussed attention on inflaton potentials $V(ϕ) \propto ϕ^α$ with $α=2$ ("chaotic" or "$m^2ϕ^2$" inflation) or with smaller values of $α$, as may arise in axion-monodromy models. Here we show that reheating considerations may provide additional constraints to these models. The reheating phase preceding the radiation era is modeled by an effective equation-of-state parameter $w_{\rm re}$. The canonical reheating scenario is then described by $w_{\rm re}=0$. The simplest $α=2$ models are consistent with $w_{\…
