Search

We consider a dark confining gauge theory with millicharged ultralight pions (ULP) and heavy baryons as dark matter candidates. The model simultaneously realizes the ultralight (strongly interacting ultralight millicharged particle or “STUMP”) and superheavy (“WIMPzilla”) dark matter paradigms, connected by the confinement scale of the dark QCD. It is a realization of millicharged ultralight dark matter, unlike conventional axions, and exhibits a mass splitting between the charged and neutral pions. ULPs can easily provide the observed density of the dark matter, and be cosmologically stable, for a broad range of dark QCD scales and quark masses. The dark baryons, produced via gravitational particle production or via freeze-in, provide an additional contribution to the dark matter density. Dark matter halos and boson stars in this context are generically an admixture of the three pions and heavy baryons, leading to a diversity of density profiles. That opens up the accessible parameter space of the model compared with the standard millicharged dark matter scenarios and can be probed by future experiments. We briefly discuss additional interesting phenomenology, such as ULP electrodynamics, and cosmic ULP backgrounds. We consider a dark confining gauge theory with millicharged Ultra-Light Pions (ULP) and heavy baryons as dark matter candidates. The model simultaneously realizes the ultra-light (STrongly-interacting Ultralight Millicharged Particle or "STUMP") and superheavy ("WIMPzilla") dark matter paradigms, connected by the confinement scale of the dark QCD. It is a realization of millicharged ULDM, very unlike conventional axions, and exhibits a mass splitting between the charged and neutral pions. ULPs can easily provide the observed density of the dark matter, and be cosmologically stable, for a broad range of dark QCD scales and quark masses. The dark baryons, produced via gravitational particle production or via freeze-in, provide an additional contribution to the dark matter density. Dark matter halos and boson stars in this context are generically an admixture of the three pions and heavy baryons, leading to a diversity of density profiles. That opens up the accessible parameter space of the model compared with the standard millicharged DM scenarios and can be probed by future experiments. We briefly discuss additional interesting phenomenology, such as ULP electrodynamics, and Cosmic ULP Backgrounds.

We introduce an axion-inflation model embedded in the left-right symmetric extension of the Standard Model in which ${W}_{R}$ is coupled to the axion. This model merges three milestones of modern cosmology, i.e., inflation, cold dark matter, and baryon asymmetry. Thus, it can naturally explain the observed coincidences among cosmological parameters, i.e., ${\ensuremath{\eta}}_{\mathsf{B}}\ensuremath{\approx}{P}_{\ensuremath{\zeta}}$ and ${\mathrm{\ensuremath{\Omega}}}_{\mathrm{DM}}\ensuremath{\simeq}5{\mathrm{\ensuremath{\Omega}}}_{\mathsf{B}}$. The source of asymmetry is spontaneous $CP$ violation in the physics of inflation, and the lightest right-handed neutrino is the cold dark matter candidate with mass ${m}_{{N}_{1}}\ensuremath{\sim}1\text{ }\text{ }\mathrm{GeV}$. The introduced mechanism does not rely on the largeness of the unconstrained $CP$-violating phases in the neutrino sector or fine-tuned masses for the heaviest right-handed neutrinos. It has two unknown fundamental scales, i.e., scale of inflation ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{inf}}=\sqrt{H{M}_{\mathrm{Pl}}}$ and left-right symmetry breaking ${\mathrm{\ensuremath{\Lambda}}}_{F}$. Sufficient matter asymmetry demands that ${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{inf}}\ensuremath{\approx}{\mathrm{\ensuremath{\Lambda}}}_{F}$. Baryon asymmetry and dark matter today are remnants of a pure quantum effect (chiral anomaly) in inflation, which, thanks to flavor effects, has been memorized by cosmic evolution.

Non-Abelian gauge fields may exist during inflation. We study the Schwinger effect by an $SU(2)$ gauge field coupled to a charged scalar doublet in a (quasi) de Sitter background and the possible backreaction of the generated charged particles on the homogeneous dynamics. Contrary to the Abelian $U(1)$ case, we find that both the Schwinger pair production and the induced current decrease as the interaction strength increases. The reason for this suppression is the isotropic vacuum expectation value of the $SU(2)$ field which generates a (three times) greater effective mass for the scalar field than the $U(1)$. In the weak interaction limit, the above effect is negligible and both the $SU(2)$ and $U(1)$ cases exhibit a linear increase of the current and a constant conductivity with the interaction strength. We conclude that the Schwinger effect does not pose a threat to the dynamics of inflationary models involving an $SU(2)$ gauge field., Comment: Minor changes

SU(2) gauge fields coupled to an axion field can acquire an isotropic background solution during inflation. We study homogeneous but anisotropic inflationary solutions in the presence of such (massless) gauge fields. A gauge field in the cosmological background may pose a threat to spatial isotropy. We show, however, that such models $\textit{generally}$ isotropize in Bianchi type-I geometry, and the isotropic solution is the attractor. Restricting the setup by adding an axial symmetry, we revisited the numerical analysis presented in Wolfson et.al (2020). We find that the reported numerical breakdown in the previous analysis is an artifact of parametrization singularity. We use a new parametrization that is well-defined all over the phase space. We show that the system respects the cosmic no-hair conjecture and the anisotropies always dilute away within a few e-folds., 23 pages, 14 figures. Published 23 September 2021 Updated to published version

Upon embedding the axion-inflation in the minimal left-right symmetric gauge extension of the SM with gauge group $SU(2)_L\times SU(2)_R \times U(1)_{B-L}$, [arXiv:2012.11516] proposed a new particle physics model for inflation. In this work, we present a more detailed analysis. As a compelling consequence, this setup provides a new mechanism for simultaneous baryogenesis and right-handed neutrino creation by the chiral anomaly of $W_R$ in inflation. The lightest right-handed neutrino is the dark matter candidate. This setup has two unknown fundamental scales, i.e., the scale of inflation and left-right symmetry breaking $SU(2)_R\times U(1)_{B-L}\rightarrow U(1)_{Y}$. Sufficient matter creation demands the left-right symmetry breaking scale happens shortly after the end of inflation. Interestingly, it prefers left-right symmetry breaking scales above $10^{10}~GeV$, which is in the range suggested by the non-supersymmetric SO(10) Grand Unified Theory with an intermediate left-right symmetry scale. Although $W_R$ gauge field generates equal amounts of right-handed baryons and leptons in inflation, i.e. $B-L=0$, in the Standard Model sub-sector $B-L_{SM}\neq 0$. A key aspect of this setup is that $SU(2)_R$ sphalerons are never in equilibrium, and the primordial $B-L_{SM}$ is conserved by the Standard Model interactions. This setup yields a deep connection between CP violation in physics of inflation and matter creation (visible and dark); hence it can naturally explain the observed coincidences among cosmological parameters, i.e., $\eta_{B}\simeq 0.3 P_{\zeta}$ and $\Omega_{DM}\simeq 5\Omega_{B}$. The $SU(2)_R$-axion inflation comes with a cosmological smoking gun; chiral, non-Gaussian, and blue-tilted gravitational wave background, which can be probed by future CMB missions and laser interferometer detectors., Comment: 28+20 Pages, 15 Figs

$SU(2)$ gauge fields and axions can have a stable, isotropic and homogeneous configuration during inflation. However, couplings to other matter species lead to particle production, which in turn induces backreaction on and destabilization of the non-Abelian and axion background. In this paper, we first study the particle production by a $SU(2)$ gauge field coupled to a massive Dirac doublet. To carry out this calculation we have made two technical improvements compared to what has been done in the literature. First, we apply the antisymmetrization of the operators to treat particles and antiparticles on equal footing; second, to deal with the UV divergences, we apply instantaneous subtraction. We find that the backreaction of produced fermions on the $SU(2)$ background is negligible for model parameters of observational interest. Next, we consider production of fermions due to coupling to the axion. The tree-level backreaction on the gauge fields, as well as on the axion, is vanishingly small. We also provide an estimate for the loop effects.

The key to the phenomenological success of inflation models with axion and SU(2) gauge fields is the isotropic background of the SU(2) field. Previous studies showed that this isotropic background is an attractor solution during inflation starting from anisotropic (Bianchi Type I) spacetime; however, not all possible initial anisotropic parameter space was explored. In this paper, we explore more generic initial conditions without assuming the initial slow-roll dynamics. We find some initial anisotropic parameter space which does not lead to the isotropic background, but to violation of slow-roll conditions, terminating inflation prematurely. The basin of attraction increases when we introduce another scalar field acting as inflaton and make the axion-SU(2) system a spectator sector. Therefore, the spectator axion-SU(2) model is phenomenologically more attractive., Comment: 22 pages, 9 figures. Updated to version accepted by JCAP

We present an intrinsic leptogenesis mechanism in models of axion inflation with a classical SU(2) gauge field. The gauge field is coupled to the axion with a Chern-Simons interaction and comprises a tiny fraction of the total energy, $\frac{\rho_{_{\rm YM}}}{\rho_{_{\rm tot}}}\lesssim\epsilon^2$. However, it has spin-2 fluctuations which breaks the parity and leads to the generation of chiral gravitational waves during inflation. By the gravitational anomaly in SM, it naturally creates a net lepton number density, sufficient to explain the matter asymmetry. We show that this mechanism can generate the observed value of baryon to photon number density in a natural range of parameters and yet has a small chiral tensor power spectrum on large scales., Comment: 19 pages, 1 figure

We study a single field axion inflation model in the presence of an SU(2) gauge field with a small vev. In order to make the analysis as model-independent as possible, we consider an arbitrary potential for the axion that is able to support the slow-roll inflation. The gauge field is coupled to the axion with a Chern-Simons interaction $\frac{\lambda}{f}F_{\mu\nu}^a\tilde F_a^{\mu\nu}$ where $\frac{\lambda}{f}\sim\mathcal{O}(10)$. It has a negligible effect on the background evolution, $\frac{\rho_{_{\rm YM}}}{M_{\rm Pl}^2H^2}\lesssim\epsilon^2$. However, its quantum fluctuations make a significant contribution to the cosmic perturbation. In particular, the gauge field has a spin-2 fluctuation which explicitly breaks the parity between the left- and right-handed polarization states. The chiral tensor modes are linearly coupled to the gravitational waves and lead to a circularly polarized tensor power spectrum comparable to the unpolarized vacuum power spectrum. Moreover, the scalar sector is modified by the linear scalar fluctuations of the gauge field. Since the spin-0 and spin-2 fluctuations of the SU(2) gauge field are independent, the gauge field can, at the same time, generate a detectable chiral gravitational wave signal and have a negligible contribution to the scalar fluctuations, in agreement with the current CMB observations., Comment: 34 pages, 8 figures, to appear in JHEP

In the next few years, we are going to probe the low-redshift universe with unprecedented accuracy. Among the various fruits that this will bear, it will greatly improve our knowledge of the dynamics of dark energy, though for this there is a strong theoretical preference for a cosmological constant. We assume that dark energy is described by the so-called Effective Field Theory of Dark Energy, which assumes that dark energy is the Goldstone boson of time translations. Such a formalism makes it easy to ensure that our signatures are consistent with well-established principles of physics. Since most of the information resides at high wavenumbers, it is important to be able to make predictions at the highest wavenumber that is possible. The Effective Field Theory of Large-Scale Structure (EFTofLSS) is a theoretical framework that has allowed us to make accurate predictions in the mildly non-linear regime. In this paper, we derive the non-linear equations that extend the EFTofLSS to include the effect of dark energy both on the matter fields and on the biased tracers. For the specific case of clustering quintessence, we then perturbatively solve to cubic order the resulting non-linear equations and construct the one-loop power spectrum of the total density contrast., Comment: 53 pages, 6 figures, code available at http://web.stanford.edu/~senatore/; minor corrections, version published in JCAP

In this work we study the chromo-natural inflation model in the anisotropic setup. Initiating inflation from Bianchi type-I cosmology, we analyze the system thoroughly during the slow-roll inflation, from both analytical and numerical points of view. We show that the isotropic FRW inflation is an attractor of the system. In other words, anisotropies are damped within few $e$--folds and the chromo-natural model respects the cosmic no-hair conjecture. Furthermore, we demonstrate that in the slow-roll limit, the anisotropies in both chromo-natural and gauge-flation models share the same dynamics., Comment: 15 pagers, 2 figures

We present a leptogenesis scenario associated with inflationary models involving non-Abelian gauge fields within the standard model of particle physics (SM). We show that this class of inflationary models generates intrinsic birefringent gravitational waves that through the gravitational chiral anomaly in SM, can naturally create a net lepton number density. The CP violating interaction is produced by tensor fluctuations of the gauge field, while the efficiency of this process is determined by the effective background value of the gauge field. We demonstrate that this mechanism can create the observed value of baryon to photon number density in a natural range of parameters of these models., 18 pages, 2 figures, minor comments added, version accepted for publication in PRD

In this work we revisit Wald's cosmic no-hair theorem in the context of accelerating Bianchi cosmologies for a generic cosmic fluid with non-vanishing anisotropic stress tensor and when the fluid energy momentum tensor is of the form of a cosmological constant term plus a piece which does not respect strong or dominant energy conditions. Such a fluid is the one appearing in inflationary models. We show that for such a system anisotropy may grow, in contrast to the cosmic no-hair conjecture. In particular, for a generic inflationary model we show that there is an upper bound on the growth of anisotropy. For slow-roll inflationary models our analysis can be refined further and the upper bound is found to be of the order of slow-roll parameters. We examine our general discussions and our extension of Wald's theorem for three classes of slow-roll inflationary models, generic multi-scalar field driven models, anisotropic models involving U(1) gauge fields and the gauge-flation scenario., 21 pp, 4 .eps figures

The isotropy and homogeneity of the cosmic microwave background (CMB) favors "scalar driven" early Universe inflationary models. Non-scalar fields, and in particular gauge fields, are on the other hand commonplace in all high energy particle physics models proposed to be at work at the upper bound on energy scale of inflation set by the current CMB observations. In this review we consider the role and consequences, theoretical and observational, that gauge fields can have during inflationary era. Gauge fields may be turned on in the background during inflation, or may become relevant at the level of cosmic perturbations. There have been two main class of models with gauge fields in the background, models which show violation of cosmic no-hair theorem and those which lead to isotropic FLRW cosmology, respecting the cosmic no-hair theorem. Models in which gauge fields are only turned on at the cosmic perturbation level, may source primordial magnetic fields. We also review specific observational features of these models on the CMB and/or the primordial cosmic magnetic fields. Our discussions will be mainly focused on the inflation period, with only a brief discussion on the post inflationary (p)reheating era., Comment: This is a review article prepared for Physics Reports. All comments are welcomed. 161 pages, 46 figures. v3: figures and references added, minor improvements and clarifications

We present an exhaustive analysis on the classical solutions of the Chromo-natural model. We showed that starting from an arbitrary axion field value $\chi_0\in(0,f\pi)$, it is possible to have successful slow-roll inflation and working out the analytical solution of the number of e-folding, we determine the allowed region of the parameters corresponding to each $\chi_0$ value. Having the allowed parameter region, then we study the behavior of the solutions respect to the initial value of the axion field., Comment: 7 pages, 7 figures

A scenario of leptogenesis was introduced in [1] which works during inflationary period within standard model of particle physics setup. In this scenario lepton number is created by the gravitational chiral anomaly which has a non-zero expectation value for models of inflation driven by pseudoscalar field(s). Here, we observe that models of inflation involving non-Abelian gauge fields, e.g. the chromo-natural inflation [2] or the gauge-flation [3], have a parity-violating tensor mode (graviton) spectrum and naturally lead to a non-vanishing expectation value for the gravitational chiral anomaly. Therefore, one has a natural leptogenesis scenario associated with these inflationary setups, \emph{inflato-natural leptogenesis}. We argue that the observed value of baryon-to-photon number density can be explained in a natural range of parameters in these models., Comment: matches published version

Inflationary models are usually based on dynamics of one or more scalar fields coupled to gravity. In this work we present a new class of inflationary models, gauge-flation or non-Abelian gauge field inflation, where slow-roll inflation is driven by a non-Abelian gauge field. This class of models are based on a gauge field theory with a generic non-Abelian gauge group minimally coupled to gravity. We then focus on a particular gauge-flation model by specifying the action for the gauge theory which allows for a successful slow-roll inflation. This model has two parameters the value of which can be fixed using the CMB and other cosmological data. These values are within the natural range of parameters in generic grand unified theories of particle physics., Revtex4-1 format, 5 pages, v4: cosmic perturbation theory improved

In [arXiv:1102.1513] we introduced an inflationary scenario, Non-Abelian Gauge Field Inflation or gauge-flation for short, in which slow-roll inflation is driven by non-Abelian gauge field minimally coupled to gravity. We present a more detailed analysis, both numerical and analytical, of the gauge-flation. By studying the phase diagrams of the theory, we show that getting enough number of e-folds during a slow-roll inflation is fairly robust to the choice of initial gauge field values. In addition, we present a detailed analysis of the cosmic perturbation theory in gauge-flation which has many special and interesting features compared the standard scalar-driven inflationary models. The specific gauge-flation model we study in this paper has two parameters, a cutoff scale Lambda and the gauge coupling g. Fitting our results with the current cosmological data fixes \Lambda\sim 10 H \sim 10^{15} GeV (H is the Hubble parameter) and g\sim 10^{-4}, which are in the natural range of parameters in generic particle physics beyond standard models. Our model also predicts a tensor-to-scalar ratio r>0.05, in the range detectable by the Planck satellite., Comment: 49 pages, 23 figures. v5: Cosmic perturbation analysis improved

Gauge-flation, inflation from non-Abelian gauge fields, was introduced in [1,2]. In this work, we study the cosmic no-hair conjecture in gauge-flation. Starting from Bianchi-type I cosmology and through analytic and numeric studies we demonstrate that the isotropic FLRW inflation is an attractor of the dynamics of the theory and that the anisotropies are damped within a few e-folds, in accord with the cosmic no-hair conjecture., Comment: 24 pages, 18 figures