Constant roll inflation is analyzed in the presence of multiscalar fields which are assumed to be described by a constant roll rate each. The different cases are studied and the corresponding potentials are reconstructed. The exact solutions are obtained, which show a similar behavior to the single scalar field model. For one of the cases analyzed in the paper, the so-called adiabatic field also constantly roll(s) while entropy perturbations become null, while the second case may lead to nonadiabatic perturbations. Both cases can fit the Planck data well by assuming the appropriate values for the free parameters of the models.

The coherent oscillation of axionic fields naturally drives copious production of dark photon particles in the early Universe, due to resonance and tachyonic enhancement. During the process, energy is abruptly transferred from the former to the latter, sourcing gravitational-wave generation. The resulting gravitational waves are eventually observed today as stochastic background. We report analytical results of this production and connect them to the recent pulsar-timing results from the NANOGrav Collaboration. We show an available parameter space for our mechanism to account for the signal around the mass $m_{\varphi }\sim {10}^{-13}\mathrm{eV}$ and the decay constant $f_{\varphi }\sim {10}^{16}\mathrm{GeV}$, with a dimensionless coupling of $\mathcal{O}(1)$. A mechanism to keep the axion from dominating the Universe is a necessary ingredient of this model, and we discuss a possibility to recover a symmetry and render the axion massless after the production. We also comment on potential implications of the required effective number of relativistic species for the determination of the present Hubble constant.

Chiral perturbation theory (ChPT) is a low-energy effective field theory of QCD and also a nonlinear sigma model based on the symmetry breaking pattern $\mathrm{SU}(N_f)\times \mathrm{SU}(N_f)\to \mathrm{SU}(N_f)$. In the limit of massless $N_f$ quarks, we enumerate the independent operators without external sources in ChPT using an on-shell method, by counting and presenting the soft blocks at each order in the derivative expansion, up to $\mathcal{O}(p^{10})$. Given the massless on-shell condition and total momentum conservation, soft blocks are homogeneous polynomials of kinematic invariants exhibiting Adler’s zero when any external momentum becomes soft and vanishing. In addition, soft blocks are seeds for recursively generating all tree amplitudes of Nambu-Goldstone bosons without recourse to ChPT, and in one-to-one correspondence with the “low-energy constants” which are the Wilson coefficients. Relations among operators, such as those arising from equations of motion, integration by parts, Hermiticity, and symmetry structure, manifest themselves in the soft blocks in simple ways. We find agreements with the existing results up to next-to-next-to-next-to-leading order (NNNLO) and make a prediction at ${\mathrm{N}}^4\mathrm{LO}$.

We investigate the impact of correlations between (theoretical and experimental) uncertainties on multi-experiment, multi-observable analyses within the standard model effective field theory (SMEFT). To do so, we perform a model-independent analysis of $t$-channel single top-quark production and top-quark decay data from ATLAS, CMS, CDF, and D0. We show quantitatively how the fit changes when different experimental or theoretical correlations are assumed. Scaling down statistical uncertainties according to the luminosities of future colliders with $300{\mathrm{fb}}^{-1}$ and higher, we find that this effect becomes a matter of life and death: assuming no correlations returns a fit in agreement with the standard model while a “best guess”-ansatz taking into account correlations would observe new physics. At the same time, modeling the impact of higher order SMEFT-corrections the latter turn out to be a subleading source of uncertainty only.

The perturbative procedure of matching was proposed to connect parton quasidistributions that are calculable in lattice QCD to the corresponding light cone distributions which enter physical processes. Such a matching procedure has so far been limited to the twist-2 distributions. Recently, we addressed the matching for the twist-3 PDF $g_T(x)$. In this work, we extend our perturbative calculations to the remaining twist-3 PDFs, $e(x)$ and $h_L(x)$. In particular, we discuss the nontrivialities involved in the calculation of the singular zero-mode contributions for the quasi-PDFs.

In view of the importance of the nonperturbative resolved contributions for the overall uncertainties of the two inclusive penguin decays $\overline{B}\to X_s\gamma$ and $\overline{B}\to X_{s,d}{\ell }^{+}{\ell }^{-}$, we reanalyze these contributions using new estimates of moments of the subleading shape functions and of other input parameters. Within a systematic approach, we find a significant reduction of the nonperturbative uncertainties in the inclusive decay $\overline{B}\to X_{s,d}{\ell }^{+}{\ell }^{-}$, but a much less pronounced reduction in the inclusive decay $\overline{B}\to X_s\gamma$ compared to a recent analysis on the resolved contributions to the inclusive decay $\overline{B}\to X_s\gamma$. We identify the reasons for this discrepancy.

The observed cross sections for $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}$ at energies from 3.8 to 4.6 GeV are measured using data samples taken with the BESIII detector operated at the BEPCII collider. We measure the muonic widths and determine the branching fractions of the charmonium states $\psi (4040)$, $\psi (4160)$, and $\psi (4415)$ decaying to ${\mu }^{+}{\mu }^{-}$, as well as making a first determination of the phase of the amplitudes. In addition, we observe evidence for a structure in the dimuon cross section near $4.220\mathrm{GeV}/c^2$, which we denote as $S(4220)$. Analyzing a coherent sum of amplitudes yields eight solutions, one of which gives a mass of $M_{S(4220)}=4216.7\pm 8.9\pm 4.1\mathrm{MeV}/c^2$, a total width of ${\mathrm{\Gamma }}_{\mathrm{S}(4220)}^{\mathrm{tot}}=47.2\pm 22.8\pm 10.5\mathrm{MeV}$, and a muonic width of ${\mathrm{\Gamma }}_{S(4220)}^{\mu \mu }=1.53\pm 1.26\pm 0.54\mathrm{keV}$, where the first uncertainties are statistical and the second systematic. The eight solutions give the central values of the mass, total width, muonic width to be, respectively, in the range from 4212.8 to $4219.4\mathrm{MeV}/c^2$, from 36.4 to 49.6 MeV, and from 1.09 to 1.53 keV. The statistical significance of the $S(4220)$ signal is $3.9\sigma$. Correcting the total dimuon cross section for radiative effects yields a statistical significance for this structure of $8.1\sigma$.

We analyze the holographic entanglement entropy in a soliton background with a background gauge field and derive a relation analogous to the first law of thermodynamics. The confinement/deconfinement phase transition occurs due to the competition of two minimal surfaces. The entropic C function probes the confinement/deconfinement phase transition. It is sensitive to the degrees of freedom smaller than the size of a spatial circle. When the background gauge field becomes large, the entropic C function becomes nonmonotonic as a function of the size and does not satisfy the usual c-theorem. We analyze the entanglement entropy for a small subregion and the relation analogous to the first law of thermodynamics. For the small amount of a background gauge field, the excited amount of the entanglement entropy decreases from the ground state. It reflects that confinement decreases degrees of freedom. We finally discuss the second order correction of the holographic entanglement entropy.

By a generalization of the Hopfield model, we construct a microscopic Lagrangian describing a dielectric medium with dispersion and dissipation. This facilitates a well-defined and unambiguous ab initio treatment of quantum electrodynamics in such media, even in time-dependent backgrounds. As an example, we calculate the number of photons created by switching on and off dissipation in dependence on the temporal switching function. This effect may be stronger than quantum radiation produced by variations of the refractive index $\mathrm{\Delta }n(t)$ since the latter are typically very small and yield photon numbers of order $(\mathrm{\Delta }n{)}^2$. As another difference, we find that the partner particles of the created medium photons are not other medium photons but excitations of the environment field causing the dissipation (which is switched on and off).

We study the gravitational waves emitted by an inspiraling compact binary system in massive Brans-Dicke theory. In addition to the two tensor polarizations, which have been obtained in previous work, we explicitly and analytically calculate the expressions for the time-domain waveforms of the two scalar polarizations. With the stationary phase approximations, we obtain the Fourier transforms of the two tensor polarizations. We find that when the scalar field is light, the waveforms can be mapped to the parametrized post-Einsteinian (ppE) framework, and we identify the ppE parameters. However, when the scalar field is heavy, the ppE framework is not applicable. We also obtain the projected constraints on the parameters of this theory by gravitational wave observations of future ground-based detectors. Finally, we apply our result to the model proposed by Damour and Esposito-Farèse, $f(R)$ gravity, and screened modified gravity.

In this work, we investigate a new warped five-dimensional, $Z_2$-symmetric thick brane solution in the presence of a real scalar field. We examine the different geometric aspects of the model. We discuss the stability of the solution under gravitational fluctuations and study both the graviton ground state and the continuum of Kaluza-Klein modes to find a correction to Newton’s law. Then, we study the quantum version of the model by deriving the Wheeler-DeWitt equation and looking for the corresponding solution. Finally, the cosmology of the brane is studied.

We study the evolution of axions interacting with primordial magnetic fields (PMFs) starting from the QCD phase transition in the expanding Universe. This interaction is owing to the Primakoff effect. Adopting the zero-mode approximation for axions, we derive the system of equations for axions and magnetic fields, where the expansion of the Universe and the spectra of magnetic fields are accounted for exactly. We find that the contribution of the Primakoff effect to the dynamics of axions and magnetic fields is rather weak. This confirms some previous estimates leading to analogous conclusions when we account for the Hubble expansion for both a uniform axion field and nonuniform PMFs using Fourier spectra for their energy and helicity densities. We solve the corresponding system of the evolution equations and find that the amplitude of the axion zero mode, when evolving during the radiation era, is at a level sufficient for the axion to be a good candidate for cold dark matter.

We formulate Barrow holographic dark energy, by applying the usual holographic principle at a cosmological framework, but using the Barrow entropy instead of the standard Bekenstein-Hawking one. The former is an extended black-hole entropy that arises due to quantum-gravitational effects which deform the black-hole surface by giving it an intricate, fractal form. We extract a simple differential equation for the evolution of the dark-energy density parameter, which possesses standard holographic dark energy as a limiting subcase, and we show that the scenario can describe the thermal history of the universe, with the sequence of matter and dark-energy eras. Additionally, the new Barrow exponent $\mathrm{\Delta }$ significantly affects the dark-energy equation of state, and according to its value it can lead it to lie in the quintessence regime, in the phantom regime, or experience the phantom-divide crossing during the evolution.

Rapidly rotating black holes are known to develop instabilities in the presence of a sufficiently light boson, a process which becomes efficient when the boson’s Compton wavelength is roughly the size of the black hole. This phenomenon known as black hole superradiance generates an exponentially growing boson cloud at the expense of the rotational energy of the black hole. For astrophysical black holes with $M\sim \mathcal{O}(10)M_{\odot }$, the superradiant condition is achieved for bosons with $m_b\sim \mathcal{O}({10}^{-11})\mathrm{eV}$; intriguingly, photons traversing the intergalactic medium acquire an effective mass (due to their interactions with the ambient plasma) which naturally resides in this range. The implications of photon superradiance, i.e., the evolution of the superradiant photon cloud and ambient plasma in the presence of scattering and particle production processes, have yet to be thoroughly investigated. Here, we enumerate and discuss a number of different processes capable of quenching the growth of the photon cloud, including particle interactions with the ambient electrons and backreactions on the effective mass (arising e.g., from thermal effects, pair production, ionization of the local background, and modifications to the dispersion relation from strong electric fields). This work naturally serves as a guide in understanding how interactions may allow light exotic bosons to evade superradiant constraints.

Primary very high energy $\gamma$ rays from $\gamma$-ray bursts (GRBs) are partially absorbed on extragalactic background light photons with subsequent formation of intergalactic electromagnetic cascades. Characteristics of the observable cascade $\gamma$-ray signal are sensitive to the strength and structure of the extragalactic magnetic field (EGMF). GRB 190114C was recently detected with the MAGIC imaging atmospheric Cherenkov telescopes, for the first time allowing us to estimate the observable cascade intensity. We inquire whether any constraints on the EGMF strength and structure could be obtained from publicly available $\gamma$-ray data on GRB 190114C. We present detailed calculations of the observable cascade signal for various EGMF configurations. We show that the sensitivity of the Fermi-LAT space $\gamma$-ray telescope is not sufficient to obtain such constraints on the EGMF parameters. However, next-generation space $\gamma$-ray observatories such as MAST would be able to detect pair echoes from GRBs similar to GRB 190114C for the EGMF strength below ${10}^{-17}–{10}^{-18}\mathrm{G}$.

The magnetic polarizability of the neutral pion has been calculated in the background magnetic-field formalism of lattice QCD. In this investigation, the chiral extrapolation of these lattice results is considered in a formalism preserving the exact leading nonanalytic terms of chiral perturbation theory. The $n_f=2+1$ numerical simulations are electro-quenched, such that the virtual sea quarks of the QCD vacuum do not interact with the background field. To understand the impact of this, we draw on partially quenched chiral perturbation theory and identify the leading contributions of quark-flow connected and disconnected diagrams. While electro-quenching does not impact the leading-loop contribution to the magnetic polarizability, the loops which generate the leading term have yet to be considered in lattice QCD simulations. Lattice QCD results are used to constrain the analytic terms in the chiral expansion and supplementing those with the two-loop result from chiral perturbation theory enables an evaluation of the polarizability at the physical quark mass. The resulting magnetic polarizability of the neutral pion is ${\beta }_{{\pi }^0}=3.44(19{)}^{\mathrm{stat}}(37{)}^{\mathrm{syst}}\times {10}^{-4}{\mathrm{fm}}^3$, which lies just above the $1\sigma$ error bound of the experimental measurement.

We study the chiral phase transition inside a rotating cylinder within the framework of the Nambu–Jona-Lasinio model. A spectral boundary condition is imposed to avoid faster than light. We investigate how the geometry of the cylinder and rotation influence the chiral phase transition at finite temperature and chemical potential. The inhomogeneous effects caused by the finite size and rotation are also taken into account. It is found that finite size will reduce the chiral transition temperature and raises the chiral transition chemical potential, while the rotation reduces both the chiral transition temperature and chemical potential. In addition, we discuss the implications of our results in heavy-ion collisions and equation of states of neutron star.

Recently, an improved quenching factor (QF) measurement for low-energy nuclear recoils in CsI[Na] has been reported by the COHERENT Collaboration. The new energy-dependent QF is characterized by a reduced systematic uncertainty and leads to a better agreement between the experimental COHERENT data and the Standard Model (SM) expectation. In this work, we report updated constraints on parameters that describe the process of coherent elastic neutrino-nucleus scattering within and beyond the SM, and we also present how the new QF affects their interpretation.

During the last fifty-one years, the effect of excitation of the quantum vacuum field induced by its coupling with a moving object has been systematically studied. Here, we propose and investigate a somewhat inverted setting: an object, initially at rest, whose motion becomes induced by an excitation of the quantum vacuum caused by the object itself. In the present model, this excitation occurs asymmetrically on different sides of the object by a variation in time of one of its characteristic parameters, which couple it with the quantum vacuum field.

The rapid advancement of gravitational wave astronomy in recent years has paved the way for the burgeoning development of black hole spectroscopy, which enhances the possibility of testing black holes by their quasinormal modes (QNMs). In this paper, the axial gravitational perturbations and the QNM frequencies of black holes in the hybrid metric-Palatini gravity (HMPG) are investigated. The HMPG theory is characterized by a dynamical scalar degree of freedom and is able to explain the late-time accelerating expansion of the universe without introducing any ad hoc screening mechanism to preserve the dynamics at the Solar System scale. We obtain the master equation governing the axial gravitational perturbations of the HMPG black holes and calculate the QNM frequencies. Moreover, in the scrutiny of the black holes and their QNMs, we take into account the constraints on the model parameters based on the post-Newtonian analysis, and show how the QNM frequencies of the HMPG black holes would be altered in the observationally consistent range of parameter space.