We introduce a novel mechanism where processes that preserve the number density of the dark sector set the relic density of a thermal particulate dark matter. In a relatively degenerate multipartite dark sector, if there is a considerable time lapse between the freeze out of various species, then a process like exchange between dark sector constituents can play the pivotal role of driving freeze out and setting dark matter relic density. As a proof of principle, we present simple scalar models with viable dark matter in the GeV scale to demonstrate this phenomenon.

The recent IceCube publication claims the observation of cosmic neutrinos with energies down to $\sim 10\mathrm{TeV}$, reinforcing the growing evidence that the neutrino flux in the 10–100 TeV range is unexpectedly large. Any conceivable source of these neutrinos must also produce a $\gamma$-ray flux which degrades in energy en route to the Earth and contributes to the extragalactic $\gamma$-ray background measured by the Fermi satellite. In a quantitative multimessenger analysis, featuring minimalistic assumptions, we find a $\gtrsim 3\sigma$ tension in the data, reaching $\sim 5\sigma$ for cosmic neutrinos extended down to $\sim 1\mathrm{TeV}$, interpreted as evidence for a population of hidden cosmic-ray accelerators.

In the framework of the Standard Model, we present predictions for partial widths, double and single differential distributions, and forward-backward lepton asymmetries for four-leptonic decays $B^{-}\to {\mu }^{+}{\mu }^{-}{\overline{\nu }}_e{e}^{-}$, $B^{-}\to e^{+}{e}^{-}{\overline{\nu }}_{\mu }{\mu }^{-}$, $B^{-}\to {\mu }^{+}{\mu }^{-}{\overline{\nu }}_{\mu }{\mu }^{-}$, and $B^{-}\to e^{+}{e}^{-}{\overline{\nu }}_e{e}^{-}$. We consider the contributions of virtual photon emission from the light and heavy quarks of the $B^{-}$ meson, and we include bremsstrahlung of a virtual photon from the charged lepton in the final state. We use the model of vector meson dominance for calculation of virtual photon emission by the light quark of the $B^{-}$ meson and take into account the isotopic correction. The dependence of branchings on the relative phase of the contributions of the light intermediate vector mesons is studied.

We present a nonextensive version of the Polyakov–Nambu–Jona-Lasinio model which is based on the nonextensive statistical mechanics. This new statistics is characterized by a dimensionless nonextensivity parameter $q$ that accounts for all possible effects violating the assumptions of the Boltzmann-Gibbs statistics (when $q\to 1$, it returns to the Boltzmann-Gibbs case). Using this q-Polyakov–Nambu–Jona-Lasinio model and including two different Polyakov-loop potentials, we discussed the influence of the parameter $q$ on chiral and deconfinement phase transition, various thermodynamic quantities and transport coefficients at finite temperature and zero quark chemical potential. We found that the Stefan-Boltzmann (SB) limit is actually related to the choice of statistics. For example, in the Tsallis statistics, the thermodynamic quantities $\frac{\epsilon }{T^4}$, $\frac{p}{T^4}$, and $\frac{s}{T^3}$ all increase with $q$, exceed their usual SB limits, and tend to a new $q$-related Tsallis limit at temperature high enough. Interestingly, however, due to a surprising cancellation, the high temperature limit of $c_s^2$ is still its SB limit $1/3$. In addition, we found some similarities between the nonextensive effect and the finite-size effect. For example, as $q$ increases (size decreases), the criticality of $\frac{c_v}{T^3}$ and $c_s^2$ gradually disappears. Besides, in order to better study the nonextensive effect, we defined a new susceptibility and calculated the response of thermodynamic quantities and transport coefficients to $q$. And found that their response patterns are different.

A formally exact discrete multiresolution representation of quantum field theory on a light front is presented. The formulation uses an orthonormal basis of compactly supported wavelets to expand the fields restricted to a light front. The representation has a number of useful properties. First, light-front preserving Poincaré transformations can be computed by transforming the arguments of the basis functions. The discrete field operators, which are defined by integrating the product of the field and a basis function over the light front, represent localized degrees of freedom on the light-front hyperplane. These discrete fields are irreducible and the vacuum is formally trivial. The light-front Hamiltonian and all of the Poincaré generators are linear combinations of normal ordered products of the discrete field operators with analytically computable constant coefficients. The representation is discrete and has natural resolution and volume truncations like lattice formulations. Because it is formally exact, it is possible to systematically compute corrections for eliminated degrees of freedom.

We study the Casimir effect in the classical geometry of two parallel conductive plates, separated by a distance $L$, for a Lorentz-breaking extension of the scalar field theory. The Lorentz-violating part of the theory is characterized by the term $\lambda {(u·\partial \varphi )}^2$, where the parameter $\lambda$ and the background four-vector $u^{\mu }$ codify Lorentz symmetry violation. We use Green’s function techniques to study the local behavior of the vacuum stress-energy tensor in the region between the plates. Closed analytical expressions are obtained for the Casimir energy and pressure. We show that the energy density ${\mathcal{E}}_C$ (and hence the pressure) can be expressed in terms of the Lorentz-invariant energy density ${\mathcal{E}}_0$ as follows ${\mathcal{E}}_C(L)=\sqrt{\frac{1-\lambda u_n^2}{1+\lambda u^2}}{\mathcal{E}}_0(\tilde{L}),$ where $\tilde{L}=L/\sqrt{1-\lambda u_n^2}$ is a rescaled plate-to-plate separation and $u_n$ is the component of $\overrightarrow{u}$ along the normal to the plates. As usual, divergences of the local Casimir energy do not contribute to the pressure.

The present work investigates the possibility that both dark matter and the anomalous magnetic moment of the muon may be explained within the context of the inverse seesaw extended next-to-minimal supersymmetric Standard Model (ISS-NMSSM). In ISS-NMSSM, the newly introduced Higgs-neutrino Yukawa coupling $Y_{\nu }$ provides additional Higgsino-sneutrino loop contribution to $(g-2{)}_{\mu }$. If the deviation between the experimental observations and the Standard Model predictions of the anomalous muon magnetic moment is confirmed by the further experimental and theoretical studies, it can be explained naturally within the ISS-NMSSM framework without conflicting with the current stringent limits on the direct detection of dark matter and Large Hadron Collider searches.

In this paper, the inclusive Pomeron-Pomeron, Reggeon-Reggeon, Pomeron-Reggeon as well as gluon-Pomeron(-Reggeon) and photon-Pomeron(-Reggeon) interactions for the ${\eta }_{\mathrm{c}}$ at the LHC energies have been examined in proton-proton, proton-nucleus and nucleus-nucleus collision modes. The cross section has been computed based on the NRQCD factorization and Regge theory formalism. The cross exchange of Pomeron-Reggeon contribution is important in pp and pA modes. The Pomeron-Pomeron contribution is significant in AA mode. The Pomeron contribution is considerable for AA and pA modes in single diffractive process where A undergoes the diffractive process. Reggeon contribution is sizable in pp and pA modes where p only undergoes the diffractive process. The Pomeron and Reggeon contributions in photon-Pomeron and-Reggeon process remain smaller than that of gluon-Pomeron and-Reggeon processes. Our results show that the experimental study of Reggeon, Pomeron and their cross exchange can be carried out in certain kinematic windows with the specific choice of the mode at the LHC. The investigation can be useful to better constrain the Reggeon and Pomeron parton content. The inclusive process serves as the background to related exclusive processes which should be predicted.

We consider the matrix regularization of fields on a Riemann surface which couple to gauge fields with a nonvanishing magnetic flux. We show that such fields are described as rectangular matrices in the matrix regularization. We construct the matrix regularization explicitly for the case of the sphere and torus based on the Berezin-Toeplitz quantization, and also discuss a possible generalization to cases with higher genera. We also discuss the matrix version of the Laplacian acting on the rectangular matrices.

In this work, we show that one can select different types of hypergeometric approximants for the resummation of divergent series with different large-order growth factors. Being of $n!$ growth factor, the divergent series for the $ϵ$ expansion of the critical exponents of the $O(N)$-symmetric model is approximated by the hypergeometric functions ${{}_{k+1}F}_{k-1}$. The divergent ${{}_{k+1}F}_{k-1}$ functions are then resummed using their equivalent Meijer-G function representation. The convergence of the resummation results for the exponents $\nu$, $\eta$, and $\omega$ has been shown to improve systematically in going from low order to the highest known six-loop order. Our six-loop resummation results are very competitive to the recent six-loop Borel with conformal mapping predictions and to recent Monte Carlo simulation results. To show that precise results extend for high $N$ values, we listed the five-loop results for $\nu$ which are very accurate as well. The recent seven-loop order ($g$ series) for the renormalization group functions $\beta ,{\gamma }_{{\varphi }^2}$, and ${\gamma }_{m^2}$ has been resummed too. Accurate predictions for the critical coupling and the exponents $\nu$, $\eta$, and $\omega$ have been extracted from $\beta$, ${\gamma }_{{\varphi }^2}$, and ${\gamma }_{m^2}$ approximants.

We consider the gravitational collapse of a self-gravitating spherical dust cloud in the Hamiltonian formalism. We address both homogeneous and inhomogeneous cases. Our novel derivation of the Hamiltonian of the system is based on an improved variational principle. It differs from usual treatments due to the presence of an extra boundary term added to the Hilbert action. As expected, the standard equations of motion are retrieved. However, differently from other treatments, the total Hamiltonian obtained with our procedure in the Schwarzschild time gauge is identical to the total mass of the system as measured from infinity, as it would be expected. Implications for the quantization of the system are suggested.

We study cosmological tensor perturbations induced by second-order scalar perturbations in the presence of anisotropic non-Gaussianity. This class of induced tensor modes arises on superhorizon scales through the anisotropic coupling between long modes and short modes. We show that scalar perturbations on the inflationary Hubble scale to the Silk damping scale at recombination contribute to the induced tensor powerspectrum at the cosmic microwave background (CMB) scale, and that the induced tensor spectrum becomes almost scale-invariant. The former property suggests that measurements of the CMB offer a test of tiny scale physics. However, the latter implies the secondary effect may contaminate the primordial tensor spectrum, which tells us the energy scale of inflation. We derive the induced tensor modes originated from two concrete examples of anisotropic non-Gaussianity; statistically anisotropic scalar non-Gaussianity and scalar-scalar-tensor non-Gaussianity, and discuss observational consequences of extremely short scale physics. Also, we comment on various possibilities of enhancing the induced spectrum with nonstandard early Universe physics.

Perturbations from inflation evolve into large scale structure of the late universe, and encode abundant cosmic structure formation physics. We allow freedom in the primordial power spectrum, rather than assuming a power law scale dependence, to study its impact on cosmological parameter determination. Combining various generations of cosmic microwave background (CMB) data and galaxy redshift survey data, we investigate the constraints on reconstruction of the primordial curvature perturbation power spectrum and the late time cosmology, especially the sum of neutrino masses. We quantify how each successive generation, in CMB and galaxy surveys, provides significant improvements, often by factors of several. By using CMB polarization information over a broad range of angular scales, and galaxy redshift data in many bins of redshift, one can allow inflationary freedom and still constrain parameters comparably to assuming power law dependence. The primordial power spectrum can be reconstructed at the subpercent level in a dozen wave number bins, while simultaneously fitting the sum of neutrino masses to 14 meV.

General relativity (GR) predicts concordant trajectories for photons and gravitational waves (GWs). We propose a new multimessenger avenue (GW-CMB-CMB) to prove this aspect of fundamental physics by cross-correlating the GW signal of astrophysical origin with the lensing field derived from the cosmic microwave background (CMB). This new window will allow robust measurement of the prediction from GR with high signal-to-noise ratio and will be able to unveil the true nature of gravity using the GW sources detected by missions such as the Laser Interferometer Space Antenna, Einstein Telescope, and Cosmic Explorer.

We analyze two dedicated NuSTAR observations with exposure $\sim 190\mathrm{ks}$ located $\sim 10°$ from the Galactic plane, one above and the other below, to search for x-ray lines from the radiative decay of sterile-neutrino dark matter. These fields were chosen to minimize astrophysical x-ray backgrounds while remaining near the densest region of the dark matter halo. We find no evidence of anomalous x-ray lines in the energy range 5–20 keV, corresponding to sterile neutrino masses 10–40 keV. Interpreted in the context of sterile neutrinos produced via neutrino mixing, these observations provide the leading constraints in the mass range 10–12 keV, improving upon previous constraints in this range by a factor $\sim 2$. We also compare our results to Monte Carlo simulations, showing that the fluctuations in our derived limit are not dominated by systematic effects. An updated model of the instrumental background, which is currently under development, will improve NuSTAR’s sensitivity to anomalous x-ray lines, particularly for energies 3–5 keV.

We study the thermodynamic history of composite dark matter models. We start with classifying the models by means of the symmetries partially protecting the composite dark matter decays and constrain their lifetimes. For each model, we determine the impact of number-changing and number-conserving operators on its thermal history. We also develop the analytic formalism to calculate the asymptotic abundance of stable relics. We show how the relative strength between number- changing and number-conserving interactions together with the dark plasma lifetime affect the thermal fate of the various composite models. Additionally, we show that the final dark relic density of composite particles can be diluted due to an entropy increase stemming from dark plasma decay. Finally, we confront the models with experimental bounds. We find that indirect detection experiments are most promising in testing this large class of models.

Electron-positron pair production in spatially and temporally inhomogeneous electric and magnetic fields is studied within the Dirac-Heisenberg-Wigner formalism (quantum kinetic theory) through computing the corresponding Wigner functions. The focus is on discussing the particle momentum spectrum regarding signatures of Schwinger and multiphoton pair production. Special emphasis is put on studying the impact of a strong dynamical magnetic field on the particle distribution functions. As the equal-time Wigner approach is formulated in terms of partial integro-differential equations an entire section of the manuscript is dedicated to present numerical solution techniques applicable to Wigner function approaches in general.

The potential of $n$-Higgs doublet models ($n\mathrm{HDMs}$) contains a large number of ${\mathrm{SU}(2)}_L$-preserving accidental symmetries as subgroups of the symplectic group $\mathrm{Sp}(2n)$. To classify these, we introduce prime invariants and irreducible representations in bilinear field space that enable us to explicitly construct accidentally symmetric $n\mathrm{HDM}$ potentials. We showcase the classifications of symmetries and present the relationship among the theoretical parameters of the scalar potential for the following: (i) the two Higgs doublet model (2HDM), and (ii) the three Higgs doublet model (3HDM). We recover the maximum number of 13 accidental symmetries for the 2HDM potential, and for the first time, we present the complete list of 40 accidental symmetries for the 3HDM potential.