Within the framework of the standard model (SM), using the facility of weak basis (WB) transformations, the general Dirac neutrino mass matrix and the charged lepton mass matrix can essentially be considered as texture two zero mass matrices. Using type I seesaw formula for Majorana neutrino mass matrix, our analysis yields lower bounds $m_{ee}\gtrsim 0.001\mathrm{eV}$ for normal mass ordering and $m_{ee}\gtrsim 0.08\mathrm{eV}$ for inverted mass ordering, the latter being tantalizingly close to the expected outcome of the ongoing experiments. Interestingly, for inverted mass ordering, $m_{ee}$ is largely independent of variation of mass $m_3$, whereas, for normal mass ordering with $m_1$ in the range 0.0001 eV–0.01 eV, the bound on parameter $m_{ee}$ gets further sharpened and one obtains $m_{ee}$ within the band 0.014–0.042 eV. Further, noting that a particular set of texture four zero quark mass matrices has been shown to be a unique viable option for the description of quark mixing data, an analysis of similar mass matrices in the lepton sector has also been carried out to obtain bounds for the parameter $m_{ee}$ with interesting consequences.

We evaluate the relative entropy on a ball region near the UV fixed point of a holographic conformal field theory deformed by a fermionic operator of nonzero vacuum expectation value. The positivity of the relative entropy considered here is implied by the expected monotonicity of the decrease of quantum entanglement under the renormalization group flow. The calculations are done in the perturbative framework of Einstein-Cartan gravity in four-dimensional asymptotic anti–de Sitter space with a postulated standard bilinear coupling between the axial fermion current and torsion. By requiring positivity of relative entropy, our result yields a constraint on axial current–torsion coupling, fermion mass, and equation of state.

We analyze how excitations affect the entanglement entropy for an arbitrary entangling interval in a 2d conformal field theory (CFT) using the holographic entanglement entropy techniques as well as direct CFT computations. We introduce the excitation entanglement entropy ${\mathrm{\Delta }}_{h}S$, the difference between the entanglement entropy generic excitations and their arbitrary conformal descendants denoted through $h$. The excitation entanglement entropy, unlike the entanglement entropy, is a finite quantity (independent of the cutoff), and hence a good physical observable. We show that the excitation entanglement entropy for any given interval is uniquely specified by a local second order differential equation sourced by the one point function of the energy momentum tensor computed in the excited background state, and two boundary and smoothness conditions. We analyze low and high temperature behavior of the excitation entanglement entropy and show that ${\mathrm{\Delta }}_{h}S$ grows as a function of temperature. We prove an “integrated positivity” for the excitation entanglement entropy, that although ${\mathrm{\Delta }}_{h}S$ can be positive or negative, its average value is always positive. We also discuss the mutual and multipartite information and (strong) subadditivity inequality in the presence of generic excitations and their conformal descendants.

Previous analytical studies of quantum electrodynamics in $2+1$ dimensions (QED3) have shown the existence of a critical number of fermions for onset of chiral symmetry breaking, the most known being the value $N_c\approx 3.28$ obtained by Nash to $1/N^2$ order in the $1/N$ expansion [D. Nash, Phys. Rev. Lett. 62, 3024 (1989)]. This analysis is reconsidered by solving the Dyson-Schwinger equations for the fermion propagator and the vertex to show that the more accurate gauge-independent value is $N_c\approx 2.85$, which means that the chiral symmetry is dynamically broken for integer values $N\le 2$, while for $N\ge 3$ the system is in a chirally symmetric phase. An estimate for the value of chiral condensate $⟨\overline{\psi }\psi ⟩$ is given for $N=2$. Knowing precise $N_c$ would be important for comparison between continuum studies and lattice simulations of QED3.

We consider the Einstein-Maxwell-Klein-Gordon equations for a spherically symmetric scalar field scattering off a Reissner-Nordström black hole in asymptotically flat spacetime. The equations are solved numerically using a hyperboloidal evolution scheme. For suitable frequencies of the initial data, superradiance is observed, leading to a substantial decrease of mass and charge of the black hole. We also derive a Bondi mass loss formula using the Kodama vector field and investigate the late-time decay of the scalar field.

We compute the parametrized post-Newtonian parameter $\gamma$ in the case of a static point source for multiscalar-tensor gravity with completely general nonderivative couplings and potential in the Jordan frame. Similarly to the single massive field case $\gamma$ depends exponentially on the distance from the source and is determined by the length of a vector of nonminimal coupling in the space of scalar fields and its orientation relative to the mass eigenvectors. Using data from the Cassini tracking experiment, we estimate bounds on a general theory with two scalar fields. Our formalism can be utilized for a wide range of models, which we illustrate by applying it to nonminimally coupled Higgs SU(2) doublet, general hybrid metric-Palatini gravity, linear (${\square }^{-1}$) and quadratic (${\square }^{-2}$) nonlocal gravity.

We consider the possibility of an interaction in the dark sector in the presence of massive neutrinos and study the observational constraints on three different scenarios of massive neutrinos using the most recent cosmic microwave background anisotropy data in combination with type Ia supernovae, baryon acoustic oscillations, and Hubble parameter measurements. When a sterile neutrino is introduced into the interacting dark sector scenario in addition to the standard model prediction of neutrinos, we find that the coupling parameter is nonzero at a $2\sigma$ confidence level. The interaction model with a sterile neutrino is also found to be a promising one to alleviate the current tension on the Hubble constant. We do not find the evidence for a coupling in the dark sector when the possibility of a sterile neutrino is discarded.

The extended quasidilaton theory is one of the simplest Lorentz-invariant massive gravity theories which can accommodate a stable self-accelerating vacuum solution. In this paper we revisit this theory and study the effect of matter fields. For a matter sector that couples minimally to the physical metric, we find hints of a Jeans type instability in the IR. In the analogue k-essence field setup, this instability manifests itself as an IR ghost for the scalar field perturbation, but this can be interpreted as a classical instability that becomes relevant below some momentum scale in terms of matter density perturbations. We also consider the effect of the background evolution influenced by matter on the stability of the gravity sector perturbations. In particular, we address the previous claims of ghost instability in the IR around the late time attractor. We show that, although the matter-induced modification of the evolution potentially brings tension to the stability conditions, one goes beyond the regime of validity of the effective theory well before the solutions become unstable. We also draw attention to the fact that the IR stability conditions are also enforced by the existence requirements of consistent background solutions.

We elaborate upon the model of baryogenesis from decaying magnetic helicity by focusing on the evolution of the baryon number and magnetic field through the Standard Model electroweak crossover. The baryon asymmetry is determined by a competition between the helical hypermagnetic field, which sources baryon number, and the electroweak sphaleron, which tends to wash out baryon number. At the electroweak crossover, both of these processes become inactive; the hypermagnetic field is converted into an electromagnetic field, which does not source baryon number, and the weak gauge boson masses grow, suppressing the electroweak sphaleron reaction. An accurate prediction of the relic baryon asymmetry requires a careful treatment of the crossover. We extend our previous study [K. Kamada and A. J. Long, Phys. Rev. D 94, 063501 (2016)], taking into account the gradual conversion of the hypermagnetic into the electromagnetic field. If the conversion is not completed by the time of sphaleron freeze-out, as both analytic and numerical studies suggest, the relic baryon asymmetry is enhanced compared to previous calculations. The observed baryon asymmetry of the Universe can be obtained for a primordial magnetic field that has a present-day field strength and coherence length of $B_0\sim {10}^{-17}\mathrm{G}$ and ${\lambda }_0\sim {10}^{-3}\mathrm{pc}$ and a positive helicity. For larger $B_0$ the baryon asymmetry is overproduced, which may be in conflict with blazar observations that provide evidence for an intergalactic magnetic field of strength $B_0\gtrsim {10}^{-14–16}\mathrm{G}$.

The H.E.S.S. Collaboration has reported a high-energy spherically symmetric diffuse $\gamma$-ray emission in the inner 50 pc of the Milky Way, up to $\sim 50\mathrm{TeV}$. Here, we propose a leptonic model which provides an alternative to the hadronic scenario presented by the H.E.S.S. Collaboration, and connects the newly reported TeV emission to the Fermi-LAT Galactic Center GeV excess. Our model relies on a combination of inverse Compton emission from a population of millisecond pulsars—which can account for the GeV excess—and a supermassive black hole-induced spike of heavy ($\sim 60\mathrm{TeV}$) dark matter particles annihilating into electrons with a subthermal cross section. With an up-to-date interstellar radiation field, as well as a standard magnetic field and diffusion setup, our model accounts for the spectral morphology of the detected emission. Moreover, we show that the dark matter-induced emission reproduces the spatial morphology of the H.E.S.S. signal above $\sim 10\mathrm{TeV}$, while we obtain a slightly more extended component from pulsars at lower energies, which could be used as a prediction for future H.E.S.S. observations.

The AMS-02 experiment has reported a new measurement of the antiproton/proton ratio in Galactic cosmic rays (CRs). In the energy range $E\sim 60–450\mathrm{GeV}$, this ratio is found to be remarkably constant. Using recent data on CR proton, helium, and carbon fluxes, ${}^{10}\mathrm{Be}/{}^9\mathrm{Be}$ and B/C ratios, we have performed a global Bayesian analysis based on a Markov chain Monte Carlo sampling algorithm under a “two halo model” of CR propagation. In this model, CRs are allowed to experience a different type of diffusion when they propagate in the region close to the Galactic disk. We found that the vertical extent of this region is about 900 pc above and below the disk, and the corresponding diffusion coefficient scales with energy as $D\propto E^{0.15}$, describing well the observations on primary CR spectra, secondary/primary ratios, and anisotropy. Under this model, we have carried out improved calculations of antiparticle spectra arising from secondary CR production and their corresponding uncertainties. We made use of Monte Carlo generators and accelerator data to assess the antiproton production cross sections and their uncertainties. While the positron excess requires the contribution of additional unknown sources, we found that the new AMS-02 antiproton data are consistent, within the estimated uncertainties, with our calculations based on secondary production.

Supersymmetric extensions of the standard model predict the existence of nontopological solitons, $Q$-balls. Assuming the standard cosmological history preceded by inflation, $Q$-balls can form in the early universe and can make up the dark matter. The relatively large masses of such dark-matter particles imply a low number density, making direct detection very challenging. The strongest limits come from the existence of neutron stars because, if a baryonic $Q$-ball is captured by a neutron star, the $Q$-ball can absorb the baryon number releasing energy and eventually destroying a neutron star. However, in the presence of baryon number violating higher-dimensional operators, the growth of a $Q$-ball inside a neutron star is hampered once the $Q$-ball reaches a certain size. We reexamine the limits and identify some classes of higher-dimensional operators for which supersymmetric $Q$-balls can account for dark matter. The present limits leave a wide range of parameters available for dark matter in the form of supersymmetric $Q$-balls.

All-sky searches for gravitational-wave pulsars are generally limited in sensitivity by the finite availability of computing resources. Semicoherent searches are a common method of maximizing search sensitivity given a fixed computing budget. The work of Wette and Prix [Phys. Rev. D 88, 123005 (2013)] and Wette [Phys. Rev. D 92, 082003 (2015)] developed a semicoherent search method which uses metrics to construct the banks of pulsar signal templates needed to search the parameter space of interest. In this work we extend the range of validity of the parameter-space metrics using an empirically derived relationship between the resolution (or mismatch) of the template banks and the mismatch of the overall search. This work has important consequences for the optimization of metric-based semicoherent searches at fixed computing cost.

Lepton mass effects play a decisive role in the description of elastic lepton-proton scattering when the beam’s energy is comparable to the mass of the lepton. The future Muon Scattering Experiment (MUSE) experiment, which is devised to solve the “Proton Radius Puzzle,” is going to cover the corresponding kinematic region for a scattering of muons by a proton target. We anticipate that helicity-flip meson exchanges will make a difference in the comparison of elastic electron-proton vs muon-proton scattering in MUSE. In this article, we estimate the $\sigma$ meson exchange contribution in the $t$ channel. This contribution, mediated by two-photon coupling of $\sigma$, is calculated to be at most $\sim 0.1\%$ for muons in the kinematics of MUSE, and it appears to be about 3 orders of magnitude larger than for electrons because of the lepton-mass difference.

We apply a nonperturbative soft-wall AdS/QCD approach to the description of deuteron structure functions and tensor polarized properties. Present work is a completion of our previous study on electromagnetic form factors. By the appropriate choice of two couplings in the effective action we are able to reproduce both the form factors and structure functions in full consistency with model-independent constraints set by perturbative QCD. Our framework is based on a five-dimensional action in AdS space formulated in terms of vector fields dual to the deuteron and the electromagnetic fields. The AdS fields depend on four Minkowski and one holographic coordinate $z$. The scale dependence of the form factors and structure functions is consistent with quark counting rules implying the $1/Q^{10}$ behavior of the charge form factor $G_C(Q^2)$, structure functions $A(Q^2)$ and $B(Q^2)$, and the $1/Q^{12}$ behavior of the magnetic $G_M(Q^2)$ and quadrupole $G_Q(Q^2)$ form factors.

We discuss the equivalence between light-front time-ordered-perturbation theory and covariant quantum field theory in light-front quantization, in the case of quantum electrodynamics at one-loop level. In particular, we review the one-loop calculation of the vertex correction, fermion self-energy and vacuum polarization. We apply the procedure of integration by residue over the light-front energy in the loop to show how the perturbative expansion in covariant terms can be reduced to a sum of propagating and instantaneous diagrams of light-front time-ordered perturbation theory. The detailed proof of equivalence between the two formulations of the theory resolves the controversial question on which form should be used for the gauge-field propagator in the light-cone gauge in the covariant approach.

We derive the gauge covariance requirement imposed on the QED fermion-photon three-point function within the framework of a spectral representation for fermion propagators. When satisfied, such requirement ensures solutions to the fermion propagator Schwinger-Dyson equation (SDE) in any covariant gauge with arbitrary numbers of spacetime dimensions to be consistent with the Landau-Khalatnikov-Fradkin transformation (LKFT). The general result has been verified by the special cases of three and four dimensions. Additionally, we present the condition that ensures the vacuum polarization is independent of the gauge parameter. As an illustration, we show how the gauge technique dimensionally regularized in four dimensions does not satisfy the covariance requirement.

In the supersymmetric scenario known as mirage mediation (MM), the soft supersymmetry (SUSY) breaking terms receive comparable anomaly-mediation and moduli-mediation contributions leading to the phenomenon of mirage unification. The simplest MM SUSY breaking models which are consistent with the measured Higgs mass and sparticle mass constraints are strongly disfavored by fine-tuning considerations. However, while MM makes robust predictions for gaugino masses, the scalar sector is quite sensitive to specific mechanisms for moduli stabilization and potential uplifting. We suggest here a broader setup of generalized mirage mediation (GMM), where heretofore discrete parameters are allowed as continuous to better parametrize these other schemes. We find that natural SUSY spectra consistent with both the measured value of $m_h$ as well as LHC lower bounds on superpartner masses are then possible. We explicitly show that models generated from natural GMM may be beyond the reach of even high-luminosity LHC searches. In such a case, the proposed International Linear $e^{+}{e}^{-}$ Collider will be required for natural SUSY discovery via higgsino pair production reactions. We also outline prospects for detection of higgsino-like WIMPs from natural GMM.

It is often argued that the minimal supersymmetric standard model has $O(100)$ free parameters, and the generic parameter region is already excluded by the null observation of the flavor and $CP$-violating processes as well as the constraints from the LHC experiments. This situation naturally leads us to consider the case where all the dangerous soft supersymmetry breaking terms, such as the scalar masses and scalar couplings, are absent, while only the unified gaugino mass term and the $\mu$ term are nonvanishing at the grand unification scale. We revisit this simple situation taking into account the observed Higgs boson mass, 125 GeV. Since the gaugino mass and the $\mu$ term are fixed in order to explain the Higgs boson and the $Z$ boson masses, there is no free parameter left in this scenario. We find that there are three independent parameter sets that exist including ones which have not been discussed in the literature. We also find that the abundance of the dark matter can be explained by relic gravitinos which are nonthermally produced as decay products of the supersymmetry particles while satisfying constraints from big bang nucleosynthesis. We discuss the effects of the gravity mediation which generically gives a contribution to the soft terms of the order of the gravitino mass. It turns out that a newly found parameter set is preferable to explain the Higgs boson mass as well as the gravitino dark matter while satisfying the constraints from the electric dipole moments of the electron and the nucleon.