The Starobinsky model of modified gravity suggested to explain dark energy may also be considered in the astrophysical context. Recently it has been pointed out that in contracting regions curvature oscillations around the general relativity (GR) value may lead to the production of high energy particles that contribute to the cosmic ray flux. We revisit these calculations in the Einstein frame and show that the continuous approximation for the matter density used in the original calculations is not valid. We show that this problem is generic in $F(R)$-gravity models introduced to describe the dark energy. We go beyond the approximation and find the rate of particle production to be negligible.

High frequency quasiperiodic oscillations (HF QPOs) detected in the power spectra of low mass x-ray binaries (LMXBs) could unveil the fingerprints of gravitation in the strong field regime. Using the energy-momentum relation we calculate the energy a clump of plasma orbiting in the accretion disk releases during circularization of its slightly eccentric relativistic orbit. Following previous works, we highlight the strong tidal force as a mechanism to dissipate such energy. We show that tides acting on the clump are able to reproduce the observed coherence of the upper HF QPO seen in LMXBs with a neutron star (NS). The quantity of energy released by the clump and relativistic boosting might give a modulation amplitude in agreement with that observed in the upper HF QPO. Both the amplitude and coherence of the upper HF QPO in NS LMXBs could allow us to disclose, for the first time, the tidal circularization of relativistic orbits occurring around a neutron star.

We compute the fluxes of radio photons from conversion of axionlike particle dark matter in cosmic magnetic fields. We find that for axionlike particle masses around ${10}^{-6}\mathrm{eV}$ and effective coupling constants to photons $g_{a\gamma }\gtrsim {10}^{-13}{\mathrm{GeV}}^{-1}$ strongly magnetized nearby stellar winds may give detectable linelike radio photon signals, although predicted fluxes are highly uncertain due to the poorly known structure of the magnetic fields. Nevertheless, it may be worth while to conduct a dedicated search in the direction of such sources. When combined with a possible future laboratory detection of axionlike dark matter such observations may in turn provide information on the small scale magnetic field structure in such objects.

Factorization of scattering is the hallmark of integrable $1+1$ dimensional quantum field theories. For factorization of scattering to be possible the set of masses and momenta must be conserved in any two-to-two scattering process. We use this fact to constrain the form of the Ramond-Ramond fluxes for integrable supergravity anti–de Sitter (AdS) backgrounds by analyzing tree-level scattering of two AdS bosons into two fermions on the worldsheet of a Berenstein-Maldacena-Nastase string. We find a condition which can be efficiently used to rule out integrability of AdS strings and therefore of the corresponding AdS/conformal field theory dualities, as we demonstrate for some simple examples.

The quenched gluon and ghost propagator data published in [Duarte et al. Phys. Rev. D 94, 014502 (2016).] is reanalyzed following the suggestion of [Boucaud et al. Phys. Rev. D 96, 098501 (2017).] to resolve the differences between the infrared data of the simulations. Our results confirm that the procedure works well either for the gluon or for the ghost propagator but not for both propagators simultaneously as the observed deviations in the data follow opposite patterns. Definitive conclusions require improving the determination of the (ratios) of lattice spacings. A simple procedure for the relative calibration of the lattice spacing in lattice simulations is suggested.

The authors of [Phys. Rev. D 94, 014502 (2016)] reported about a careful analysis of the impact of lattice artifacts on the $SU(3)$ gauge-field propagators. In particular, they found that the low-momentum behavior of the renormalized propagators depends on the lattice bare coupling and interpreted this as the result of its being affected by discretization artifacts. We discuss here a different interpretation for these results.

This paper presents a new method of numerical computation of the mass-independent QED contributions to the electron anomalous magnetic moment which arise from Feynman graphs without closed electron loops. The method is based on a forestlike subtraction formula that removes all ultraviolet and infrared divergences in each Feynman graph before integration in Feynman-parametric space. The integration is performed by an importance sampling Monte-Carlo algorithm with the probability density function that is constructed for each Feynman graph individually. The method is fully automated at any order of the perturbation series. The results of applying the method to 2-loop, 3-loop, 4-loop Feynman graphs, and to some individual 5-loop graphs are presented, as well as the comparison of this method with other ones with respect to Monte Carlo convergence speed.

We assess the applicability of the Wigner function formulation in its present form to the chiral magnetic effect and note some issues regarding the conservation and the consistency of the electric current in the presence of an inhomogeneous and time-dependent axial chemical potential. The problems are rooted in the ultraviolet divergence of the underlying field theory associated with the axial anomaly and can be fixed with the Pauli-Villars regularization of the Wigner function. The chiral magnetic current with a nonconstant axial chemical potential is calculated with the regularized Wigner function and the phenomenological implications are discussed.

We propose a model to explain the tiny masses of neutrinos with lepton number conservation, where neither too heavy particles beyond the TeV-scale nor tiny coupling constants are required. Assignments of conserving lepton numbers to new fields result in an unbroken $Z_2$ symmetry that stabilizes the dark matter candidate (the lightest $Z_2$-odd particle). In this model, $Z_2$-odd particles play an important role in generating the masses of neutrinos. The scalar dark matter in our model can satisfy constraints on the dark matter abundance and those from direct searches. It is also shown that the strongly first-order phase transition, which is required for electroweak baryogenesis, can be realized in our model. In addition, the scalar potential can in principle contain $CP$-violating phases, which can also be utilized for baryogenesis. Therefore, three problems in the standard model—namely, the absence of neutrino masses, the dark matter candidate, and the mechanism to generate the baryon asymmetry of the Universe—may be simultaneously resolved at the TeV scale. The phenomenology of this model is also discussed briefly.

$L_{\mu }-L_{\tau }$ gauge boson ($Z^{\prime }$) with a mass in the MeV to GeV region can resolve not only the muon $g-2$ excess, but also the gap in the high-energy cosmic neutrino spectrum at IceCube. It was recently proposed that such a light gauge boson can be detected during the Belle II experiment with a luminosity of $50{\mathrm{ab}}^{-1}$ by the $e^{+}{e}^{-}\to \gamma +\cancel{E}$ process through the kinetic mixing with the photon, where the missing energy $\cancel{E}$ is from the $Z^{\prime }\to \overline{\nu }\nu$ decays. We study the phenomenological implications when a pair of singlet vectorlike leptons carrying different $L_{\mu }-L_{\tau }$ charges are included, and a complex singlet scalar (${\varphi }_S$) is introduced to accomplish the spontaneous $U(1{)}_{L_{\mu }-L_{\tau }}$ symmetry breaking. It is found that the extension leads to several phenomena of interest, including (i) branching ratio (BR) for $h\to \mu \tau$ can be of the order of ${10}^{-3}$; (ii) ${\varphi }_S$-mediated muon $g-2$ can be of the order of $10\times {10}^{-10}$; (iii) BR for $\tau \to \mu {\varphi }_S^{*}\to \mu Z^{\prime }{Z}^{\prime }$ can be ${10}^{-8}$, and (iv) kinetic mixing between the $Z^{\prime }$ boson and photon is sensitive to the relative heavy lepton masses. The predicted BRs for $\tau \to (3\mu +\cancel{E},5\mu )$ through the leptonic $Z^{\prime }$ decays can reach a level of ${10}^{-9}$, in which the results fall within the sensitivity of the Belle II in the search for the rare tau decays.

Dark photons in the MeV to GeV mass range are important targets for experimental searches. We consider the case where dark photons $A^{\prime }$ decay invisibly to hidden dark matter $X$ through $A^{\prime }\to XX$. For generic masses, proposed accelerator searches are projected to probe the thermal target region of parameter space, where the $X$ particles annihilate through $XX\to A^{\prime }\to \mathrm{SM}$ in the early universe and freeze out with the correct relic density. However, if $m_{A^{\prime }}\approx 2m_X$, dark matter annihilation is resonantly enhanced, shifting the thermal target region to weaker couplings. For $\sim 10\%$ degeneracies, we find that the annihilation cross section is generically enhanced by 4 (2) orders of magnitude for scalar (pseudo-Dirac) dark matter. For such moderate degeneracies, the thermal target region drops to weak couplings beyond the reach of all proposed accelerator experiments in the scalar case and becomes extremely challenging in the pseudo-Dirac case. Proposed direct detection experiments can probe moderate degeneracies in the scalar case. For greater degeneracies, the effect of the resonance can be even more significant, and both scalar and pseudo-Dirac cases are beyond the reach of all proposed accelerator and direct detection experiments. For scalar dark matter, we find an absolute minimum that sets the ultimate experimental sensitivity required to probe the entire thermal target parameter space, but for pseudo-Dirac fermions, we find no such thermal target floor.

We perform a simulation on the DUNE experiment to probe the capability of future neutrino long-baseline experiments to constrain the parameter space of high-energy models by using the correlation between the atmospheric and reactor mixing angles. As an example, we analyze the tetrahedral flavor symmetry model, which predicts a strong relation between the nonzero value of ${\theta }_{13}$ and a deviation of ${\theta }_{23}$ from maximality. We show that in this case, the model can realistically be excluded by more than $3\sigma$ for most of the parameter space. We also study the octant degeneracy at DUNE and its impact on the sensitivity of such models.

We propose a new search for dark matter at the LHC, characteristic of scenarios beyond the Standard Model with a pseudoscalar portal between the visible and dark sectors. This search, leading to a $\overline{b}bZ(\to \ell \ell )+{\cancel{E}}_T$ final state, reaches large regions of parameter space not probed by dark matter searches via $\mathrm{multijet}+{\cancel{E}}_T$, searches for new scalars and flavor bounds. We show that this search could be used to test the dark matter origin of the gamma-ray Galactic Center excess with LHC Run 2 data.

We consider a feeble repulsive interaction between ordinary matter and dark matter, with a range similar to or larger than the size of the Earth. Dark matter can thus be repelled from the Earth, leading to null results in direct detection experiments, regardless of the strength of the short-distance interactions of dark matter with atoms. Generically, such a repulsive force would not allow trapping of dark matter inside astronomical bodies. In this scenario, accelerator-based experiments may furnish the only robust signals of asymmetric dark matter models, which typically lack indirect signals from self-annihilation. Some of the variants of our hypothesis are also briefly discussed.

We study quantitatively the importance of the recently derived next-to-leading-order corrections to the deep inelastic scattering structure functions at small $x$ in the dipole formalism. We show that these corrections can be significant and depend on the factorization scheme used to resum large logarithms of energy into renormalization group evolution with the Balitsky-Kovchegov equation. This feature is similar to what has recently been observed for single inclusive forward hadron production. Using a factorization scheme consistent with the one recently proposed for the single inclusive cross section, we show that it is possible to obtain meaningful results for the deep inelastic scattering cross sections.

Inspired by the recently observed ${\mathrm{\Omega }}_c^0$ states at LHCb, we decode their properties by performing an analysis of their mass spectrum and decay behavior. Our studies show that the five narrow states, i.e., ${\mathrm{\Omega }}_c(3000{)}^0$, ${\mathrm{\Omega }}_c(3050{)}^0$, ${\mathrm{\Omega }}_c(3066{)}^0$, ${\mathrm{\Omega }}_c(3090{)}^0$, and ${\mathrm{\Omega }}_c(3119{)}^0$, could be grouped into the $1P$ states with negative parity. Among them, the ${\mathrm{\Omega }}_c(3000{)}^0$ and ${\mathrm{\Omega }}_c(3090{)}^0$ states could be the $J^P=1/2^{-}$ candidates, while ${\mathrm{\Omega }}_c(3050{)}^0$ and ${\mathrm{\Omega }}_c(3119{)}^0$ are suggested as the $J^P=3/2^{-}$ states. ${\mathrm{\Omega }}_c(3066{)}^0$ could be regarded as a $J^P=5/2^{-}$ state. Since the spin-parity, electromagnetic transitions, and possible hadronic decay channels ${\mathrm{\Omega }}_c^{(*)}\pi$ have not been measured yet, other explanations are also probable for these narrow ${\mathrm{\Omega }}_c^0$ states. Additionally, we discuss the possibility of the broad structure ${\mathrm{\Omega }}_c(3188{)}^0$ as a $2S$ state with $J^P=1/2^{+}$ or $J^P=3/2^{+}$. In our scheme, ${\mathrm{\Omega }}_c(3119{)}^0$ cannot be a $2S$ candidate.

Two independent criteria are presented that together guarantee exponential suppression of the two-loop cosmological constant in nonsupersymmetric heterotic strings. They are derived by performing calculations in both the full string theory and in its effective field theory, and come respectively from contributions that involve only physical untwisted states, and contributions that include orbifold twisted states. The criteria depend purely on the spectrum and charges, so a model that satisfies them will do so with no fine-tuning. An additional consistency condition (emerging from the so-called separating degeneration limit of the two-loop diagram) is that the one-loop cosmological constant must also be suppressed, by Bose-Fermi degeneracy in the massless spectrum. We comment on the effects of the residual exponentially suppressed one-loop dilaton tadpole, with the conclusion that the remaining instability would be under perturbative control in a generic phenomenological construction. We remark that theories of this kind, that have continued exponential suppression to higher orders, can form the basis for a string implementation of the “naturalness without supersymmetry” idea.

We study the butterfly effect by considering shock wave solutions near the horizon of the anti–de Sitter black hole in some three-dimensional gravity models including 3D Einstein gravity, minimal massive 3D gravity, new massive gravity, generalized massive gravity, Born-Infeld 3D gravity, and new bigravity. We calculate the butterfly velocities of these models and also we consider the critical points and different limits in some of these models. By studying the butterfly effect in the generalized massive gravity, we observe a correspondence between the butterfly velocities and right-left moving degrees of freedom or the central charges of the dual 2D conformal field theories.

Semiholographic models of non-Fermi liquids have been shown to have generically stable generalized quasiparticles on the Fermi surface. Although these excitations are broad and exhibit particle-hole asymmetry, they were argued to be stable from interactions at the Fermi surface. In this work, we use this observation to compute the density response and collective behaviour in these systems. Compared to the Fermi liquid case, we find that the boundaries of the particle-hole continuum are blurred by incoherent contributions. However, there is a region inside this continuum, that we call inner core, within which salient features of the Fermi liquid case are preserved. A particularly striking prediction of our work is that these systems support a plasmonic collective excitation which is well-defined at large momenta, has an approximately linear dispersion relation and is located in the low-energy tail of the particle-hole continuum. Furthermore, the dynamic screening potential shows deep attractive regions as a function of the distance at higher frequencies which might lead to long-lived pair formation depending on the behavior of the pair susceptibility. We also find that Friedel oscillations are present in these systems but are highly suppressed.