As an attempt to solve the black hole information loss paradox, recently there has been the suggestion that, due to semiclassical effects, a pre-Hawking radiation must exist during the gravitational collapse of matter, which in turn prevents the apparent horizon from forming. Assuming the pre-Hawking radiation does exist, here we argue the opposite. First we note that the stress energy tensor near the horizon for the pre-Hawking radiation is far too small to do anything to the motion of a collapsing shell. Thus the shell will always cross the apparent horizon within a finite proper time. Moreover, the amount of energy that can be radiated must be less than half of the total initial energy (if the particle starts at rest at infinity) before the shell becomes a null shell and cannot radiate any more without becoming tachyonic. We conclude that for any gravitational collapsing process within Einstein gravity and semiclassical quantum field theory, the formation of the apparent horizon is inevitable. Pre-Hawking radiation is therefore not a valid solution to the information paradox.

It is known that the perturbative instability of tensor excitations in higher derivative gravity may not take place if the initial frequency of the gravitational waves is below the Planck threshold. One can assume that this is a natural requirement if the cosmological background is sufficiently mild, since in this case the situation is qualitatively close to the free gravitational wave in flat space. Here, we explore the opposite situation and consider the effect of a very far from Minkowski radiation-dominated or de Sitter cosmological background with a large Hubble rate, e.g., typical of an inflationary period. It turns out that, then, for initial Planckian or even trans-Planckian frequencies, the instability is rapidly suppressed by the very fast expansion of the Universe.

We study the existence and stability of isoperimetric surfaces in a family of rotating black holes in new massive gravity. We show that the stability of such surfaces is determined by the sign of the hair parameter. We use the isoperimetric surfaces to find a geometric inequality between the area and the angular momentum of the black hole, conjecturing geometric inequalities for more general black holes.

We generalize the action for point particle motion to a double field theory background. After deriving the general equations of motion for these particle geodesics, we specialize to the case of a cosmological background with vanishing antisymmetric tensor field. We then show that the geodesics can be extended to infinity in both time directions once we define the appropriate physical clock. Following this prescription, we also show the existence of a singularity-free cosmological solution.

The left-right symmetric model (LRSM) is an attractive extension of the Standard Model (SM) that can address the origin of parity violation in the SM electroweak interactions, generate tiny neutrino masses, accommodate dark matter (DM) candidates, and provide a natural framework for baryogenesis through leptogenesis. In this work, we utilize the minimal LRSM to study the recently reported DAMPE results of the cosmic $e^{+}{e}^{-}$ spectrum, which exhibits a tentative peak around 1.4 TeV, while satisfying the current neutrino data. We propose to explain the DAMPE peak with a complex scalar DM $\chi$ in two scenarios: (1) $\chi {\chi }^{*}\to H_1^{++}{H}_1^{--}\to {\ell }_i^{+}{\ell }_i^{+}{\ell }_j^{-}{\ell }_j^{-}$, and (2) $\chi {\chi }^{*}\to H_k^{++}{H}_k^{--}\to {\ell }_i^{+}{\ell }_i^{+}{\ell }_j^{-}{\ell }_j^{-}$ accompanied by $\chi {\chi }^{*}\to H_1^{+}{H}_1^{-}\to {\ell }_i^{+}{\nu }_{{\ell }_i}{\ell }_j^{-}{\nu }_{{\ell }_j}$, with ${\ell }_{i,j}=e$, $\mu$, $\tau$ and $k=1$, 2. We fit the theoretical prediction of the $e^{+}{e}^{-}$ spectrum to relevant experimental data to determine the scalar mass spectrum favored by the DAMPE excess. We also consider various constraints from theoretical principles and collider experiments, as well as DM relic density and direct search experiments. We find that there is ample parameter space to interpret the DAMPE data while also passing the constraints. On the other hand, our explanations usually imply the existence of other new physics at an energy scale ranging from ${10}^7$ to ${10}^{11}\mathrm{GeV}$. Collider tests of our explanations are also discussed.

Slightly extending a right-handed neutrino version of the $3-3-1$ model, we show that it is not only possible to solve the strong $CP$ problem but also to give the total dark matter abundance reported by the Planck collaboration. Specifically, we consider the possibility of introducing a $3-3-1$ scalar singlet to implement a gravity stable Peccei-Quinn mechanism in this model. Remarkably, for allowed regions of the parameter space, the arising axions with masses $m_a\approx \mathrm{meV}$ can both make up the total dark matter relic density through nonthermal production mechanisms and be very close to the region to be explored by the IAXO helioscope.

Density changes in the atmosphere produce a fluctuating gravity field that affects gravity strainmeters or gravity gradiometers used for the detection of gravitational waves and for geophysical applications. This work addresses the impact of the atmospheric local gravity noise on such detectors, extending previous analyses. In particular we present the effect introduced by the building housing the detectors, and we analyze local gravity-noise suppression by constructing the detector underground. We present also new sound spectra and correlation measurements. The results obtained are important for the design of future gravitational-wave detectors and gravity gradiometers used to detect prompt gravity perturbations from earthquakes.

Volkov states and Volkov propagator are the basic analytical tools to investigate QED processes occurring in the presence of an intense plane-wave electromagnetic field. In the present paper we provide alternative and relatively simple proofs of the completeness and of the orthonormality at a fixed time of the Volkov states. Concerning the completeness, we exploit some known properties of the Green’s function of the Dirac operator in a plane wave, whereas the orthonormality of the Volkov states is proved, relying only on a geometric argument based on the Gauss theorem in four dimensions. In relation with the completeness of the Volkov states, we also study some analytical properties of the Green’s function of the Dirac operator in a plane wave, which we explicitly prove to coincide with the Volkov propagator in configuration space. In particular, a closed-form expression in terms of modified Bessel functions and Hankel functions is derived by means of the operator technique in a plane wave and different asymptotic forms are determined. Finally, the transformation properties of the Volkov propagator under general gauge transformations and a general gauge-invariant expression of the so-called dressed mass in configuration space are presented.

We analyze the charged lepton flavor violating (CLFV) decays of vector mesons $V\to l_i^{\pm }{l}_j^{\mp }$ with $V\in \{\varphi ,J/\mathrm{\Psi },\mathrm{\Upsilon },{\rho }^0,\omega \}$ in the BLMSSM model. This new model is introduced as a supersymmetric extension of the Standard Model (SM), where local gauged baryon number $B$ and lepton number $L$ are considered. The numerical results indicate the BLMSSM model can produce significant contributions to such two-body CLFV decays, and the branching ratios to these CLFV processes can easily reach the present experimental upper bounds. Therefore, searching for CLFV processes of vector mesons may be an effective channel to study new physics.

We perform a detailed study of inclusive jet production cross sections at the LHC and compare the QCD theory predictions based on the recently developed formalism for threshold and jet radius joint resummation at next-to-leading logarithmic accuracy to inclusive jet data collected by the CMS Collaboration at $\sqrt{S}=7$ and 13 TeV. We compute the cross sections at next-to-leading order in QCD with and without the joint resummation for different choices of jet radii $R$ and observe that the joint resummation leads to crucial improvements in the description of the data. Comprehensive studies with different parton distribution functions demonstrate the necessity of considering the joint resummation in fits of those functions based on the LHC jet data.

We present a Pisarski-Wilczek stability analysis of SU(4) gauge theory coupled simultaneously to fermions charged under the fundamental and two-index antisymmetric representations of the gauge group. We carry out the calculation to one loop in the $\epsilon$ expansion, assuming that the two species of fermion undergo a simultaneous chiral transition. The results indicate that the chiral transition is first order.

We investigate several examples of Yang-Mills gauge configurations containing center vortex structures, including intersection points between vortices and nontrivial color structures residing on the vortex world surfaces. Various topological charge contributions of the color structures and intersection points are studied in these configurations. Low-lying eigenmodes of the (overlap) Dirac operator in the presence of these vortex backgrounds are analyzed. The results indicate characteristic properties for spontaneous chiral symmetry breaking.

In this paper the phase structure of dense quark matter has been investigated at zero temperature in the presence of baryon, isospin and chiral isospin chemical potentials in the framework of massless ($3+1$)-dimensional Nambu–Jona-Lasinio model with two quark flavors. It has been shown that in the large-$N_c$ limit ($N_c$ is the number of colors of quarks) there exists a duality correspondence between the chiral symmetry breaking phase and the charged pion condensation one. The key conclusion of our studies is the fact that chiral isospin chemical potential generates charged pion condensation in dense quark matter with isotopic asymmetry.

We study the influence of a background magnetic field on the $J/\psi$ vector meson in a Dirac-Born-Infeld-extension of the soft wall model, building upon our earlier work [Phys. Rev. D 91, 086002 (2015)]. In this specific holographic QCD model, we discuss the heavy quark number susceptibility and diffusion constants of charm quarks and their dependence on the magnetic field by either a hydrodynamic expansion or by numerically solving the differential equation. This allows us to determine the response of these transport coefficients to the magnetic field. The effects of the latter are considered both from a direct as indirect (medium) viewpoint. As expected, we find a magnetic field induced anisotropic diffusion, with a stronger diffusion in the longitudinal direction compared to the transversal one. We backup, at least qualitatively, our findings with a hanging string analysis of heavy quark diffusion in a magnetic field. From the quark number susceptibility we can extract an estimate for the effective deconfinement temperature in the heavy quark sector, reporting consistency with the phenomenon of inverse magnetic catalysis.

We study the time evolution of the early Universe, which is developed by a cosmological constant ${\mathrm{\Lambda }}_4$ and supersymmetric Yang-Mills (SYM) fields in the Friedmann-Robertson-Walker space-time. The renormalized vacuum expectation value of the energy-momentum tensor of the SYM theory is obtained in a holographic way. It includes a radiation of the SYM field, parametrized as $C$. The evolution is controlled by this radiation $C$ and the cosmological constant ${\mathrm{\Lambda }}_4$. For positive ${\mathrm{\Lambda }}_4$, an inflationary solution is obtained at late time. When $C$ is added, the quantum mechanical situation at early time is fairly changed. Here we perform the early time analysis in terms of two different approaches, (i) the Wheeler-DeWitt equation and (ii) Lorentzian path integral with the Picard-Lefschetz method by introducing an effective action. The results of two methods are compared.

Starting from the $48+48$ component multiplet of supercurrents for a rigid $N=2$ tensor multiplet in four spacetime dimensions, we obtain the transformation of the linearized supergravity multiplet which couples to this supercurrent multiplet. At the linearized level, this $48+48$ component supergravity multiplet decouples into the $24+24$ component linearized standard Weyl multiplet and a $24+24$ component irreducible matter multiplet containing a real scalar field. By a consistent application of the supersymmetry algebra with field-dependent structure constants appropriate to $N=2$ conformal supergravity, we find the full transformation law for this multiplet in a conformal supergravity background. By performing a suitable field redefinition, we find that the multiplet is a generalization of the flat space multiplet, obtained by Howe et al. in Nucl. Phys. B214, 519 (1983), to a conformal supergravity background. We also present a set of constraints which can be consistently imposed on this multiplet to obtain a restricted minimal $8+8$ off-shell matter multiplet. We also show, as an example, the precise embedding of the tensor multiplet inside this multiplet.

In this paper, we derive the general leading-order classical Lagrangian covering all fermion operators of the nonminimal standard-model extension (SME). Such a Lagrangian is considered to be the point-particle analog of the effective field theory description of Lorentz violation that is provided by the SME. At leading order in Lorentz violation, the Lagrangian obtained satisfies the set of five nonlinear equations that govern the map from the field theory to the classical description. This result can be of use for phenomenological studies of classical bodies in gravitational fields.

Periodic spatial modulations arise in analogue gravity experiments aimed at detecting the analogue version of the Hawking effect in a white-hole flow. Having the same spatial periodicity as low-frequency dispersive modes, they can induce resonances which significantly modify the scattering coefficients. This has been shown numerically in a previous work [X. Busch et al., Phys. Rev. D 90, 105005 (2014)], but the precise dependence of the low-frequency effective temperature on the amplitude and length of the undulation remains elusive. In this article, using the Korteweg–de Vries equation, we explicitly compute this dependence in the small-amplitude limit and find three regimes of “short,” “intermediate” and “long” undulations showing different scaling laws. In the latter, the effective temperature is completely determined by the properties of the undulation, independently of the surface gravity of the analogue white-hole flow. These results are extended to a more realistic hydrodynamical model in an Appendix C.

Observations of gravitational waves from inspiralling neutron star binaries—such as GW170817—can be used to constrain the nuclear equation of state by placing bounds on stellar tidal deformability. For slowly rotating neutron stars, the response to a weak quadrupolar tidal field is characterized by four internal-structure-dependent constants called “Love numbers.” The tidal Love numbers $k_2^{\mathrm{el}}$ and $k_2^{\mathrm{mag}}$ measure the tides raised by the gravitoelectric and gravitomagnetic components of the applied field, and the rotational-tidal Love numbers ${\mathfrak{f}}^{\mathrm{o}}$ and ${\mathfrak{k}}^{\mathrm{o}}$ measure those raised by couplings between the applied field and the neutron star spin. In this work, we compute these four Love numbers for perfect fluid neutron stars with realistic equations of state. We discover (nearly) equation-of-state independent relations between the rotational-tidal Love numbers and the moment of inertia, thereby extending the scope of I-Love-Q universality. We find that similar relations hold among the tidal and rotational-tidal Love numbers. These relations extend the applications of I-Love universality in gravitational-wave astronomy. As our findings differ from those reported in the literature, we derive general formulas for the rotational-tidal Love numbers in post-Newtonian theory and confirm numerically that they agree with our general-relativistic computations in the weak-field limit.