Considering the Lagrangian of the logarithmic nonlinear electrodynamics in the presence of a scalar dilaton field, we obtain a new class of topological black hole solutions of Einstein-dilaton gravity with two Liouville-type dilaton potentials. Black hole horizons and cosmological horizons, in these spacetimes, can be a two-dimensional positive, zero, or negative constant curvature surface. We find that the behavior of the electric field crucially depends on the dilaton coupling constant $\alpha$. For small $\alpha$, the electric field diverges near the origin, although its divergency is weaker than the linear Maxwell field. However, with increasing $\alpha$, the behavior of the electric field, near the origin, approaches to that of the Maxwell field. We also study casual structure, asymptotic behavior, and physical properties of the solutions. We find that, depending on the model parameters, the topological dilaton black holes may have one or two horizons, and even in some cases we encounter a naked singularity without horizon. We compute the conserved and thermodynamic quantities of the spacetime and investigate that these quantities satisfy the first law of thermodynamics. We also probe thermal stability in the canonical and grand canonical ensembles and disclose the effects of the dilaton field as well as nonlinear parameter on the thermal stability of the solutions. Finally, we investigate thermodynamical geometry of the obtained solutions by introducing a new metric and studying the phase transition points due to the divergency of the Ricci scalar. We find that the dilaton field affects the phase transition points of the system.

We introduce a classification scheme of the postmerger dynamics and gravitational wave emission in binary neutron star mergers, after identifying a new mechanism by which a secondary peak in the gravitational wave spectrum is produced. It is caused by a spiral deformation, the pattern of which rotates slower with respect to the double-core structure in the center of the remnant. This secondary peak is typically well separated in frequency from the secondary peak produced by a nonlinear interaction between a quadrupole and a quasiradial oscillation. The new mechanism allows for an explanation of low-frequency modulations seen in a number of physical characteristics of the remnant, such as the central lapse function, the maximum density and the separation between the two cores, but also in the gravitational wave amplitude. We find empirical relations for both types of secondary peaks between their gravitational wave frequency and the compactness of nonrotating individual neutron stars, that exist for fixed total binary masses. These findings are derived for equal-mass binaries without intrinsic neutron star spin analyzing hydrodynamical simulations without magnetic field effects. Our classification scheme may form the basis for the construction of detailed gravitational wave templates of the postmerger phase. We find that the quasiradial oscillation frequency of the remnant decreases with the total binary mass. For a given merger event, our classification scheme may allow one to determine the proximity of the measured total binary mass to the threshold mass for prompt black hole formation, which can, in turn, yield an estimate of the maximum neutron star mass.

This paper studies jetlike electromagnetic configurations surrounding a slowly spinning black-hole immersed in a uniformly magnetized force-free plasma. In the first part of this paper, we present a family of stationary solutions that are jet capable. While these solutions all satisfy the force-free equations and the appropriate boundary conditions, our numerical experiments show a unique relaxed state starting from different initial data, and so one member of the family is likely preferred over the others. In the second part of this paper, we analyze the perturbations of this family of jetlike solutions, and show that the perturbative modes exhibit a similar split into the trapped and traveling categories previously found for perturbed Blandford-Znajek solutions. In the eikonal limit, the trapped modes can be identified with the fast magnetosonic waves in the force-free plasma and the traveling waves are essentially the Alfvén waves. Moreover, within the scope of our analysis, we have not seen signs of unstable modes at the light-crossing time scale of the system, within which the numerical relaxation process occurs. This observation disfavors mode instability as the selection mechanism for picking out a preferred solution. Consequently, our analytical study is unable to definitively select a particular solution out of the family to serve as the aforementioned preferred final state. This remains an interesting open problem.

Thanks to the Planck Collaboration, we know the value of the scalar spectral index of primordial fluctuations with unprecedented precision. In addition, the joint analysis of the data from Planck, BICEP2, and KEK has further constrained the value of the tensor-to-scalar ratio $r$ so that chaotic inflationary scenarios seem to be disfavored. Inspired by these results, we look for a model that yields a value of $r$ that is larger than the one predicted by the Starobinsky model but is still within the new constraints. We show that purely quadratic, renormalizable, and scale-invariant gravity, implemented by loop corrections, satisfies these requirements.

The ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ reaction affects not only the production of ${}^7\mathrm{Li}$ in big bang nucleosynthesis, but also the fluxes of ${}^7\mathrm{Be}$ and ${}^8\mathrm{B}$ neutrinos from the Sun. This double role is exploited here to constrain the former by the latter. A number of recent experiments on ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ provide precise cross section data at $E=0.5–1.0\mathrm{MeV}$ center-of-mass energies. However, there is a scarcity of precise data at big bang energies, 0.1–0.5 MeV, and below. This problem can be alleviated, based on precisely calibrated ${}^7\mathrm{Be}$ and ${}^8\mathrm{B}$ neutrino fluxes from the Sun that are now available, assuming the neutrino flavor oscillation framework to be correct. These fluxes and the standard solar model are used here to determine the ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ astrophysical $S$-factor at the solar Gamow peak, $S_{34}^{\nu }(23_{-5}^{+6}\mathrm{keV})=0.548\pm 0.054\mathrm{keV}\mathrm{b}$. This new data point is then included in a reevaluation of the ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ $S$-factor at big bang energies, following an approach recently developed for this reaction in the context of solar fusion studies. The reevaluated $S$-factor curve is then used to redetermine the ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ thermonuclear reaction rate at big bang energies. The predicted primordial lithium abundance is ${}^7\mathrm{Li}/\mathrm{H}=5.0\times {10}^{-10}$, far higher than the Spite plateau.

We examine quintessence models for dark energy in which the scalar field $\varphi$ evolves near the vicinity of a local maximum or minimum in the potential $V(\varphi )$, so that $V(\varphi )$ can be approximated by a quadratic function of $\varphi$ with no linear term. We generalize previous studies of this type by allowing the initial value of $d\varphi /dt$ to be nonzero. We derive an analytic approximation for $w(a)$ and show that it is in excellent agreement with numerical simulations for a variety of scalar field potentials having local minima or maxima. We derive an upper bound on the present-day value of $w$ as a function of the other model parameters and present representative limits on these models from observational data. This work represents a final generalization of previous studies using linear or quadratic approximations for $V(\varphi )$.

Several groups have analyzed the publicly available Fermi-LAT data and have reported a spatially extended $\gamma$ ray excess of around 1–3 GeV from the region surrounding the Galactic center that might originate from annihilation of dark-matter particles with a rest mass $m_{\chi }\sim 30-40\mathrm{GeV}$. In this work we examine the role of the diffuse galactic gamma-ray emission templates played in suppressing the GeV excess. For such a purpose, we adopt in total 128 background templates that were generated by Ackermann et al. [Astrophys. J. 750, 3 (2012)] in the study of the Fermi-LAT observations of the diffuse gamma-ray emission considering the effects of cosmic rays and the interstellar medium. The possible GeV excess, assumed to follow the spatial distribution of the prompt gamma rays produced in the annihilation of dark-matter particles taking a generalized Navarro-Frenk-White profile with an inner slope $\alpha =1.2$, has been analyzed in some regions of interest. The introduction of such an additional component centered at the Galactic center is found to have improved the goodness of fit to the data significantly in all background template models regardless of whether the excess spectrum is fixed or not. Our results thus suggest that the presence of a statistically significant GeV excess in the inner Galaxy is robust, though its spectrum depends on the diffuse galactic gamma-ray emission model adopted in the analysis. The possible physical origin of the GeV excess component is discussed and, in the dark-matter model, the annihilation cross section of such particles is evaluated.

We revisit the Gross-Neveu model with $N$ fermion flavors in $1+1$ dimensions and compute its phase diagram at finite temperature and chemical potential in the large-$N$ limit. To this end, we double the number of fermion degrees of freedom in a specific way which allows us to detect inhomogeneous phases in an efficient manner. We show analytically that this “fermion doubling trick” predicts correctly the position of the boundary between the chirally symmetric phase and the phase with broken chiral symmetry. Most importantly, we find that the emergence of an inhomogeneous ground state is predicted correctly. We critically analyze our approach based on this trick and discuss its applicability to other theories, such as fermionic models in higher dimensions, where it may be used to guide the search for inhomogeneous phases.

We explore the idea of accidental dark matter (aDM) stability in the scale invariant local $U(1{)}_{B-L}$ model, which is a theory for neutrino and at the same time radiatively breaks scale invariance via quantum mechanical dynamics in the $U(1{)}_{B-L}$ sector. A real singlet scalar can be accidental DM with an accidental $Z_2$, by virtue of both extended symmetries. A $U(1{)}_{B-L}$ charged complex scalar can also be a viable accidental DM due to an accidental (or remanent) $Z_3$. They can reproduce correct relic density via the annihilations through the conventional Higgs portal or dark Higgs portal. The dark Higgs portal scenario is in tension with the LHC bound on $Z_{B-L}$, and only heavy DM of a few TeVs can have correct relic density. In particular, DM may trigger classical scale invariance spontaneous breaking. The situation is relaxed significantly in the $Z_3$ case due to the effective semiannihilation mode, and then light DM can be accommodated easily. In addition, the $Z_3$ model can accommodate the GeV scale $\gamma$-ray excess from the Galactic center via semiannihilation into pseudo-Goldstone boson. The best fit is achieved at a DM about 52 GeV, with an annihilation cross section consistent with the thermal relic density. The invisible Higgs branching ratio is negligible because the Higgs portal quartic coupling is very small ${\lambda }_{h\varphi }\lesssim {10}^{-3}$.

SU(2) gauge theory with one Dirac flavor in the adjoint representation is investigated on a lattice. Initial results for the gluonic and mesonic spectrum, static potential from Wilson and Polyakov loops, and the anomalous dimension of the fermionic condensate from the Dirac mode number are presented. The results found are not consistent with conventional confining behavior, pointing instead tentatively towards a theory lying within or very near the onset of the conformal window, with the anomalous dimension of the fermionic condensate in the range $0.9\lesssim {\gamma }_{*}\lesssim 0.95$. The implications of our work for building a viable theory of strongly interacting dynamics beyond the standard model are discussed.

The gravitational form factors are related to the matrix elements of the energy-momentum tensor $T^{\mu \nu }$. Using the light front wave functions of the scalar quark-diquark model for a nucleon predicted by the soft-wall AdS/QCD, we calculate the flavor-dependent $A(Q^2)$, $B(Q^2)$ and $\overline{C}(Q^2)$ form factors. We also present all the matrix elements of the energy-momentum tensor in a transversely polarized state. Further, we evaluate the matrix element of the Pauli-Lubanski operator in this model and show that the intrinsic spin sum rule involves the form factor $\overline{C}$. The longitudinal momentum densities in the transverse impact parameter space are also discussed for both unpolarized and transversely polarized nucleons.

We use the twist dimensions of the operators underlying the dynamical behavior of exclusive production processes as a tool for determining the structure of exotic heavy-quark states such as the $Z_c^{+}(4430)$ tetraquark. The resulting counting rules predict distinctive falloffs of the cross sections in center-of-mass energy, thus distinguishing whether the tetraquarks are segregated into di-meson molecules, diquark-antidiquark pairs, or more democratically arranged four-quark states. In addition, we propose straightforward methods of experimentally producing additional exotic multiquark states.

We study the effect of intense magnetic fields on the phase diagram of cold, strongly interacting matter within an extended version of the Nambu-Jona-Lasinio model that includes flavor-mixing effects and vector interactions. Different values of the relevant model parameters in acceptable ranges are considered. Charge neutrality and beta equilibrium effects, which are especially relevant to the study of compact stars, are also taken into account. In this case, the behavior of leptons is discussed.

We study the $B$ meson semi-inclusive decays into spin-triplet $D$-wave chamonium states ${\psi }_J(J=1,2,3)$ based on the nonrelativistic QCD factorization formula at next-to-leading order in ${\alpha }_s$ and leading order in $v$ (the relative velocity of charm quark and antiquark in charmonium). The finite short-distance coefficients for ${{}^{3}D}_J^{[1]}$ channels are obtained for the first time. The long-distance matrix elements are estimated with the help of potential model and QCD evolution equations. The branching ratios $\mathrm{Br}(B\to {\psi }_{1}X)$ and $\mathrm{Br}(B\to {\psi }_{2}X)$ are, respectively, predicted to be about $6\times {10}^{-4}$ and $2\times {10}^{-3}$, with about 50% relative errors mainly coming from the uncertainties of long-distance matrix elements. The branching ratio $\mathrm{Br}(B\to {\psi }_{3}X)$ can be very small due to a possible cancellation between the ${{}^{3}S}_1^{[8]}$ and ${{}^{3}P}_2^{[8]}$ channels. As an optimistic estimate, we may use the ${{}^{3}S}_1^{[8]}$ channel alone to set up the upper limit for $\mathrm{Br}(B\to {\psi }_{3}X$), which is about $4\times {10}^{-4}$ and may be used in searching for the missing state ${\psi }_3$.

Yang-Mills-Higgs theory, being the standard-model Higgs sector for a suitable choice of a gauge and custodial group, offers a rich set of physics. In particular, in some regions of its parameter space it has QCD-like behavior, while in some other regions it is Higgs-like. Therefore, it is possible to study a plethora of phenomena within a single theory. Here, the physics of the standard-model version is studied using lattice gauge theory at a qualitative level. To this end, the low-lying spectrum in several different channels is obtained for more than 160 different sets of bare parameters throughout the phase diagram. The theory shows quite different behaviors in the different regions, from almost Yang-Mills-like to the one of an essentially free gas of massive photons. Especially, not always is the behavior as naively expected.

The AMS-02 collaboration has recently reported the antiproton to proton ratio with improved accuracy. In view of uncertainties of the production and the propagation of the cosmic rays, the observed ratio is still consistent with the secondary astrophysical antiproton to proton ratio. However, it is nonetheless enticing to examine whether the observed spectrum can be explained by a strongly motivated dark matter, the wino dark matter. As we will show, the antiproton flux from the wino annihilation can explain the observed spectrum well for its mass range 2.5–3 TeV. The fit to data becomes particularly well compared to the case without the annihilation for the thermal wino dark matter case with a mass about 3 TeV. The ratio is predicted to decrease quickly at the energy several hundreds of GeV, which will be confirmed or ruled out in the near future when the AMS-02 experiment accumulates enough data at this higher energy region.

We investigate the probe holographic fermions by using an anisotropic charged black brane solution. We derive the equation of motion of probe bulk fermions with one Fermi momentum along the anisotropic and one along the isotropic directions. We then numerically solve the equation and analyze the properties of Green function with these two momentums. We find in this case the shape of Fermi surface is anisotropic. However, for both Fermi momentums perpendicular to the anisotropic direction, the Fermi surface is isotropic. We verify that our system obeys the recently conjectured bound for thermoelectric diffusion constants for the stable branch of the black brane solutions.

We study the relationship between chiral symmetry breaking and baryons in holographic QCD. We construct a soliton with unit baryon charge in the presence of a nonzero mean value of the scalar bifundamental field, which is dual to the chiral condensate. We obtain a relation between the chiral condensate and the mass of the baryon and find in a clear-cut way that at large values of the condensate the holographic soliton is no longer located on the IR wall. Instead it is split into two halves, which are symmetrically located on the left and right flavor branes. On the other hand we find that the local value of the quark condensate is suppressed in the core of the soliton, which is evidence for a partial chiral symmetry restoration inside the baryon.

A method is suggested for interpolating between small-variable and large-variable asymptotic expansions. The method is based on the self-similar approximation theory resulting in self-similar root approximants. The latter are more general than the two-sided Padé approximants and modified Padé approximants, including these as particular cases. Being more general, the self-similar root approximants guarantee an accuracy that is not worse—and is often better—than that of the Padé approximants. The advantage of the root approximants is in their unambiguous definition and in the possibility of their construction, even when Padé approximants cannot be defined. Conditions for the unique definition of the root approximants are formulated. Several examples from high-energy physics illustrate the method.

We describe a theory living on the null conformal boundary $\mathcal{I}$ of four-dimensional Minkowski space, the states of which include the radiative modes of Yang–Mills theory. The action of a Kac–Moody symmetry algebra on the correlators of these states leads to a Ward identity for asymptotic “large” gauge transformations which is equivalent to the soft gluon theorem. The subleading soft gluon behavior is also obtained from a Ward identity for charges acting as vector fields on the sphere of null generators of $\mathcal{I}$. Correlation functions of the Yang–Mills states are shown to produce the full classical S-matrix of Yang–Mills theory. The model contains additional states arising from nonunitary gravitational degrees of freedom, indicating a relationship with the twistor string of Berkovits and Witten.