We consider the $f(R,T)$ modified theory of gravity, in which the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor of the matter, in order to investigate the dark-matter effects on the galaxy scale. We obtain the metric components for a spherically symmetric and static spacetime in the vicinity of general relativity solutions. However, we concentrate on a specific model of the theory where the matter is minimally coupled to the geometry, and derive the metric components in the galactic halo. Then, we fix the components by the rotational velocities of the galaxies for the model, and show that the mass corresponding to the interaction term (which appears in the Einstein modified field equation) leads to a flat rotation curve in the halo of galaxies. In addition, for the proposed model, the light-deflection angle has been derived and drawn using some observed data.

We suggest that holography can be formulated in terms of the information capacity of the Stückelberg degrees of freedom that maintain gauge invariance of the theory in the presence of an information boundary. These Stückelbergs act as qubits that account for a certain fraction of quantum information. Their information capacity is measured by the ratio of the inverse Stückelberg energy gap to the size of the system. Systems with the smallest gap are maximally holographic. For massless gauge systems this information measure is universally equal to the inverse coupling evaluated at the systems’ length scale. In this language it becomes very transparent why the Stückelberg information capacity of black holes saturates the Bekenstein bound and accounts for the entire information of the system. The physical reason is that the strength of quantum interaction is bounded from below by the gravitational coupling, which scales as area. Observing the striking similarity between the scalings of the energy gap of the boundary Stückelberg modes and the Bogoliubov modes of critical many-body systems, we establish a connection between holography and quantum criticality through the correspondence between these modes.

A supramassive, strongly magnetized millisecond neutron star (NS) has been proposed to be the candidate central engine of at least some short gamma-ray bursts (SGRBs), based on the “internal plateau” commonly observed in the early x-ray afterglow. While a previous analysis shows a qualitative consistency between this suggestion and the Swift SGRB data, the distribution of observed break time $t_b$ is much narrower than the distribution of the collapse time of supramassive NSs for the several NS equations-of-state (EoSs) investigated. In this paper, we study four recently constructed “unified” NS EoSs (BCPM, BSk20, BSk21, and Shen) as well as three developed strange quark star (QS) EoSs within the new confinement density-dependent mass (CDDM) model, labelled as CIDDM, CDDM1, and CDDM2. All the EoSs chosen here satisfy the recent observational constraints of the two massive pulsars of which the masses are precisely measured. We construct sequences of rigidly rotating NS/QS configurations with increasing spinning frequency $f$, from nonrotating ($f=0$) to the Keplerian frequency ($f=f_{\mathrm{K}}$), and provide convenient analytical parametrizations of the results. Assuming that the cosmological NS-NS merger systems have the same mass distribution as the Galactic NS-NS systems, we demonstrate that all except the BCPM NS EoS can reproduce the current 22% supramassive NS/QS fraction constraint as derived from the SGRB data. We simultaneously simulate the observed quantities (the break time $t_b$, the break time luminosity $L_b$, and the total energy in the electromagnetic channel $E_{\text{total}}$) of SGRBs and find that, while equally well reproducing other observational constraints, QS EoSs predict a much narrower $t_b$ distribution than that of the NS EoSs, better matching the data. We therefore suggest that the postmerger product of NS-NS mergers might be fast-rotating supramassive QSs rather than NSs.

Neutrino-pair production and annihilation through nucleon-nucleon bremsstrahlung is included in current supernova simulations by rates that are based on the one-pion-exchange approximation. Here we explore the consequences of bremsstrahlung rates based on modern nuclear interactions for proto-neutron star cooling and the corresponding neutrino emission. We find that despite a reduction of the bremsstrahlung emission by a factor of 2–5 in the neutrinospheric region, models with the improved treatment exhibit only $\lesssim 5\%$ changes of the neutrino luminosities and an increase of $\lesssim 0.7\mathrm{MeV}$ of the average energies of the radiated neutrino spectra, with the largest effects for the antineutrinos of all flavors and at late times. Overall, the proto-neutron star cooling evolution is slowed down modestly by $\lesssim 0.5–1\mathrm{s}$.

We report the results of a directed search for continuous gravitational-wave emission in a broad frequency range (between 50 and 1000 Hz) from the central compact object of the supernova remnant Cassiopeia A (Cas A). The data come from the sixth science run of LIGO, and the search is performed on the volunteer distributed computing network Einstein@Home. We find no significant signal candidate and set the most constraining upper limits to date on the gravitational-wave emission from Cas A, which beat the indirect age-based upper limit across the entire search range. At 170 Hz (the most sensitive frequency range), we set 90% confidence upper limits on the gravitational-wave amplitude $h_0$ of $\sim 2.9\times {10}^{-25}$, roughly twice as constraining as the upper limits from previous searches on Cas A. The upper limits can also be expressed as constraints on the ellipticity of Cas A; with a few reasonable assumptions, we show that at gravitational-wave frequencies greater than 300 Hz we can exclude an ellipticity of $\gtrsim {10}^{-5}$.

Motivated by the continuous experimental investigations of $X(1835)$ in three-body decay channels like ${\eta }^{\prime }{\pi }^{+}{\pi }^{-}$, we investigate the ${\eta }^{\prime }K\overline{K}$ system with the aim of searching for bound states and/or resonances when the dynamics involved in the $K\overline{K}$ subsystem can form the resonances: $f_0(980)$ in isospin zero or $a_0(980)$ in isospin 1. For this, we solve the Faddeev equations for the three-body system. The input two-body $t$ matrices are obtained by solving Bethe-Salpeter equations in a coupled channel formalism. As a result, no signal of a three-body bound state or resonance is found.

We study a model with a Higgs-like dilaton and a standard model gauge-singlet scalar dark matter candidate. We begin by updating the status of identifying the observed 125 GeV Higgs-like boson with the pseudo Nambu-Goldstone boson that arises from the spontaneous breaking of scale invariance using recent Higgs boson signal strength measurements by the ATLAS and CMS collaborations. We then constrain the extended model with recent constraints on the Higgs invisible width, the observed dark matter relic abundance and the latest dark matter direct detection limits. We found that the magnitude of the dilaton-$\gamma \gamma$ and dilaton-glue-glue coupling is constrained to be close to the standard model values. The mass of the dark matter candidate is constrained to be greater than half the dilaton mass by relic abundance limits and Higgs invisible width limits. Dark matter direct detection limits allow only small mass regions which will be further constrained by upcoming Dark Matter Experiment using Argon Pulse-shape measurements.

We investigate the in-medium behavior of mesons at finite temperature and baryon chemical potential within a soft-wall model of AdS/QCD. We use a quartic scalar potential to obtain the correct form of chiral symmetry breaking. At zero quark mass, the chiral phase transition is second order, becoming a crossover at physical quark mass. At zero baryon chemical potential, we find a chiral transition temperature of 155 MeV in the chiral limit and a pseudotransition temperature of 151 MeV at physical quark mass, consistent with lattice results. In the low-temperature limit, the second-order transition occurs at a baryon chemical potential of 566 MeV while the rapid crossover occurs at 559 MeV. A new parametrization of the dilaton profile results in improved meson spectra. Meson melting occurs at a lower temperature and chemical potential than the chiral phase transition, so the vector-axial vector mass splitting remains constant until the bound states melt.

We study the extended colored Zee-Babu model introducing a vectorlike quark and singlet scalar. The active neutrino mass matrix and muon anomalous magnetic moment, which can be fitted to experimental data satisfying the constraints from the flavor-changing neutral current, are analyzed. Then, we discuss the constraint from $h_{\mathrm{SM}}\to \gamma \gamma$, the implication of an exotic diphoton resonance as a signature of the model, and the stability of the scalar potential. In addition, we discuss the signature of our model via vectorlike quark production.

In the minimal seesaw model, we derive required constraints on Dirac neutrino masses inducing maximal $CP$ violation in neutrino oscillations. If the maximal atmospheric neutrino mixing is further assumed, Dirac neutrino masses are uniquely determined to respect $\mu \text{−}\tau$ flavored $CP$ symmetry for neutrinos.

We investigate $B_s{\pi }^{+}$ scattering in $s$-wave using lattice QCD in order to search for an exotic resonance $X(5568)$ with flavor $\overline{b}s\overline{d}u$; such a state was recently reported by D0 but was not seen by LHCb. If $X(5568)$ with $J^P=0^{+}$ exists, it can strongly decay only to $B_s{\pi }^{+}$ and lies significantly below all other thresholds, which makes a lattice search for $X(5568)$ cleaner and simpler than for other exotic candidates. Both an elastic resonance in $B_s{\pi }^{+}$ as well as a deeply bound $B^{+}{\overline{K}}^0$ would lead to distinct signatures in the energies of lattice eigenstates, which are not seen in our simulation. We therefore do not find a candidate for $X(5568)$ with $J^P=0^{+}$ in agreement with the recent LHCb result. The extracted $B_s{\pi }^{+}$ scattering length is compatible with zero within the error.

Spectra of the neutral heavy mesons, ${\eta }_c(1S,2S)$, $J/\psi$, $\psi (2S)$, ${\eta }_b(1S,2S,3S)$, $\mathrm{\Upsilon }(1S,2S,3S)$, $D$, $D^{*}$, $B$, $B^{*}$, $B_s$ and $B_s^{*}$, in a homogeneous magnetic field are analyzed by using a potential model with constituent quarks. To obtain anisotropic wave functions and the corresponding eigenvalues, the cylindrical Gaussian expansion method is applied, where the wave functions for transverse and longitudinal directions in the cylindrical coordinate are expanded by the Gaussian bases separately. Energy level structures in the wide range of magnetic fields are obtained and the deformation of the wave functions is shown, which reflects effects of the spin mixing, the Zeeman splitting and quark Landau levels. The contribution from the magnetic catalysis in heavy-light mesons is discussed as a change of the light constituent quark mass.

The exclusive processes are considered, where a pointlike source of heavy quark-antiquark pairs $Q\overline{Q}$, e.g., their electromagnetic current, produces a pair consisting of a heavy quarkoniumlike exotic meson (tetraquark) or baryon (pentaquark) and a light meson or an antibaryon. For a sufficiently large mass of the heavy quark $m_Q$ there is a range of the energy $E$ above the $Q\overline{Q}$ threshold, where $E\ll m_Q$ and still the energy is large compared to the strong interaction scale, $E\gg {\mathrm{\Lambda }}_{\mathrm{QCD}}$. It is shown that in this energy range, where the heavy quarks are nonrelelativistic, a specific “intermediate asymptotic” behavior sets in determined by the number $n$ of the pairs of constituent quarks, with the rate scaling as $E^{1-n}$.

We discuss a test of the Standard Model fermion mass origin in models of dynamical electroweak symmetry breaking. The couplings of composite pseudoscalar resonances to top quarks allow us to distinguish high-scale extended-technicolor-type fermion mass generation from fermion partial compositeness and low-scale mass generation via an induced vacuum expectation value of a doublet coupled to the composite sector. These different possible origins of fermion masses are thus accessible via weak-scale physics searched for at the LHC.

A class of Polyakov-loop-modified Nambu–Jona-Lasinio models has been used to support a conjecture that numerical simulations of lattice-regularized QCD defined with a chiral chemical potential can provide information about the existence and location of a critical end point in the QCD phase diagram drawn in the plane spanned by baryon chemical potential and temperature. That conjecture is challenged by conflicts between the model results and analyses of the same problem using simulations of lattice-regularized QCD (lQCD) and well-constrained Dyson-Schwinger equation (DSE) studies. We find the conflict is resolved in favor of the lQCD and DSE predictions when both a physically motivated regularization is employed to suppress the contribution of high-momentum quark modes in the definition of the effective potential connected with the Polyakov-loop-modified Nambu–Jona-Lasinio models and the four-fermion coupling in those models does not react strongly to changes in the mean field that is assumed to mock-up Polyakov-loop dynamics. With the lQCD and DSE predictions thus confirmed, it seems unlikely that simulations of lQCD with ${\mu }_5>0$ can shed any light on a critical end point in the regular QCD phase diagram.

We show that the masses of the lowest-lying heavy baryons can be very well described in a pion mean-field approach. We consider a heavy baryon as a system consisting of the $N_c-1$ light quarks that induce the pion mean field and a heavy quark as a static color source under the influence of this mean field. In this approach we derive a number of model-independent relations and calculate the heavy-baryon masses using those of the lowest-lying light baryons as input. The results are in remarkable agreement with the experimental data. In addition, the mass of the ${\mathrm{\Omega }}_b^{*}$ baryon is predicted.

According to the gauge/gravity duality conjecture, the thermodynamics of gauge theory describing D-branes corresponds to that of black branes in superstring theory. We test this conjecture directly in the case of D0-branes by applying Monte Carlo methods to the corresponding gauge theory, which takes the form of the Banks-Fischler-Shenker-Susskind (BFSS) matrix quantum mechanics. In particular, we take the continuum limit by extrapolating the UV cutoff to infinity. First we perform simulations at large $N$ so that string loop corrections can be neglected on the gravity side. Our results for the internal energy exhibit the temperature dependence consistent with the prediction including the ${\alpha }^{\prime }$ corrections. Next we perform simulations at small $N$ but at lower temperature so that the ${\alpha }^{\prime }$ corrections can be neglected on the gravity side. Our results are consistent with the prediction including the leading string loop correction, which suggests that the conjecture holds even at finite $N$.

I analyze the quantum mechanical scattering off a topological defect (such as a Dirac monopole) as well as a Yukawa-like potential(s) representing the typical effects of strong interactions. This system, due to the presence of a short-range potential, can be analyzed using the powerful technique of the complex angular momenta which, so far, has not been employed in the presence of monopoles (nor of other topological solitons). Due to the fact that spatial spherical symmetry is achieved only up to internal rotations, the partial wave expansion becomes very similar to the Jacob-Wick helicity amplitudes for particles with spin. However, since the angular-momentum operator has an extra “internal” contribution, fixed cuts in the complex angular momentum plane appear. Correspondingly, the background integral in the Regge formula does not decrease for large values of $|\cos \theta |$ (namely, large values of the Mandelstam variable $s$). Hence, the experimental observation of this kind of behavior could be a direct signal of nontrivial topological structures in strong interactions. The possible relations of these results with the soft Pomeron are shortly analyzed.

The Wegner $Z_2$ gauge theory-$Z_2$ Ising spin model duality in ($2+1$) dimensions is revisited and derived through a series of canonical transformations. The Kramers-Wannier duality is similarly obtained. The Wegner $Z_2$ gauge-spin duality is directly generalized to SU(N) lattice gauge theory in ($2+1$) dimensions to obtain the SU(N) spin model in terms of the SU(N) magnetic fields and their conjugate SU(N) electric scalar potentials. The exact and complete solutions of the $Z_2$, U(1), SU(N) Gauss law constraints in terms of the corresponding spin or dual potential operators are given. The gauge-spin duality naturally leads to a new gauge invariant magnetic disorder operator for SU(N) lattice gauge theory which produces a magnetic vortex on the plaquette. A variational ground state of the SU(2) spin model with nearest neighbor interactions is constructed to analyze SU(2) gauge theory.

We explicitly show perturbative gauge fixing independence of the tunneling rate to a stable radiatively induced vacuum in the Abelian Higgs model. We work with a class of $R_{\xi }$ gauges in the presence of both dimensionless and dimensionful gauge fixing parameters. We show that Nielsen identities survive the inclusion of higher order operators and compute the tunnelling rate to the vacua modified by the nonrenormalizable operators in a gauge invariant manner. We also discuss implications of this method for the complete Standard Model.