The ideal magnetohydrodynamic theorem on the conservation of the magnetic connections between plasma elements is generalized to relativistic plasmas in curved spacetime. The connections between plasma elements, which are established by a covariant connection equation, display a particularly complex structure in curved spacetime. Nevertheless, it is shown that these connections can be interpreted in terms of magnetic field lines alone by adopting a $3+1$ foliation of spacetime.

Binary black hole (BBH) mergers provide a prime source for current and future interferometric gravitational wave observatories. Massive BBH mergers may often take place in plasma-rich environments, leading to the exciting possibility of a concurrent electromagnetic (EM) signal observable by traditional astronomical facilities. However, many critical questions about the generation of such counterparts remain unanswered. We explore mechanisms that may drive EM counterparts with magnetohydrodynamic simulations treating a range of scenarios involving equal-mass black-hole binaries immersed in an initially homogeneous fluid with uniform, orbitally aligned magnetic fields. We find that the time development of Poynting luminosity, which may drive jetlike emissions, is relatively insensitive to aspects of the initial configuration. In particular, over a significant range of initial values, the central magnetic field strength is effectively regulated by the gas flow to yield a Poynting luminosity of $10^{45}-{10}^{46}{\rho }_{\text{−}13}{M_8}^2\mathrm{erg}{\mathrm{s}}^{-1}$, with BBH mass scaled to $M_8\equiv M/({10}^8{M}_{\odot })$ and ambient density ${\rho }_{\text{−}13}\equiv \rho /({10}^{-13}\mathrm{g}{\mathrm{cm}}^{-3})$. We also calculate the direct plasma synchrotron emissions processed through geodesic ray-tracing. Despite lensing effects and dynamics, we find the observed synchrotron flux varies little leading up to merger.

We study M1-transitions involving mesons: $B_c(1s)$, $B_c^{*}(1s)$, $B_c(2s)$, $B_c^{*}(2s)$, $B_c(3s)$, and $B_c^{*}(3s)$ in the relativistic independent quark (RIQ) model based on a flavor independent average potential in the scalar-vector harmonic form. The transition form factor for $B_c^{*}\to B_c\gamma$ is found to have analytical continuation from spacelike to physical timelike region. Our predicted coupling constant $g_{B_c^{*}{B}_c}=0.34{\mathrm{GeV}}^{-1}$ and decay width $\mathrm{\Gamma }(B_c^{*}\to B_c\gamma )=23\mathrm{eV}$ agree with other model predictions. In view of possible observation of $B_c$ and $B_c^{*}$ s-wave states at LHC and Z-factory and potential use of theoretical estimate on M1-transitions, we investigate the allowed as well as hindered transitions of orbitally excited $B_c$-meson states and predict their decay widths in overall agreement with other model predictions. We consider the typical case of $B_c^{*}(1s)\to B_c(1s)\gamma$, where our predicted decay width which is found quite sensitive to the mass difference between $B_c^{*}$ and $B_c$ mesons may help in determining the mass of $B_c^{*}$ experimentally.

A recently developed variational resummation technique, incorporating renormalization group properties consistently, has been shown to solve the scale dependence problem that plagues the evaluation of thermodynamical quantities, e.g., within the framework of approximations such as in the hard-thermal-loop resummed perturbation theory. This method is used in the present work to evaluate thermodynamical quantities within the two-dimensional nonlinear sigma model, which, apart from providing a technically simpler testing ground, shares some common features with Yang-Mills theories, like asymptotic freedom, trace anomaly and the nonperturbative generation of a mass gap. The present application confirms that nonperturbative results can be readily generated solely by considering the lowest-order (quasiparticle) contribution to the thermodynamic effective potential, when this quantity is required to be renormalization group invariant. We also show that when the next-to-leading correction from the method is accounted for, the results indicate convergence, apart from optimally preserving, within the approximations here considered, the sought-after scale invariance.

We calculate at the leading order in ${\alpha }_s$ the QCD amplitude for exclusive neutrino production of a $D^{*}$ or $D_s^{*}$ charmed vector meson on a nucleon. We work in the framework of the collinear QCD approach where generalized parton distributions (GPDs) factorize from perturbatively calculable coefficient functions. We include $O(m_c)$ terms in the coefficient functions and the $O(m_D)$ term in the definition of heavy meson distribution amplitudes. The show that the analysis of the angular distribution of the decay $D_{(s)}^{*}\to D_{(s)}\pi$ allows us to access the transversity gluon GPDs.

We investigate the interplay between the (light-light quark) chiral condensate and heavy-light quark condensate induced by the QCD Kondo effect, which is described by an effective Lagrangian with four-point interactions and the mean-field approximation. We find that the appearance of Kondo condensates decreases the critical chemical potential of the chiral condensate. In the region near the critical chemical potential, a coexistence phase with two kinds of condensates can appear. The behavior of such an interplay at finite temperature and with nonzero current light-quark mass is also discussed.

The accuracy of the Gounaris-Sakurai pion electromagnetic form factor model at the elastic region, in which just the ${\rho }^0(770)$ resonance appears, is investigated by the particular analysis of the most accurate P-wave isovector $\pi \pi$ scattering phase shift ${\delta }_1^1(t)$ data, obtained by the Garcia-Martin-Kamiński-Peláez-Yndurain approach, and by an application of the Unitary&Analytic pion electromagnetic structure model to a description of the newest precise data on the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ process.

We introduce parametrizations of hadronic three-body $B$ and $D$ weak decay amplitudes that can be readily implemented in experimental analyses and are a sound alternative to the simplistic and widely used sum of Breit-Wigner type amplitudes, also known as the isobar model. These parametrizations can be particularly useful in the interpretation of $CP$ asymmetries in the Dalitz plots. They are derived from previous calculations based on a quasi-two-body factorization approach in which two-body hadronic final-state interactions are fully taken into account in terms of unitary $S$- and $P$-wave $\pi \pi$, $\pi K$, and $K\overline{K}$ form factors. These form factors can be determined rigorously, fulfilling fundamental properties of quantum field-theory amplitudes such as analyticity and unitarity, and are in agreement with the low-energy behavior predicted by effective theories of QCD. They are derived from sets of coupled-channel equations using $T$-matrix elements constrained by experimental meson-meson phase shifts and inelasticities, chiral symmetry, and asymptotic QCD. We provide explicit amplitude expressions for the decays $B^{\pm }\to {\pi }^{+}{\pi }^{-}{\pi }^{\pm }$, $B\to K{\pi }^{+}{\pi }^{-}$, $B^{\pm }\to K^{+}{K}^{-}{K}^{\pm }$, $D^{+}\to {\pi }^{-}{\pi }^{+}{\pi }^{+}$, $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$, and $D^0\to K_S^0{\pi }^{+}{\pi }^{-}$, for which we have shown in previous studies that this approach is phenomenologically successful; in addition, we provide expressions for the $D^0\to K_S^0{K}^{+}{K}^{-}$ decay. Other three-body hadronic channels can be parametrized likewise.

We study universality of geometric gauge sectors in the string landscape in the context of F-theory compactifications. A finite time construction algorithm is presented for $\frac{4}{3}\times 2.96\times {10}^{755}$ F-theory geometries that are connected by a network of topological transitions in a connected moduli space. High probability geometric assumptions uncover universal structures in the ensemble without explicitly constructing it. For example, non-Higgsable clusters of seven-branes with intricate gauge sectors occur with a probability above $1–1.01\times {10}^{-755}$, and the geometric gauge group rank is above 160 with probability 0.999995. In the latter case there are at least 10 $E_8$ factors, the structure of which fixes the gauge groups on certain nearby seven-branes. Visible sectors may arise from $E_6$ or $SU(3)$ seven-branes, which occur in certain random samples with probability $\simeq 1/200$.

The Atiyah-Patodi-Singer (APS) index theorem attracts attention for understanding physics on the surface of materials in topological phases. The mathematical setup for this theorem is, however, not directly related to the physical fermion system, as it imposes on the fermion fields a nonlocal boundary condition known as the “APS boundary condition” by hand, which is unlikely to be realized in the materials. In this work, we attempt to reformulate the APS index in a “physicist-friendly” way for a simple setup with $U(1)$ or $SU(N)$ gauge group on a flat four-dimensional Euclidean space. We find that the same index as APS is obtained from the domain-wall fermion Dirac operator with a local boundary condition, which is naturally given by the kink structure in the mass term. As the boundary condition does not depend on the gauge fields, our new definition of the index is easy to compute with the standard Fujikawa method.

We consider the transport of conserved charges in spatially inhomogeneous quantum systems with a discrete lattice symmetry. We analyze the retarded two-point functions involving the charges and the associated currents at long wavelengths, compared to the scale of the lattice, and, when the dc conductivities are finite, extract the hydrodynamic modes associated with diffusion of the charges. We show that the dispersion relations of these modes are related to the eigenvalues of a specific matrix constructed from the dc conductivities and certain thermodynamic susceptibilities, thus obtaining generalized Einstein relations. We illustrate these general results in the specific context of relativistic hydrodynamics where translation invariance is broken using spatially inhomogeneous and periodic deformations of the stress tensor and the conserved $U(1)$ currents. Equivalently, this corresponds to considering hydrodynamics on a curved manifold, with a spatially periodic metric and chemical potential, and we obtain the dispersion relations for the heat and charge diffusive modes.

An important hurdle to be faced by any model proposing a resolution to the cosmological constant problem is Weinberg’s venerable no go theorem. This theorem states that no local field equations including classical gravity can have a flat Minkowski solution for generic values of the parameters; in other words, the no go theorem forbids the existence of any solution to the cosmological constant problem within local field theories without fine tuning. Though the original Weinberg theorem is valid only in classical gravity, in this article we prove that this theorem holds even in quantum gravity. Our proof is very general since it makes use of the Becchi-Rouet-Stora-Tyutin (BRST) invariance emerging after the gauge fixing of general coordinate invariance and does not depend on the detail of quantum gravity.

We establish an analogy between superconductor-metal interfaces and the quantum physics of a black hole, using the proximity effect. We show that the metal-superconductor interface can be thought of as an event horizon and Andreev reflection from the interface is analogous to the Hawking radiation in black holes. We describe quantum information transfer in Andreev reflection with a final state projection model similar to the Horowitz-Maldacena model for black hole evaporation. We also propose the Andreev reflection analogue of Hayden and Preskill’s description of a black hole final state, where the black hole is described as an information mirror. The analogy between crossed Andreev reflections and Einstein-Rosen bridges is discussed: our proposal gives a precise mechanism for the apparent loss of quantum information in a black hole by the process of nonlocal Andreev reflection, transferring the quantum information through a wormhole and into another universe. Given these established connections, we conjecture that the final quantum state of a black hole is exactly the same as the ground state wave function of the superconductor/superfluid in the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity; in particular, the infalling matter and the infalling Hawking quanta, described in the Horowitz-Maldacena model, forms a Cooper pairlike singlet state inside the black hole. A black hole evaporating and shrinking in size can be thought of as the analogue of Andreev reflection by a hole where the superconductor loses a Cooper pair. Our model does not suffer from the black hole information problem since Andreev reflection is unitary. We also relate the thermodynamic properties of a black hole to that of a superconductor, and propose an experiment which can demonstrate the negative specific heat feature of black holes in a growing/evaporating condensate.

We present an analytical waveform family describing gravitational waves (GWs) from the inspiral, merger, and ringdown of nonspinning black-hole binaries including the effect of several nonquadrupole modes [$(\ell =2,m=\pm 1),(\ell =3,m=\pm 3),(\ell =4,m=\pm 4)$ apart from $(\ell =2,m=\pm 2)$]. We first construct spin-weighted spherical harmonics modes of hybrid waveforms by matching numerical-relativity simulations (with mass ratio 1–10) describing the late inspiral, merger, and ringdown of the binary with post-Newtonian/effective-one-body waveforms describing the early inspiral. An analytical waveform family is constructed in frequency domain by modeling the Fourier transform of the hybrid waveforms making use of analytical functions inspired by perturbative calculations. The resulting highly accurate, ready-to-use waveforms are highly faithful (unfaithfulness $\simeq {10}^{-4}–{10}^{-2}$) for observation of GWs from nonspinning black-hole binaries and are extremely inexpensive to generate.

The evolution of electromagnetic and thermodynamic fields in a nonideal fluid is studied in the framework of ultrarelativistic transverse magnetohydrodynamics (MHD), which is essentially characterized by electric and magnetic fields being transverse to the fluid velocity and translational invariance in the transverse plane. Extending the method of self-similar solutions of relativistic hydrodynamics to the case of nonconserved charges, the differential equations of nonideal transverse MHD are solved, and two novel sets of self-similar solutions are derived. The first set turns out to be a boost-invariant and exact solution, which is characterized by nonrotating electric and magnetic fields. The second set is a nonboost-invariant solution, which is characterized by rotating electric and magnetic fields. The rotation occurs with increasing rapidity $\eta$, as the angular velocity is defined by ${\omega }_0\equiv \frac{\partial \zeta }{\partial \eta }=\frac{\partial \varphi }{\partial \eta }$, with $\zeta$ and $\varphi$ being the angles of local electric and magnetic vectors with respect to a certain fixed axis in the transverse plane. For both sets of solutions, the electric and magnetic fields are either parallel or antiparallel to each other in the local rest frame of the fluid. Performing a complete numerical analysis, the effects of finite electric conductivity as well as electric and magnetic susceptibilities of the medium on the evolution of rotating and nonrotating MHD solutions are explored, and the interplay between the angular velocity ${\omega }_0$ and these quantities is scrutinized. The lifetime of electromagnetic fields and the evolution of the temperature of the electromagnetized fluid are shown to be affected by ${\omega }_0$.

In the presence of nonstandard neutrino interactions (NSI), oscillation data are affected by a degeneracy which allows the solar mixing angle to be in the second octant (also known as the dark side) and implies a sign flip of the atmospheric mass-squared difference. This leads to an ambiguity in the determination of the ordering of neutrino masses, one of the main goals of the current and future experimental neutrino program. We show that the recent observation of coherent neutrino-nucleus scattering by the COHERENT experiment, in combination with global oscillation data, excludes the NSI degeneracy at the $3.1\sigma$ ($3.6\sigma$) C.L. for NSI with up (down) quarks.

We consider a linear sigma model describing $2N_f^2$ bosons ($\sigma$, ${\mathbf{a}}_{\mathbf{0}}$, ${\eta }^{\prime }$ and $\mathbf{\pi }$) as an approximate effective theory for a $SU(3)$ local gauge theory with $N_f$ Dirac fermions in the fundamental representation. The model has a renormalizable $U(N_f{)}_L\otimes U(N_f{)}_R$ invariant part, which has an approximate $O(2N_f^2)$ symmetry, and two additional terms, one describing the effects of a $SU(N_f{)}_V$ invariant mass term and the other the effects of the axial anomaly. We calculate the spectrum for arbitrary $N_f$. Using preliminary and published lattice results from the LatKMI collaboration, we found combinations of the masses that vary slowly with the explicit chiral symmetry breaking and $N_f$. This suggests that the anomaly term plays a leading role in the mass spectrum and that simple formulas such as $M_{\sigma }^2\simeq (2/N_f-C_{\sigma })M_{{\eta }^{\prime }}^2$ should apply in the chiral limit. Lattice measurements of $M_{{\eta }^{\prime }}^2$ and of approximate constants such as $C_{\sigma }$ could help in locating the boundary of the conformal window. We show that our calculation can be adapted for arbitrary representations of the gauge group and in particular to the minimal model with two sextets, where similar patterns are likely to apply.

We calculate the branching ratios and polarization fractions of the $B\to a_1{b}_1$ decays in the perturbative QCD(pQCD) approach at leading order, where $a_1(b_1)$ stands for the axial-vector $a_1(1260)[b_1(1235)]$ state. By combining the phenomenological analyses with the perturbative calculations, we find the following results: (a) the large decay rates around ${10}^{-5}$ to ${10}^{-6}$ of the $B\to a_1{b}_1$ decays dominated by the longitudinal polarization(except for the $B^{+}\to b_1^{+}{a}_1^0$ mode) are predicted and basically consistent with those in the QCD factorization(QCDF) within errors, which are expected to be tested by the Large Hadron Collider and Belle-II experiments. The large $B^0\to a_1^0{b}_1^0$ branching ratio could provide hints to help explore the mechanism of the color-suppressed decays. (b) the rather different QCD behaviors between the $a_1$ and $b_1$ mesons result in the destructive(constructive) contributions in the nonfactorizable spectator diagrams with $a_1(b_1)$ emission. Therefore, an interesting pattern of the branching ratios appears for the color-suppressed $B^0\to a_1^0{a}_1^0,a_1^0{b}_1^0$, and $b_1^0{b}_1^0$ modes in the pQCD approach, $\mathrm{BR}(B^0\to b_1^0{b}_1^0)>\mathrm{BR}(B^0\to a_1^0{b}_1^0)\gtrsim \mathrm{BR}(B^0\to a_1^0{a}_1^0)$, which is different from $\mathrm{BR}(B^0\to b_1^0{b}_1^0)\sim \mathrm{BR}(B^0\to a_1^0{b}_1^0)\gtrsim \mathrm{BR}(B^0\to a_1^0{a}_1^0)$ in the QCDF and would be verified at future experiments. (c) the large naive factorization breaking effects are observed in these $B\to a_1{b}_1$ decays. Specifically, the large nonfactorizable spectator(weak annihilation) amplitudes contribute to the $B^0\to b_1^{+}{a}_1^{-}(B^{+}\to a_1^{+}{b}_1^0\text{and}{B}^{+}\to b_1^{+}{a}_1^0)$ mode(s), which demand confirmations via the precise measurements. Furthermore, the different phenomenologies shown among $B\to a_1{b}_1$, $B\to a_1{a}_1$, and $B\to b_1{b}_1$ decays are also expected to be tested stringently, which could shed light on the typical QCD dynamics involved in these modes, even further distinguish those two popular pQCD and QCDF approaches.

We present a new veto procedure to distinguish between continuous gravitational wave (CW) signals and the detector artifacts that can mimic their behavior. The veto procedure exploits the fact that a long-lasting coherent disturbance is less likely than a real signal to exhibit a Doppler modulation of astrophysical origin. Therefore, in the presence of an outlier from a search, we perform a multistep search around the frequency of the outlier with the Doppler modulation turned off (DM-off), and compare these results with the results from the original (DM-on) search. If the results from the DM-off search are more significant than those from the DM-on search, the outlier is most likely due to an artifact rather than a signal. We tune the veto procedure so that it has a very low false dismissal rate. With this veto, we are able to identify as coherent disturbances $>99.9\%$ of the 6349 candidates from the recent all-sky low-frequency Einstein@Home search on the data from the Advanced LIGO O1 observing run [LIGO and Virgo Collaborations, Phys. Rev. D 96, 122004 (2017)]. We present the details of each identified disturbance in the Appendix.