We consider a modified Randall-Sundrum (RS) framework between the Planck scale and the grand unified theory (GUT) scale. In this scenario, RS works as a theory of flavor and not as a solution to the hierarchy problem. The latter is resolved by supersymmetrizing the bulk, so that the minimal supersymmetric standard model is the effective four-dimensional theory. Matter fields are localized in the bulk in order to fit fermion-mass and mixing data. If $R$-parity violating (${\cancel{R}}_p$) terms are allowed in the superpotential, their orders of magnitude throughout flavor space are then predicted, resulting in rich flavor textures. If the ${\cancel{R}}_p$ contributions to neutrino masses are somewhat suppressed, then lepton-number violating models exist which explain the neutrino oscillation data while not being in contradiction with current experimental bounds. Another promising model is one where baryon number is violated and Dirac neutrino masses result solely from fermion localization. We sketch the likely discovery signatures of the baryon-number and the lepton-number violating cases.

We revisit a class of $Z^{\prime }$ explanations of the anomalies found by the LHCb collaboration in $B$ decays, and show that the scenario is tightly constrained by a combination of constraints: (i) LHC searches for dimuon resonances, (ii) perturbativity of the $Z^{\prime }$ couplings; (iii) the $B_s$ mass difference, and (iv) electroweak precision data. Solutions are found by suppressing the $Z^{\prime }$ coupling to electrons and to light quarks and/or by allowing for a $Z^{\prime }$ decay width into dark matter. We also present a simplified framework where a TeV-scale $Z^{\prime }$ gauge boson that couples to standard leptons as well as to new heavy vectorlike leptons, can simultaneously accommodate the LHCb anomalies and the muon $g-2$ anomaly.

In a previous paper [N. Haque et al., J. High Energy Phys. 05 (2014) 27], we calculated the three-loop thermodynamic potential of QCD at finite temperature $T$ and quark chemical potentials ${\mu }_q$ using the hard-thermal-loop perturbation theory (HTLpt) reorganization of finite temperature and density QCD. The result allows us to study the thermodynamics of QCD at finite temperature and finite baryon, strangeness, and isospin chemical potentials ${\mu }_B$, ${\mu }_S$, and ${\mu }_I$. We calculate the pressure at nonzero ${\mu }_B$ and ${\mu }_I$ with ${\mu }_S=0$, and the energy density, the entropy density, the trace anomaly, and the speed of sound at nonzero ${\mu }_I$ with ${\mu }_B={\mu }_S=0$. The second- and fourth-order isospin susceptibilities are calculated at ${\mu }_B={\mu }_S={\mu }_I=0$. Our results can be directly compared to lattice QCD without Taylor expansions around ${\mu }_q=0$ since QCD has no sign problem at ${\mu }_B={\mu }_S=0$ and finite isospin chemical potential ${\mu }_I$.

In this paper we consider $CP$-violating new-physics contributions to the decay $t\to b\overline{b}c$. We examine the prospects for detecting such new physics at the LHC, which requires studying the process $gg\to t(\to b\overline{b}c)\overline{t}(\to \overline{b}\ell \overline{\nu })$. We find two observables that can be used to reveal the presence of $CP$-violating new physics in $t\to b\overline{b}c$. They are (i) the partial-rate asymmetry and (ii) the triple-product correlations involving the momenta of various particles associated with the interaction. A Monte Carlo analysis is performed to determine how well these observables can be used to detect the presence of new physics, and to measure its parameters. We find that there is little difficulty in extracting the value of the relevant new-physics parameter from the partial-rate asymmetry. For the triple-product correlations, we test multiple strategies that can be used for the extraction of the corresponding combination of new-physics parameters.

We study jet substructures of a boosted polarized top quark, which undergoes the hadronic decay $t\to bu\overline{d}$, in the perturbative QCD framework, focusing on the energy profile and the differential energy profile. These substructures are factorized into the convolution of a hard top-quark decay kernel with a bottom-quark jet function and a $W$-boson jet function, where the latter is further factorized into the convolution of a hard $W$-boson decay kernel with two light-quark jet functions. Computing the hard kernels to leading order in QCD and including the resummation effect in the jet functions, we show that the differential jet energy profile is a useful observable for differentiating the helicity of a boosted hadronic top quark: a right-handed top jet exhibits quick descent of the differential energy profile with the inner test cone radius $r$, which is attributed to the $\mathrm{V}\text{−}\mathrm{A}$ structure of weak interaction and the dead-cone effect associated with the $W$-boson jet. The above helicity differentiation may help reveal the chiral structure of physics beyond the standard model at high energies.

We investigate the magnetohydrodynamics in the presence of an external magnetic field following the power-law decay in proper time and having spatial inhomogeneity characterized by a Gaussian distribution in one of transverse coordinates under the Bjorken expansion. The leading-order solution is obtained in the weak-field approximation, where both energy density and fluid velocity are modified. It is found that the spatial gradient of the magnetic field results in transverse flow, where the flow direction depends on the decay exponents of the magnetic field. We suggest that such a magnetic-field-induced effect might influence anisotropic flow in heavy ion collisions.

We address the problem of $J/\psi$ spin alignment in hadron-hadron collisions and propose a natural solution to it using an extended nonrelativistic QCD model where the emission of soft gluons is treated as a series of explicit color-electric dipole transitions.

We present results for the QED contributions to the anomalous magnetic moment of the muon containing closed electron loops. The main focus is on perturbative corrections at four-loop order where the external photon couples to the external muon. Furthermore, all four-loop contributions involving simultaneously a closed electron and tau loop are computed. In combination with our recent results on the light-by-light-type corrections (see Ref. [1]), the complete four-loop electron-loop contribution to the anomalous magnetic moment of the muon has been obtained with an independent calculation. Our calculation is based on an asymptotic expansion in the ratio of the electron and the muon mass and shows the importance of higher-order terms in this ratio. We perform a detailed comparison with results available in the literature and find good numerical agreement. As a byproduct, we present analytic results for the on-shell muon mass and wave function renormalization constants at three-loop order including massive closed electron and tau loops, which we also calculated using the method of asymptotic expansion.

We report inclusive and exclusive measurements for ${\chi }_{c1}$ and ${\chi }_{c2}$ production in $B$ decays. We measure $\mathcal{B}(B\to {\chi }_{c1}X)=(3.03\pm 0.05(\mathrm{stat})\pm 0.24(\mathrm{syst}))\times {10}^{-3}$ and $\mathcal{B}(B\to {\chi }_{c2}X)=(0.70\pm 0.06(\mathrm{stat})\pm 0.10(\mathrm{syst}))\times {10}^{-3}$. For the first time, ${\chi }_{c2}$ production in exclusive $B$ decays in the modes $B^0\to {\chi }_{c2}{\pi }^{-}{K}^{+}$ and $B^{+}\to {\chi }_{c2}{\pi }^{+}{\pi }^{-}{K}^{+}$ has been observed, along with first evidence for the $B^{+}\to {\chi }_{c2}{\pi }^{+}{K}_S^0$ decay mode. For ${\chi }_{c1}$ production, we report the first observation in the $B^{+}\to {\chi }_{c1}{\pi }^{+}{\pi }^{-}{K}^{+}$, $B^0\to {\chi }_{c1}{\pi }^{+}{\pi }^{-}{K}_S^0$ and $B^0\to {\chi }_{c1}{\pi }^0{\pi }^{-}{K}^{+}$ decay modes. Using these decay modes, we observe a difference in the production mechanism of ${\chi }_{c2}$ in comparison to ${\chi }_{c1}$ in $B$ decays. In addition, we report searches for $X(3872)$ and ${\chi }_{c1}(2P)$ in the $B^{+}\to ({\chi }_{c1}{\pi }^{+}{\pi }^{-})K^{+}$ decay mode. The reported results use $772\times {10}^6$ $B\overline{B}$ events collected at the $\mathrm{\Upsilon }(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider.

We measure the time-dependent $CP$ asymmetry in the radiative-penguin decay $B^0\to K_S^0{\pi }^{-}{\pi }^{+}\gamma$, using a sample of $471\times {10}^6$ $\mathrm{\Upsilon }(4S)\to B\overline{B}$ events recorded with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ storage ring at SLAC. Using events with $m_{K\pi \pi }<1.8\mathrm{GeV}/c^2$, we measure the branching fractions of $B^{+}\to K^{+}{\pi }^{-}{\pi }^{+}\gamma$ and $B^0\to K^0{\pi }^{-}{\pi }^{+}\gamma$, the branching fractions of the kaonic resonances decaying to $K^{+}{\pi }^{-}{\pi }^{+}$, as well as the overall branching fractions of the $B^{+}\to {\rho }^0{K}^{+}\gamma$, $B^{+}\to K^{*0}{\pi }^{+}\gamma$ and $S$-wave $B^{+}\to (K\pi {)}_0^{*0}{\pi }^{+}\gamma$ components. For events from the $\rho$ mass band, we measure the $CP$-violating parameters ${\mathcal{S}}_{K_S^0{\pi }^{+}{\pi }^{-}\gamma }=0.14\pm 0.25\pm 0.03$ and ${\mathcal{C}}_{K_S^0{\pi }^{+}{\pi }^{-}\gamma }=-0.39\pm 0.20_{-0.02}^{+0.03}$, where the first uncertainties are statistical and the second are systematic. We extract from this measurement the time-dependent $CP$ asymmetry related to the $CP$ eigenstate ${\rho }^0{K}_S^0$ and obtain ${\mathcal{S}}_{K_S^0\rho \gamma }=-0.18\pm 0.32_{-0.05}^{+0.06}$, which provides information on the photon polarization in the underlying $b\to s\gamma$ transition.

We investigate the Drude weight and the related Mazur-Suzuki (MS) bound in a broad variety of strongly coupled field theories with a gravity dual at finite temperature and chemical potential. We revisit the derivation of the recently proposed universal expression for the Drude weight for Einstein-Maxwell-dilaton (EMd) theories and extend it to the case of theories with multiple massless gauge fields. We show that the MS bound, which in the context of condensed matter provides information on the integrability of the theory, is saturated in these holographic theories including R-charged backgrounds. We then explore the limits of this universality by studying EMd theories with $U(1)$ spontaneous symmetry breaking and gravity duals of nonrelativistic field theories including an asymptotically Lifshitz EMd model with two massless gauge fields and the Einstein-Proca model. In all these cases, the Drude weight, computed analytically, deviates from the universal result and the MS bound is not saturated. In general, it is not possible to deduce the low temperature dependence of the Drude weight by simple dimensional analysis. Finally, we study the effect of a weak breaking of translational symmetry by coupling the EMd action, with and without $U(1)$ spontaneous symmetry breaking, to an axion field. We show that the coherent part of the conductivity in this limit is simply the product of the MS bound and the scattering time obtained from the leading quasinormal mode. For asymptotically AdS theories it seems that the MS bound sets a lower bound on the dc conductivity for a given scattering time.

We use compatibility of the second fundamental form corrections to Dirac-Born-Infeld action at order ${\alpha }^{\prime 2}$ which includes the trace of the second fundamental form, with T-duality and with the linear S-duality as guiding principles, to find an off-shell D-brane action at order ${\alpha }^{\prime 2}$ in type II superstring theories in flat spcetime.

A scenario of moduli stabilization based on the interplay between closed and open string sectors is explored in a bottom-up approach. We study $\mathcal{N}=1$ effective supergravities inspired by type IIB orientifold constructions that include background fluxes and nonperturbative effects. The former generate the standard flux superpotential for the axiodilaton and complex structure moduli. The latter can be induced by gaugino condensation in a non-Abelian sector of D7-branes and involve the overall Kähler modulus of the compactification as well as matter fields. We analyze the dynamics of this coupled system and show that it is compatible with single-step moduli stabilization in a metastable de Sitter vacuum. A novelty of the scenario is that the F-term potential suffices to generate a positive cosmological constant and to stabilize all moduli, except for a flat direction that can be either lifted by a mass term or eaten up by an anomalous U(1).

A novel scenario for the emergence of geometry in random multitrace matrix models of a single Hermitian matrix $M$ with unitary $U(N)$ invariance, i.e. without a kinetic term, is presented. In particular, the dimension of the emergent geometry is determined from the critical exponents of the disorder-to-uniform-ordered transition, whereas the metric is determined from the Wigner semicircle law behavior of the eigenvalues distribution of the matrix $M$. If the uniform ordered phase is not sustained in the phase diagram, then there is no emergent geometry in the multitrace matrix model.

We discuss how nonrelativistic spacetime symmetries can be gauged in the context of the coset construction. We consider theories invariant under the centrally extended Galilei algebra as well as the Lifshitz one, and we investigate under what conditions they can be supplemented by scale transformations. We also clarify the role of torsion in these theories.

We analyze spherically symmetric black hole solutions with time-dependent scalar hair in a class of Lovelock-Galileon theories, which are the scalar-tensor theories with second-order field equations in arbitrary dimensions. We first show that known black hole solutions in five dimensions are always plagued by the ghost/gradient instability in the vicinity of the horizon. We then generalize such black hole solutions to higher dimensions and show that the same instability found in five dimensions appears universally in any number of dimensions.

We study a model for quantum lightcone fluctuations in which vacuum fluctuations of the electric field and of the squared electric field in a nonlinear dielectric material produce variations in the flight times of probe pulses. When this material has a nonzero third order polarizability, the flight time variations arise from squared electric field fluctuations, and are analogous to effects expected when the stress tensor of a quantized field drives passive spacetime geometry fluctuations. We also discuss the dependence of the squared electric field fluctuations upon the geometry of the material, which in turn determines a sampling function for averaging the squared electric field along the path of the pulse. This allows us to estimate the probability of especially large fluctuations, which is a measure of the probability distribution for quantum stress tensor fluctuations.

Scalar and gravitational perturbations on Kerr–anti–de Sitter (Kerr-AdS) black holes have been addressed in the literature and have been shown to exhibit a rich phenomenology. In this paper, we complete the analysis of bosonic fields on this background by studying Maxwell perturbations, focusing on superradiant instabilities and vector clouds. For this purpose, we solve the Teukolsky equations numerically, imposing the boundary conditions we have proposed in [1] for the radial Teukolsky equation. As found therein, two Robin boundary conditions can be imposed for Maxwell fields on Kerr-AdS black holes, one of which produces a new set of quasinormal modes even for Schwarzschild-AdS black holes. Here, we show these different boundary conditions produce two different sets of superradiant modes. Interestingly, the “new modes” may be unstable in a larger parameter space. We then study stationary Maxwell clouds that exist at the threshold of the superradiant instability, with the two Robin boundary conditions. These clouds, obtained at the linear level, indicate the existence of a new family of black hole solutions at the nonlinear level, within the Einstein-Maxwell-AdS system, branching off from the Kerr-Newman-AdS family. As a comparison with the Maxwell clouds, scalar clouds on Kerr-AdS black holes are also studied, and it is shown there are Kerr-AdS black holes that are stable against scalar, but not vector, modes with the same “quantum numbers”.