Masses and decay constants of the scalar quarkonia, ${\chi }_{Q0}(Q=b,c)$ with quantum numbers $I^G(J^{PC})=0^{+}(0^{++})$, are calculated in the framework of the QCD sum rules approach both in vacuum and finite temperature. The masses and decay constants remain unchanged up to $T\simeq 100\mathrm{MeV}$ but they start to diminish with increasing the temperature after this point. Near the critical or deconfinement temperature, the decay constants reach approximately to 25% of their values in vacuum, while the masses are decreased about 6% and 23% for bottom and charm cases, respectively. The results at zero temperature are consistent with the existing experimental values and predictions of the other nonperturbative approaches. Our predictions on the decay constants in vacuum, as well as the behavior of the masses and decay constants with respect to the temperature, can be checked in the future experiments.

We study chiral symmetry breaking for relativistic fermions, described by a parity-violating Lagrangian in $2+1$-dimensions, in the presence of a heat bath and a uniform external magnetic field. Working within their four-component formalism allows for the inclusion of both parity-even and -odd mass terms. Therefore, we can define two types of fermion antifermion condensates. For a given value of the magnetic field, there exist two different critical temperatures which would render one of these condensates identically zero, while the other would survive. Our analysis is completely general: it requires no particular simplifying hierarchy among the energy scales involved, namely, bare masses, field strength, and temperature. However, we do reproduce some earlier results, obtained or anticipated in literature, corresponding to special kinematical regimes for the parity conserving case. Relating the chiral condensate to the one-loop effective Lagrangian, we also obtain the magnetization and the pair production rate for different fermion species in a uniform electric field through the replacement $B\to -iE$.

We study extensions of the minimal supersymmetric standard model (MSSM) with new degrees of freedom that couple sizably to the MSSM Higgs sector and lie in the TeV range. After integrating out the physics at the TeV scale, the resulting Higgs spectrum can significantly differ from typical supersymmetric scenarios, thereby providing a window beyond the MSSM (BMSSM). Taking into account current LEP and Tevatron constraints, we perform an in-depth analysis of the Higgs collider phenomenology and explore distinctive characteristics of our scenario with respect to both the standard model and the MSSM. We propose benchmark scenarios to illustrate specific features of BMSSM Higgs searches at the Tevatron and the LHC.

Recent experimental results indicate that the dark matter sector may have a nonminimal structure with a spectrum of states and interactions. Inelastic scattering has received particular attention in light of DAMA’s annual modulation signal. Composite inelastic dark matter (CiDM) provides a dynamical origin for the mass splittings in inelastic dark matter models. We show that higher dimensional operators in the CiDM Lagrangian lead to an admixture of inelastic and elastic scattering in the presence of parity violation. This scenario is consistent with direct detection experiments, even when parity violation is nearly maximal. We present an effective field theory description of such models and discuss the constraints from direct detection experiments. The CiDM model with parity violation has nontrivial phenomenology because of the multiple scattering channels that are allowed.

We present improved measurements of the branching fractions for the decays $B^0\to D_s^{+}{\pi }^{-}$ and ${\overline{B}}^0\to D_s^{+}{K}^{-}$ using a data sample of $657\times {10}^6$ $B\overline{B}$ events collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The results are $\mathcal{B}(B^0\to D_s^{+}{\pi }^{-})=(1.99\pm 0.26\pm 0.18)\times {10}^{-5}$ and $\mathcal{B}({\overline{B}}^0\to D_s^{+}{K}^{-})=(1.91\pm 0.24\pm 0.17)\times {10}^{-5}$, where the uncertainties are statistical and systematic, respectively. Based on these results, we determine the ratio between amplitudes of the doubly Cabibbo suppressed decay $B^0\to D^{+}{\pi }^{-}$ and the Cabibbo favored decay $B^0\to D^{-}{\pi }^{+}$, $R_{D\pi }=[1.71\pm 0.11(\mathrm{stat})\pm 0.09(\mathrm{syst})\pm 0.02(\mathrm{theo})]\%$, where the last term denotes the theory error.

In $2+1$ dimensions at finite temperature, spontaneous symmetry breaking of global symmetries is precluded by large thermal fluctuations of the order parameter. The holographic correspondence implies that analogous effects must also occur in $3+1$ dimensional theories with gauged symmetries in certain curved spacetimes with horizon. By performing a one loop computation in the background of a holographic superconductor, we show that bulk quantum fluctuations wash out the classical order parameter at sufficiently large distance scales. The low temperature phase is seen to exhibit algebraic long-range order. Beyond the specific example we study, holography suggests that IR singular quantum fluctuations of the fields and geometry will play an interesting role for many $3+1$ dimensional asymptotically anti–de Sitter spacetimes with planar horizon.

In this paper the Casimir energy of two parallel plates made by materials of different penetration depth and no medium in between is derived. We study the Casimir force density and derive analytical constraints on the two penetration depths which are sufficient conditions to ensure repulsion. Compared to other methods our approach needs no specific model for dielectric or magnetic material properties and constitutes a complementary analysis.

We give a theoretical framework to obtain a low-energy effective theory of quantum chromodynamics (QCD) towards a first-principle derivation of confinement/deconfinement and chiral-symmetry breaking/restoration crossover transitions. In fact, we demonstrate that an effective theory obtained using simple but nontrivial approximations within this framework enables us to treat both transitions simultaneously on equal footing. A resulting effective theory is regarded as a modified and improved version of nonlocal Polyakov-loop extended Nambu-Jona-Lasinio (nonlocal PNJL) models proposed recently by Hell, Rössner, Cristoforetti, and Weise, and Sasaki, Friman, and Redlich, extending the original (local) PNJL model by Fukushima and others. A novel feature is that the nonlocal NJL coupling depends explicitly on the temperature and Polyakov loop, which affects the entanglement between confinement and chiral-symmetry breaking, together with the cross term introduced through the covariant derivative in the quark sector considered in the conventional PNJL model. The chiral-symmetry breaking/restoration transition is controlled by the nonlocal NJL interaction, while the confinement/deconfinement transition in the pure gluon sector is specified by the nonperturbative effective potential for the Polyakov loop obtained recently by Braun, Gies, Marhauser, and Pawlowski. The basic ingredients are a reformulation of QCD based on new variables and the flow equation of the Wetterich type in the Wilsonian renormalization group. This framework can be applied to investigate the QCD phase diagram at finite temperature and density.

We consider a Lorentz-violating theory of inflation consisting of Einstein-aether theory with a scalar inflaton coupled bilinearly to the expansion of the aether. We determine the conditions for linearized stability, positive energy, and vanishing of preferred-frame post-Newtonian parameters, and find that all these conditions can be met. In homogeneous and isotropic cosmology, the inflaton-aether expansion coupling leads to a driving force on the inflaton that is proportional to the Hubble parameter. This force affects the slow-roll dynamics, but still allows for a natural end to inflation.

We use analytic calculations of the post-recombination gravitational effects of cosmic strings to estimate the resulting CMB power spectrum, bispectrum and trispectrum. We place a particular emphasis on multipole regimes relevant for forthcoming CMB experiments, notably the Planck satellite. These calculations use a flat-sky approximation, generalizing previous work by integrating string contributions from last scattering to the present day, finding the dominant contributions to the correlators for multipoles $l>50$. We find a well-behaved shape for the string bispectrum (without divergences) which is easily distinguishable from the inflationary bispectra which possess significant acoustic peaks. We estimate that the nonlinearity parameter characterizing the bispectrum is approximately $0\gtrsim f_{\mathrm{NL}}\gtrsim -40$ (given present string constraints from the CMB power spectrum). We also apply these unequal time correlator methods to calculate the trispectrum for parrallelogram configurations, again valid over a large range of angular scales relevant for WMAP and Planck, as well as on very small angular scales. We find that, unlike the bispectrum which is suppressed by symmetry considerations, the trispectrum for cosmic strings is large. Our current estimate for the trispectrum parameter is ${\tau }_{\mathrm{NL}}\sim {10}^5$, which may provide one of the strongest constraints on the string model in future analysis.

In this paper, we explore the decay ${\eta }_b\to {\tau }^{+}{\tau }^{-}$ as a probe for a light pseudoscalar or a light axial vector state. We estimate the standard model branching ratio for this decay to be $\sim 4\times {10}^{-9}$. We show that considerably larger branching ratios, up to the present experimental limit of $\sim 8\%$, are possible in models with a light pseudoscalar or a light axial vector state. As we do not include possible mixing effects between the light pseudoscalar and the ${\eta }_b$, our results should be reliable when the pseudoscalar mass is away from the ${\eta }_b$ mass.

In this work, we investigate the rescattering effects in the radiative decay ${\rm Y}(5S)\to {\eta }_b+\gamma$, which were suggested to be crucially important for understanding the anomalous largeness of the branching ratios $B({\rm Y}(5S)\to {\rm Y}(1S)+\pi \pi )$ and $B({\rm Y}(5S)\to {\rm Y}(1S)+\eta )$. Our calculations show that the rescattering effects may enhance $\Gamma ({\rm Y}(10860)\to {\eta }_b+\gamma )$ by four orders, but the tetraquark structure does not. Recently the BABAR and CLEO collaborations have measured the mass of ${\eta }_b$ and the branching ratios $\mathcal{B}({\rm Y}(2S)\to {\eta }_b+\gamma )$, $\mathcal{B}({\rm Y}(3S)\to {\eta }_b+\gamma )$. We hope that very soon, ${\rm Y}(10860)\to {\eta }_b+\gamma$ will be measured and it would be an ideal opportunity for testing whether the rescattering or the tetraquark structure is responsible for the anomaly of $\mathcal{B}({\rm Y}(5S)\to {\rm Y}(nS){\pi }^{+}{\pi }^{-}(n=1,2,3))$, i.e., the future measurements on the radiative decays of ${\rm Y}(5S)$ might be a touchstone of the two mechanisms.

The scalar productions in heavy meson decays can provide a good platform to study not only heavy flavor physics but also their own physical properties in a dramatically different way. In this work, based on the assumption of two-quark structure of the scalars, the charmless hadronic $B_c\to SP,SV$ decays (here, $S$, $P$, and $V$ denote the light scalar, pseudoscalar, and vector mesons, respectively) are investigated by employing the perturbative QCD (pQCD) factorization approach. In the standard model all these considered $B_c$ meson decays can only occur through the annihilation diagrams. From our numerical evaluations and phenomenological analysis, we find that (a) the pQCD predictions for the $CP$-averaged branching ratios (BRs) of the considered $B_c$ decays vary in the range of ${10}^{-5}$ to ${10}^{-8}$, which will be tested in the ongoing LHCb and forthcoming Super-B experiments, while the $CP$-violating asymmetries for these modes are absent naturally in the standard model because only one type tree operator is involved; (b) for $B_c\to SP,SV$ decays, the BRs of $\Delta S=0$ processes are basically much larger than those of $\Delta S=1$ as generally expected because the different Cabibbo-Kobayashi-Maskawa factors are involved; (c) analogous to $B\to K^{*}{\eta }^{(\prime )}$ decays, $\mathrm{Br}(B_c\to {\kappa }^{+}\eta )\sim 5\times \mathrm{Br}(B_c\to {\kappa }^{+}{\eta }^{\prime })$ in the pQCD approach, which can be understood by the constructive and destructive interference between the ${\eta }_q$ and ${\eta }_s$ contributions to the $B_c\to {\kappa }^{+}\eta$ and $B_c\to {\kappa }^{+}{\eta }^{\prime }$ decays, however, $\mathrm{Br}(B_c\to K_0^{*}(1430)\eta )$ is approximately equal to $\mathrm{Br}(B_c\to K_0^{*}(1430){\eta }^{\prime })$ in both scenarios because the factorizable contributions from the ${\eta }_s$ term play the dominant role in the considered two channels; (d) if $a_0(980)$ and $\kappa$ are the $q\overline{q}$ bound states, the pQCD predicted BRs for $B_c\to a_0(980)(\pi ,\rho )$ and $B_c\to \kappa K^{(*)}$ decays will be in the range of ${10}^{-6}\sim {10}^{-5}$, which are within the reach of the LHCb experiments and could be measured in the near future; and (e) for the $a_0(1450)$ and $K_0^{*}(1430)$ channels, the BRs for $B_c\to a_0(1450)(\pi ,\rho )$ and $B_c\to K_0^{*}(1430)K^{(*)}$ modes in the pQCD approach are found to be $(5\sim 47)\times {10}^{-6}$ and $(0.7–36)\times {10}^{-6}$, respectively. A measurement of them at the predicted level will favor the $q\overline{q}$ structure and help understand the physical properties of the scalars and the involved QCD dynamics in the modes, especially the reliability of the pQCD approach to these $B_c$ meson decays.

We study the holographic p-wave superconductors in a five-dimensional Gauss-Bonnet gravity with an SU(2) Yang-Mills gauge field. In the probe approximation, we find that when the Gauss-Bonnet coefficient grows, the condensation of the vector field becomes harder, both the perpendicular and parallel components, with respect to the direction of the condensation, of the anisotropic conductivity decrease. We also study the mass of the quasiparticle excitations, the gap frequency and the DC conductivities of the p-wave superconductor. All of them depend on the Gauss-Bonnet coefficient. In addition, we observe a strange behavior for the condensation and the relation between the gap frequency and the mass of quasiparticles when the Gauss-Bonnet coefficient is larger than $9/100$, which is the upper bound for the Gauss-Bonnet coefficient from the causality of the dual field theory.

The effects of a nonzero photon rest mass can be incorporated into electromagnetism in a simple way using the Proca equations. In this vein, two interesting implications regarding the possible existence of a massive photon in nature, i.e., tiny alterations in the known values of both the anomalous magnetic moment of the electron and the gravitational deflection of electromagnetic radiation, are utilized to set upper limits on its mass. The bounds obtained are not as stringent as those recently found; nonetheless, they are comparable to other existing bounds and bring new elements to the issue of restricting the photon mass.

During eternal inflation, a landscape of vacua can be populated by the nucleation of bubbles. These bubbles inevitably collide, and collisions sometimes displace the field into a new minimum in a process known as a classical transition. In this paper, we examine some new features of classical transitions that arise when gravitational effects are included. Using the junction condition formalism, we study the conditions for energy conservation in detail, and solve explicitly for the types of allowed classical transition geometries. We show that the repulsive nature of domain walls, and the de Sitter expansion associated with a positive energy minimum, can allow for classical transitions to vacua of higher energy than that of the colliding bubbles. Transitions can be made out of negative or zero energy (terminal) vacua to a de Sitter phase, restarting eternal inflation, and populating new vacua. However, the classical transition cannot produce vacua with energy higher than the original parent vacuum, which agrees with previous results on the construction of pockets of false vacuum. We briefly comment on the possible implications of these results for various measure proposals in eternal inflation.

We study supersymmetry of a self-isospectral one-gap Pöschl-Teller system in the light of a mirror symmetry that is based on spatial and shift reflections. The revealed exotic, partially broken, nonlinear supersymmetry admits seven alternatives for a grading operator. One of its local, first order supercharges may be identified as a Hamiltonian of an associated one-gap, nonperiodic Bogoliubov-de Gennes system. The latter possesses a nonlinear supersymmetric structure, in which any of the three nonlocal generators of a Clifford algebra may be chosen as the grading operator. We find that the supersymmetry generators for both systems are the Darboux-dressed integrals of a free spin-$1/2$ particle in the Schrödinger picture, or of a free massive Dirac particle. Nonlocal Foldy-Wouthuysen transformations are shown to be involved in the supersymmetric structure.

The $SU(2{)}_L\times SU(2{)}_R$ chiral quark model consisting of the $(\sigma ,\overrightarrow{\pi })$ meson multiplet and the constituent quarks propagating on the homogeneous background of a temporal gauge field is solved at finite temperature and quark baryon chemical potential ${\mu }_q$ using an expansion in the number of flavors $N_f$, both in the chiral limit and for the physical value of the pion mass. Keeping the fermion propagator at its tree level, several approximations to the pion propagator are investigated. These approximations correspond to different partial resummations of the perturbative series. Comparing their solution with a diagrammatically formulated resummation relying on a strict large-$N_f$ expansion of the perturbative series, one concludes that only when the local part of the approximated pion propagator resums infinitely many orders in $1/N_f$ of fermionic contributions a sufficiently rapid crossover transition at ${\mu }_q=0$ is achieved allowing for the existence of a tricritical point or a critical end point in the ${\mu }_q-T$ phase diagram. The renormalization and the possibility of determining the counterterms in the resummation provided by a strict large-$N_f$ expansion are investigated.

Research on extracting science from binary-black-hole (BBH) simulations has often adopted a “scattering matrix” perspective: given the binary’s initial parameters, what are the final hole’s parameters and the emitted gravitational waveform? In contrast, we are using BBH simulations to explore the nonlinear dynamics of curved spacetime. Focusing on the head-on plunge, merger, and ringdown of a BBH with transverse, antiparallel spins, we explore numerically the momentum flow between the holes and the surrounding spacetime. We use the Landau-Lifshitz field-theory-in-flat-spacetime formulation of general relativity to define and compute the density of field energy and field momentum outside horizons and the energy and momentum contained within horizons, and we define the effective velocity of each apparent and event horizon as the ratio of its enclosed momentum to its enclosed mass-energy. We find surprisingly good agreement between the horizons’ effective and coordinate velocities. During the plunge, the holes experience a frame-dragging-induced acceleration orthogonal to the plane of their spins and their infall (“downward”), and they reach downward speeds of order $1000\mathrm{km}/\mathrm{s}$. When the common apparent horizon forms (and when the event horizons merge and their merged neck expands), the horizon swallows upward field momentum that resided between the holes, causing the merged hole to accelerate in the opposite (“upward”) direction. As the merged hole and the field energy and momentum settle down, a pulsational burst of gravitational waves is emitted, and the merged hole has a final effective velocity of about $20\mathrm{km}/\mathrm{s}$ upward, which agrees with the recoil velocity obtained by measuring the linear momentum carried to infinity by the emitted gravitational radiation. To investigate the gauge dependence of our results, we compare generalized harmonic and Baumgarte-Shapiro-Shibata-Nakamura-moving-puncture evolutions of physically similar initial data; although the generalized harmonic and Baumgarte-Shapiro-Shibata-Nakamura-moving-puncture simulations use different gauge conditions, we find remarkably good agreement for our results in these two cases. We also compare our simulations with the post-Newtonian trajectories and near-field energy-momentum.