In this paper, we explore the nucleation of vacuum bubbles in the Brans-Dicke type theory of gravity. In the Euclidean signature, we evaluate the fields at the vacuum bubbles as solutions of the Euler-Lagrange equations of motion as well as the bubble nucleation probabilities by integrating the Euclidean action. We illustrate three possible ways to obtain vacuum bubbles: true vacuum bubbles for $\omega >-3/2$, false vacuum bubbles for $\omega <-3/2$, and false vacuum bubbles for $\omega >-3/2$ when the vacuum energy of the false vacuum in the potential of the Einstein frame is less than that of the true vacuum. After the bubble is nucleated at the $t=0$ surface, we can smoothly interpolate the field combinations to some solutions in the Lorentzian signature and consistently continue their subsequent evolutions. Therefore, we conclude that, in general scalar-tensor theories like this Brans-Dicke type theories, which may include and represent certain features of string theory, vacuum bubbles come in false vacuum bubbles as well as in true vacuum bubbles, as long as a special condition is assumed on the potential.

We present the first search for the decay $D_s^{+}\to \omega e^{+}\nu$ to test the four-quark content of the $D_s^{+}$ and the $\omega \mathrm{\text{−}}\varphi$ mixing model for this decay. We use $586{\mathrm{pb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at a center-of-mass energy of 4170 MeV. We find no evidence of a signal, and set an upper limit on the branching fraction of $\mathcal{B}(D_s^{+}\to \omega e^{+}\nu )<0.20\%$ at the 90% confidence level.

We consider probe Dp-branes, $p=3$, 5, 7, in global ${\mathrm{AdS}}_5\times S^5$, rotating along an internal direction in the $S^5$. These are dual to strongly interacting $\mathcal{N}=4$ super Yang-Mills on $S^3$ with massless fundamental flavors, in the presence of an $R$-symmetry chemical potential for flavor fermions. For massless, “anti de Sitter-filling” Dp-brane embeddings at zero temperature, we find an infinite set of threshold values of the chemical potential at which instabilities are triggered. The onset of instability is always preceded by metastability of the zero-density state. From the onset values of the chemical potential, we infer that unstable directions favor a homogeneous condensate of a bilinear made from fermion harmonics, or Cooper pairing. We confirm this picture both numerically and analytically. The linearized analysis showing the appearance of instabilities involves a charged scalar in global anti de Sitter space coupled to a (large) constant background gauge potential. The resulting frequency space correlator of the fermion bilinear at strong coupling displays poles in the upper half plane. In contrast, the correlator at zero coupling exhibits Pauli blocking due to occupation of states below the Fermi level, but no instabilities. The end point of the strong coupling instability is not visible in our setup.

Recently, André Martin has proved a rigorous upper bound on the inelastic cross section${\sigma }_{\mathrm{inel}}$ at high energy, which is one-fourth of the known Froissart-Martin-Lukaszuk upper bound on ${\sigma }_{\mathrm{tot}}$. Here, we obtain an upper bound on ${\sigma }_{\mathrm{inel}}$ in terms of ${\sigma }_{\mathrm{tot}}$ and show that the Martin bound on ${\sigma }_{\mathrm{inel}}$ is improved significantly with this added information.

We study the effect of black hole spin on the accuracy of the post-Newtonian approximation. We focus on the gravitational energy flux for the quasicircular, equatorial, extreme mass-ratio inspiral of a compact object into a Kerr black hole of mass $M$ and spin $J$. For a given dimensionless spin $a\equiv J/M^2$ (in geometrical units $G=c=1$), the energy flux depends only on the orbital velocity $v$ or (equivalently) on the Boyer-Lindquist orbital radius $r$. We investigate the formal region of validity of the Taylor post-Newtonian expansion of the energy flux (which is known up to order $v^8$ beyond the quadrupole formula), generalizing previous work by two of us. The error function used to determine the region of validity of the post-Newtonian expansion can have two qualitatively different kinds of behavior, and we deal with these two cases separately. We find that, at any fixed post-Newtonian order, the edge of the region of validity (as measured by $v/v_{\mathrm{ISCO}}$, where $v_{\mathrm{ISCO}}$ is the orbital velocity at the innermost stable circular orbit) is only weakly dependent on $a$. Unlike in the nonspinning case, the lack of sufficiently high-order terms does not allow us to determine if there is a convergent to divergent transition at order $v^6$. Independent of $a$, the inclusion of angular multipoles up to and including $\ell =5$ in the numerical flux is necessary to achieve the level of accuracy of the best-known ($N=8$) post-Newtonian expansion of the energy flux.

The energy density of relic gravitational waves (GWs) emitted by primordial black holes (PBHs) is calculated. We estimate the intensity of GWs produced at quantum and classical scattering of PBHs, the classical graviton emission from the PBH binaries in the early Universe, and the graviton emission due to PBH evaporation. If nonrelativistic PBHs dominated the cosmological energy density prior to their evaporation, the probability of formation of dense clusters of PBHs and their binaries in such clusters would be significant and the energy density of the generated gravitational waves in the present-day universe could exceed that produced by other known mechanisms. The intensity of these gravitational waves would be maximal in the GHz frequency band of the spectrum or higher and makes their observation very difficult by present detectors but also gives a rather good possibility to investigate it by present and future high-frequency gravitational waves electromagnetic detectors. However, the low-frequency part of the spectrum in the range $f\sim 0.1–10\mathrm{Hz}$ may be detectable by the planned space interferometers DECIGO/BBO. For sufficiently long duration of the PBH matter-dominated stage, the cosmological energy fraction of GWs from inflation would be noticeably diluted.

We investigate the gravitational radiation emitted by an isolated system for gravity theories with Lagrange density $f(R)=R+a{R}^2$. As a formal result, we obtain leading order corrections to the quadrupole formula in general relativity. We make use of the analogy of $f(R)$ theories with scalar-tensor theories, which in contrast to general relativity feature an additional scalar degree of freedom. Unlike general relativity, where the leading order gravitational radiation is produced by quadrupole moments, the additional degree of freedom predicts gravitational radiation of all multipoles, in particular, monopoles and dipoles, as this is the case for the most alternative gravity theories known today. An application to a hypothetical binary pulsar moving in a circular orbit yields the rough limit $a\lesssim 1.7\times {10}^{17}{\mathrm{m}}^2$ by constraining the dipole power to account at most for 1% of the quadrupole power as predicted by general relativity.

Coherent elastic neutrino-nucleus and weakly interacting massive particle-nucleus interaction signatures are expected to be quite similar. This paper discusses how a next-generation ton-scale dark matter detector could discover neutrino-nucleus coherent scattering, a precisely-predicted standard model process. A high-intensity pion- and muon- decay-at-rest neutrino source recently proposed for oscillation physics at underground laboratories would provide the neutrinos for these measurements. In this paper, we calculate raw rates for various target materials commonly used in dark matter detectors and show that discovery of this interaction is possible with a $2\mathrm{ton}·\mathrm{year}$ GEODM exposure in an optimistic energy threshold and efficiency scenario. We also study the effects of the neutrino source on weakly interacting massive particle sensitivity and discuss the modulated neutrino signal as a sensitivity/consistency check between different dark matter experiments at the Deep Underground Science and Engineering Laboratory. Furthermore, we consider the possibility of coherent neutrino physics with a GEODM module placed within tens of meters of the neutrino source.

We study the processes $\gamma \gamma \to K_S^0{K}^{\pm }{\pi }^{\mp }$ and $\gamma \gamma \to K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}{\pi }^0$ using a data sample of $519.2{\mathrm{fb}}^{-1}$ recorded by the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider at center-of-mass energies near the ${\rm Y}(nS)$ ($n=2$, 3, 4) resonances. We observe the ${\eta }_c(1S)$, ${\chi }_{c0}(1P)$ and ${\eta }_c(2S)$ resonances produced in two-photon interactions and decaying to $K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}{\pi }^0$, with significances of 18.1, 5.4 and 5.3 standard deviations (including systematic errors), respectively, and report $4.0\sigma$ evidence of the ${\chi }_{c2}(1P)$ decay to this final state. We measure the ${\eta }_c(2S)$ mass and width in $K_S^0{K}^{\pm }{\pi }^{\mp }$ decays, and obtain the values $m({\eta }_c(2S))=3638.5\pm 1.5\pm 0.8\mathrm{MeV}/c^2$ and $\Gamma ({\eta }_c(2S))=13.4\pm 4.6\pm 3.2\mathrm{MeV}$, where the first uncertainty is statistical and the second is systematic. We measure the two-photon width times branching fraction for the reported resonance signals, and search for the ${\chi }_{c2}(2P)$ resonance, but no significant signal is observed.

We extend our previous work on the functional approach to the dynamical Casimir effect, to compute dissipative effects due to the relative motion of two flat, parallel, imperfect mirrors in vacuum. The interaction between the internal degrees of freedom of the mirrors and the vacuum field is modeled with a nonlocal term in the vacuum field action. We consider two different situations: either the motion is “normal,” i.e., the mirrors advance or recede changing the distance $a(t)$ between them; or it is “parallel,” namely, $a$ remains constant, but there is a relative sliding motion of the mirrors’ planes. For the latter, we show explicitly that there is a nonvanishing frictional force, even for a constant shifting speed.

We canonically quantize the Proca field in the Rindler wedge and compute the total response rate of a uniformly accelerated current interacting with massive vector Rindler particles from the Unruh thermal bath. We explicitly verify that the result obtained is exactly the same as the emission rate of massive vector particles in the Minkowski vacuum as analyzed by inertial observers. Eventually, our results are interpreted in terms of the interaction of static electrons coupled to $Z^0$ bosons present in Hawking radiation close to the event horizon of a black hole.

We analyze, starting from first principles, the quantization of field theories, in order to find out to which problems a noncommutative time would possibly lead. We examine the problem in the interaction picture (Tomonaga-Schwinger equation), the Heisenberg picture (Yang-Feldman-Källén equation), and the path integral approach. They all indicate inconsistency when time is taken as a noncommutative coordinate. The causality issue appears as the key aspect, while the unitarity problem is subsidiary. These results are consistent with string theory, which does not admit a time-space noncommutative quantum field theory as its low-energy limit, with the exception of lightlike noncommutativity.

Using the generalized Schwinger-DeWitt technique, we calculate the divergent part of the one-loop effective action for gravity nonminimally coupled to a multiplet of scalar fields. All the calculations are consistently done in the Jordan frame.

We discuss the dynamics of the Dirac fermions in the general strong gravitational and electromagnetic fields. We derive the general Hermitian Dirac Hamiltonian and transform it to the Foldy-Wouthuysen representation for the spatially isotropic metric. The quantum operator equations of motion are obtained and the semiclassical limit is analyzed. The comparison of the quantum mechanical and classical equations shows their complete agreement. The helicity dynamics in strong fields is discussed. Squaring the covariant Dirac equation explicitly shows a similarity of the interactions of electromagnetic and gravitational fields with a charged and spinning particle.

Simultaneous gravitational and electromagnetic wave observations of merging black hole binaries (BHBHs) can provide unique opportunities to study gravitation physics, accretion, and cosmology. Here we perform fully general-relativistic, hydrodynamic simulations of equal-mass, nonspinning BHBHs coalescing in a circumbinary disk. We evolve the metric using the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of Einstein’s field equations with standard moving puncture gauge conditions. We handle the hydrodynamics via a high-resolution shock-capturing scheme. These initial simulations are exploratory in nature and simplified accordingly. We track the inspiral starting from a binary separation of $10M$, where $M$ is the total binary mass. We take the disks to have an inner radius at $R_{\mathrm{in}}\approx 15M$ to account for the hollow created by the binary torques. Our disks extend to $R\approx 65M$ and have an initial scale height of $H/R\approx 0.03–0.11$. The gas is governed by a $\Gamma$-law equation of state, with $\Gamma$ equal to $5/3$, $4/3$, and 1.1. Disks are allowed to relax in the “early inspiral” epoch to provide quasistationary realistic initial data. We then evolve the spacetime metric and matter during the “late inspiral and merger” epochs. The later simulations are designed to track BHBH inspiral following disk-binary decoupling, through merger and ringdown, terminating before viscosity has time to fill the hollow about the black hole remnant. We compute the gas flow and accretion rate and estimate the electromagnetic luminosity due to bremsstrahlung and synchrotron emission as a perturbation for optically thin disks. The synchrotron component of the luminosity peaks in the infrared band and should be detectable by WFIRST and possibly the LSST for a ${10}^8{M}_{\odot }$ binary embedded in a disk with a density $n\sim {10}^{12}{\mathrm{cm}}^{-3}$ at $z=1$, beginning with a maximum value of $L\sim {10}^{46}{n}_{12}^2{M}_8^3\mathrm{erg}{\mathrm{s}}^{-1}$ at decoupling, and decreasing steadily over a time scale of $\sim 100M_8$ hours to a value of $L\sim {10}^{45}{n}_{12}^2{M}_8^3\mathrm{erg}{\mathrm{s}}^{-1}$ at merger.

We discuss present and future cosmological constraints on variations of the fine structure constant $\alpha$ induced by an early dark energy component having the simplest allowed (linear) coupling to electromagnetism. We find that current cosmological data show no variation of the fine structure constant at recombination with respect to the present-day value, with $\alpha /{\alpha }_0=0.975\pm 0.020$ at 95% C.L., constraining the energy density in early dark energy to ${\Omega }_e<0.060$ at 95% C.L. Moreover, we consider constraints on the parameter quantifying the strength of the coupling by the scalar field. We find that current cosmological constraints on the coupling are about 20 times weaker than those obtainable locally (which come from Equivalence Principle tests). However forthcoming or future missions, such as the Planck Surveyor and the CMBPol satellite, can match and possibly even surpass the sensitivity of current local tests.

Number counts of massive high-redshift clusters provide a window to study primordial non-Gaussianity. The current quality of data, however, forces the statistical analysis to probe a region of parameter space—the extreme tail of the mass function—which is neither accessible in any of the currently available theoretical prescriptions for calculating the mass function, nor calibrated in $N$-body simulations. In this work we present a new analytical prescription for calculating a resummed non-Gaussian halo mass function, which is constructed to remain stable in the extreme tail. We show that the prescription works well in the parameter regime that has been currently explored in simulations. We then use Fisher matrix techniques to compare our prescription with an extrapolated fit to $N$-body simulations, which has recently been used to obtain constraints from data collected by the South Pole Telecope. We show that for the current data, both prescriptions would lead to statistically consistent constraints. As the data improve, however, there is a possibility of introducing a statistically significant bias in the constraints due to the choice of prescription, especially if non-Gaussianity is scale dependent and becomes relatively large on cluster scales. It would then be necessary to test the accuracy of the prescriptions in $N$-body simulations that can probe clusters with high masses and redshifts in the presence of large non-Gaussianity.

We introduce a search method for a new class of gravitational-wave signals, namely, long-duration $\mathcal{O}(\mathrm{\text{hours-weeks}})$ transients from spinning neutron stars. We discuss the astrophysical motivation from glitch relaxation models and we derive a rough estimate for the maximal expected signal strength based on the superfluid excess rotational energy. The transient signal model considered here extends the traditional class of infinite-duration continuous-wave signals by a finite start-time and duration. We derive a multidetector Bayes factor for these signals in Gaussian noise using $\mathcal{F}$-statistic amplitude priors, which simplifies the detection statistic and allows for an efficient implementation. We consider both a fully coherent statistic, which is computationally limited to directed searches for known pulsars, and a cheaper semicoherent variant, suitable for wide parameter-space searches for transients from unknown neutron stars. We have tested our method by Monte-Carlo simulation, and we find that it outperforms orthodox maximum-likelihood approaches both in sensitivity and in parameter-estimation quality.

Mimicking pristine 2D graphene, we revisit the BBTW model for 4D lattice QCD given in [P. F. Bedaque et al., Phys. Rev. D 78, 017502 (2008)] by using the hidden $SU(5)$ symmetry of the 4D hyperdiamond lattice ${\mathcal{H}}_4$. We first study the link between the ${\mathcal{H}}_4$ and $SU(5)$; then we refine the BBTW 4D lattice action by using the weight vectors ${\lambda }_1$, ${\lambda }_2$, ${\lambda }_3$, ${\lambda }_4$, and ${\lambda }_5$ of the five-dimensional representation of $SU(5)$ satisfying $\sum _i{\lambda }_i=0$. After that, we study explicitly the solutions of the zeros of the Dirac operator $\mathcal{D}$ in terms of the $SU(5)$ simple roots ${\alpha }_1$, ${\alpha }_2$, ${\alpha }_3$, and ${\alpha }_4$ generating ${\mathcal{H}}_4$; and its fundamental weights ${\omega }_1$, ${\omega }_2$, ${\omega }_3$ ${\omega }_4$ which generate the reciprocal lattice ${\mathcal{H}}_4^{*}$. It is shown, among others, that these zeros live at the sites of ${\mathcal{H}}_4^{*}$; and the continuous limit $\mathcal{D}$ is given by $\frac{id\sqrt{5}}{2}$ ${\gamma }^{\mu }{\mathbf{k}}_{\mu }$ with $d$, ${\gamma }^{\mu }$, and ${\mathbf{k}}_{\mu }$ standing, respectively, for the lattice parameter of ${\mathcal{H}}_4$, the usual 4 Dirac matrices and the 4D wave vector. Other features, such as differences with BBTW model as well as the link between the Dirac operator following from our construction and the one suggested by Creutz using quaternions, are also given.