A recent paper by Kumar (2012) (hereafter K12) claimed that in a contracting model, described by perturbations around a collapsing Friedmann model containing dust or radiation, the perturbations can grow in such a way that the linearity conditions would become invalid. This conclusion is not correct due to the following facts: first, it is claimed that the linearity conditions are not satisfied, but nowhere in K12 the amplitudes of the perturbations were in fact estimated. Therefore, without such estimates, the only possible conclusion from this work is the well-known fact that the perturbations indeed grow during contraction, which, per se, does not imply that the linearity conditions become invalid. Second, some evaluations of the linearity conditions are incorrect because third-order terms, instead of the appropriate second-order ones, are mistakenly compared with first-order terms, yielding artificially fast growing conditions. Finally, it is claimed that the results of K12 are in sharp contrast with the results of the paper by Vitenti and Pinto-Neto (2012) (hereafter VPN12), because the former was obtained in a gauge-invariant way. However, the author of K12 did not realize that the evolution of the perturbations were also calculated in a gauge-invariant way in VPN12, but some of the linearity conditions which are necessary to check cannot be expressed in terms of gauge-invariant quantities. In the present work, the incorrect or incomplete statements of K12 are clarified and completed, and it is shown that all other correct results of K12 were already present in VPN12, whose conclusions remain untouched, namely, that cosmological perturbations of quantum mechanical origin in a bouncing model can remain in the linear regime all along the contracting phase and at the bounce itself for a wide interval of energy scales of the bounce, ranging from the nucleosynthesis energy scale up to a few orders of magnitude below the Planck energy.

We compute the effective-one-body predictions for the dynamical state (energy and angular momentum) of a nonspinning, coalescing binary black hole at merger. We compare these predictions to estimates of the dynamical state at merger inferred from numerical-relativity data. We find agreement at the per mil level between effective-one-body and numerical-relativity results. This gives a new confirmation of the ability of effective-one-body theory to accurately describe not only the gravitational wave emission but also the dynamics of binary black holes, even in the strong-gravitational-field regime. Our work also provides predictions (and analytical fits) for the final mass and the final spin of coalescing black holes for all mass ratios, as well as analytical fits for the losses of energy and angular momentum during ringdown.

We perform a model independent study of the neutrino momentum distribution at freeze-out, treating the freeze-out temperature as a free parameter. Our results imply that measurement of neutrino reheating, as characterized by the measurement of the effective number of neutrinos $N_{\nu }$, amounts to the determination of the neutrino kinetic freeze-out temperature within the context of the standard model of particle physics where the number of neutrino flavors is fixed and no other massless (fractional) particles arise. At temperatures on the order of the neutrino mass, we show how cosmic background neutrino properties, i.e., energy density, pressure, and particle density, are modified in a physically consistent way as a function of neutrino mass and $N_{\nu }$.

Entangled pseudoscalar neutral meson pairs have been used in studying $CP$ violation and searching for $CPT$ violation, but almost all the previous works concern the $C=-1$ entangled state. Here we consider the $C=+1$ entangled state of pseudoscalar neutral mesons, which is quite different from the $C=-1$ entangled state and provides complementary information on symmetry violating parameters. After developing a general formalism, we consider three kinds of decay processes, namely, semileptonic-semileptonic, hadronic-hadronic, and semileptonic-hadronic processes. For each kind of processes, we calculate the integrated rates of joint decays with a fixed time interval, as well as asymmetries defined for these joint rates of different channels. In turn, these asymmetries can be used to determine the four real numbers of the two indirect symmetry violating parameters, based on a general relation between the symmetry violating parameters and the decay asymmetries presented here. Various discussions are provided on indirect and direct violations and the violation of the $\mathrm{\Delta }\mathcal{F}=\mathrm{\Delta }Q$ rule, with some results presented as theorems.

We examine the consistency of light dark matter (DM) elastic scattering in CoGeNT, DAMA, and CDMS-silicon in light of constraints from XENON, CDMS, LUX, PICASSO and COUPP. We consider a variety of operators that have been employed to reconcile anomalies with constraints, including anapole, magnetic dipole, momentum-dependent, and isospin-violating DM. We find that elastic scattering through these alternative operators does not substantially reduce the tension between the signals and the null constraints for operators where at least two of the three purported signals map onto a common space in the DM mass-scattering cross-section plane. Taking a choice of the scintillation efficiency that lies at the $-1\sigma$ region of the Manzur et al. measurement relieves tension between signals and the LUX constraint—in particular for a magnetic dipole interaction and a xenophobic interaction (though for the latter the signal regions do not substantially overlap). We also find that modest changes in the halo model do not alter this result. We conclude that, even relaxing the assumption about the type of elastic scattering interaction and taking a conservative choice for the scintillation efficiency, LUX and the results from other null experiments remain in tension with a light DM elastic scattering explanation of direct detection anomalies.

Motivated by the latest LHC Higgs data, we calculate the new physics contributions to the Higgs decay channels of $h\to \gamma \gamma$, $Z\gamma$, $\tau \tau$, $W{W}^{*}$, and $Z{Z}^{*}$ in the left-right twin Higgs (LRTH) model, induced by the loops involving the heavy $T$ quark, the $W_H$ and ${\varphi }^{\pm }$ bosons that appeared in the LRTH model. We find that (a) for a standard-model-like Higgs boson around 125.5 GeV, the signal rates normalized to the corresponding standard model (SM) predictions are always suppressed when new physics contributions are taken into account and approach the SM predictions for a large scalar parameter $f$; and (b) the LRTH prediction for $R_{\gamma \gamma }$ agrees well with the CMS measurement $R_{\gamma \gamma }=0.77\pm 0.27$ at $1\sigma$ level but differs from the ATLAS result. The forthcoming precision measurement of the diphoton signal at the LHC can be a sensitive probe for the LRTH model.

We perform global fits to the moments of semileptonic $B$-decay distributions and extract $|V_{cb}|$, the heavy quark masses, and the nonperturbative parameters of the heavy quark expansion. We include next-to-next-to-leading-order perturbative corrections and recent determinations of the charm mass and discuss how they improve the precision of the global fit. In particular, using the $m_c$ determination of Chetyrkin et al. [Phys. Rev. D80, 074010 (2009)], we get $m_b^{\mathrm{kin}}=4.541(23)\mathrm{GeV}$ and $|V_{cb}|=(42.42\pm 0.86)\times {10}^{-3}$. We also discuss the implications of the new fits for the normalization of rare $B$ decays, the zero-recoil sum rule in $B\to D^{*}\ell \nu$, and the inclusive determination of $|V_{ub}|$.

The problem of vacuum instability and creation of pairs by external fields $SU(2)$ is studied. The effective mass operator has complex eigenvalues implying decay and pair creation. We consider a constant external chromoelectric field and find a region in the parameter space where the vaccum becomes unstable and decays in pairs. Although the calculation is done in $SU(2)$ color group it is also valid for $SU(3)$.

It has been pointed out recently that current low-energy constraints still allow for sizable flavor-changing decay rates of the 125 GeV boson into leptons, $h\to \tau \ell$ ($\ell =e$, $\mu$). In this work we discuss the role of hadronic $\tau$-lepton decays in probing lepton flavor violating couplings in the Higgs sector. At low energy, the effective Higgs coupling to gluons induced by heavy quarks contributes to hadronic $\tau$ decays, establishing a direct connection with the relevant process at the LHC, $pp(gg)\to h\to \tau \ell$. Semileptonic transitions like $\tau \to \ell \pi \pi$ are sensitive to flavor-changing scalar couplings, while decays such as $\tau \to \ell {\eta }^{(\prime )}$ probe pseudoscalar couplings, thus providing a useful low-energy handle to disentangle possible Higgs flavor violating signals at the LHC. As part of our analysis, we provide an appropriate description of all the relevant hadronic matrix elements needed to describe Higgs mediated $\tau \to \ell \pi \pi$ transitions, improving over previous treatments in the literature.

We have set a new upper limit on the stochastic gravitational-wave background using two prototype torsion-bar antennas (TOBAs). A TOBA is a low-frequency gravitational-wave detector with bar-shaped test masses rotated by the tidal force of gravitational waves. As a result of simultaneous 7-hour observations with TOBAs in Tokyo and Kyoto in Japan, our upper limit with a confidence level of 95% is ${\mathrm{\Omega }}_{\mathrm{gw}}{h}_0^2<1.9\times {10}^{17}$ at 0.035–0.830 Hz, where $h_0$ is the Hubble constant in units of $100\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ and ${\mathrm{\Omega }}_{\mathrm{gw}}$ is the gravitational-wave energy density per logarithmic frequency interval in units of the closure density. We successfully updated the upper limit and extended the explored frequency band.

We show that in generic isotropic holographic theories the longitudinal Langevin diffusion coefficient along the string motion is larger compared to that of the transverse direction. We argue that this is in general a universal relation and we derive the generic conditions in order to be satisfied. A way to violate the relation is to consider anisotropic gauge/gravity dualities. We give an explicit example of this violation where the noise along the transverse direction is larger than the noise occurring along the quark motion. Moreover, we derive the effective world-sheet temperature for any generic theory and then the conditions for negative excess noise. We argue that isotropic theories cannot have negative excess noise, and we additionally remark that these conditions are difficult to get satisfied, indicating positivity of the excess noise even in a large class of anisotropic holographic theories, implying a strong universal property.

We analyze the Weyl invariance constraints on higher spin vertex operators in open superstring theory describing massless higher spin gauge field excitations in $d$-dimensional space-time. We show that these constraints lead to low-energy equations of motion for higher spin fields in AdS space, with the leading-order $\beta$ function for the higher spin fields producing Fronsdal’s operator in ${\mathrm{AdS}}_{d+1}$, despite that the higher spin vertex operators are originally defined in flat background. The correspondence between the $\beta$ function in string theory and ${\mathrm{AdS}}_{d+1}$ Fronsdal operators in space-time is found to be exact for $d=4$, while for other space-time dimensions, it requires modifications of manifest expressions for the higher spin vertex operators. We argue that the correspondence considered in this paper is the leading order of a more general isomorphism between Vasiliev’s equations and equations of motion of extended open string field theory, generalized to include the higher spin operators.

We calculate the one-loop effective potential at finite temperature for the Horava- Lifshitz-like QED and Yukawa-like theories for arbitrary values of the critical exponent and the space-time dimension. Additional remarks on the zero temperature situation are also presented.

In a previous paper, we computed expressions for the Detweiler-Whiting singular field of point scalar, electromagnetic and gravitational charges following a geodesic of the Schwarzschild spacetime. We now extend this to the case of equatorial orbits in Kerr spacetime, using coordinate and covariant approaches to compute expansions of the singular field in scalar, electromagnetic and gravitational cases. As an application, we give the calculation of previously unknown mode-sum regularization parameters. We also propose a new application of high-order approximations to the singular field, showing how they may be used to compute $m$-mode regularization parameters for use in the $m$-mode effective source approach to self-force calculations.

The presence of compact extra dimensions in cosmological scenarios in the context of $f(T)$-like gravities is discussed. For the case of toroidal compactifications, the analysis is performed in an arbitrary number of extra dimensions. Spherical topologies for the extra dimensions are then carefully studied in six and seven spacetime dimensions, where the proper vielbein fields responsible for the parallelization process are found.

I consider the weak-field limit (WFL) of the bimetric, relativistic formulation of the modified Newtonian dynamics (BIMOND)—the lowest order in the small departures $h_{\mu \nu }=g_{\mu \nu }-{\eta }_{\mu \nu }$, ${\widehat{h}}_{\mu \nu }={\widehat{g}}_{\mu \nu }-{\eta }_{\mu \nu }$ from double Minkowski space-time. In particular, I look at propagating solutions, for a favorite subclass of BIMOND. The WFL splits into two sectors for two linear combinations, $h_{\mu \nu }^{\pm }$, of $h_{\mu \nu }$ and ${\widehat{h}}_{\mu \nu }$. The $h_{\mu \nu }^{+}$ sector is equivalent to the WFL of general relativity (GR), with its gauge freedom, and has the same vacuum gravitational waves. The $h_{\mu \nu }^{-}$ sector is fully nonlinear even for the weakest $h_{\mu \nu }^{-}$, and inherits none of the coordinate gauge freedom. The equations of motion are scale invariant in the deep-MOND limit of purely gravitational systems. In these last two regards, the BIMOND WFL is greatly different from that of other bimetric theories studied to date. Despite the strong nonlinearity, an arbitrary pair of harmonic GR wave packets of $h_{\mu \nu }$ and ${\widehat{h}}_{\mu \nu }$ moving in the same direction, is a solution of the (vacuum) BIMOND WFL.

In this paper we study a massless, minimally coupled scalar field in a Friedmann-Lemaître-Robertson-Walker space-time with periods of different constant deceleration parameter. We assume the Bunch-Davies vacuum during inflation and then use a sudden matching approximation to match it onto a radiation era and subsequently onto a matter era. We then proceed to calculate the one-loop energy-momentum tensor from the inflationary quantum vacuum fluctuations in different eras. The energy-momentum tensor has the form of an ideal (quantum) fluid, characterized by an equation of state. When compared with the background, far away from the matching the quantum energy density in the radiation era exhibits a contribution that grows logarithmically with the scale factor. In the matter era the ratio of the quantum to classical fluid settles eventually to a tiny constant, ${\rho }_q/\rho \simeq (\hslash H_0{)}^2/(4\pi m_{\mathrm{P}}^2{c}^4)\sim {10}^{-13}$ for a grand unified scale inflation. Curiously, the late time scaling of quantum fluctuations suggests that they contribute a little to the dark matter of the Universe, provided that it clusters as cold dark matter, which needs to be checked.

Black hole horizon sections, modeled as marginally outer trapped surfaces (MOTS), possess a notion of stability admitting a spectral characterization. Specifically, the “principal eigenvalue” ${\lambda }_o$ of the MOTS-stability operator (an elliptic operator on horizon sections) must be nonnegative. We discuss the expression of ${\lambda }_o$ for axisymmetric stationary black hole horizons and show that, remarkably, it presents the form of the Young-Laplace law for soap bubbles in equilibrium, if ${\lambda }_o$ is identified with a formal pressure difference between the inner and outer sides of the “bubble.” In this view, which endorses the existing fluid analogies for black hole horizons, MOTS-stability is interpreted as a consequence of a pressure increase in the black hole trapped region.

The waveform phase for a neutron star binary can be split into point-particle terms and finite-size terms (characterized by the Love number) that account for equation-of-state effects. The latter first enter at fifth post-Newtonian (5PN) order (i.e., proportional to the tenth power of the orbital velocity), but the former are only known completely to 3.5PN order, with higher-order terms only known to leading order in the mass ratio. We here find that not including point-particle terms at 4PN order to leading and first order in the mass ratio in the template model can severely deteriorate our ability to measure the equation of state. This problem can be solved if one uses numerical waveforms once their own systematic errors are under control.