Motivated by recently observed disagreements with the standard model predictions in $B$ decays, we study $b\to d$, $s$ transitions in an asymmetric class of $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$ models, with a simple one-parameter structure of the right-handed mixing matrix for the quarks, which obeys the constraints from kaon physics. We use experimental constraints on the branching ratios of $b\to s\gamma$, $b\to ce{\overline{\nu }}_e$, and $B_{d,s}^0-{\overline{B}}_{d,s}^0$ mixing to restrict the parameters of the model: $g_R/g_L$, $M_{W_2}$, $M_{H^{\pm }}$, $\tan \beta$ as well as the elements of the right-handed quark mixing matrix $V_{\mathrm{CKM}}^R$. We present a comparison with the more commonly used (manifest) left-right symmetric model. Our analysis exposes the parameters most sensitive to $b$ transitions and reveals a large parameter space where left- and right-handed quarks mix differently, opening the possibility of observing marked differences in behavior between the standard model and the left-right model.

The production rate and kinematics of photons produced in association with $Z$ bosons are studied using $2{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collision data collected at the Collider Detector at Fermilab. The cross section for $p\overline{p}\to {\ell }^{+}{\ell }^{-}\gamma +X$ (where the leptons $\ell$ are either muons or electrons with dilepton mass $M_{\ell \ell }>40\mathrm{GeV}/c^2$, and where the photon has transverse energy $E_T^{\gamma }>7\mathrm{GeV}$ and is well separated from the leptons) is $4.6\pm 0.2(\mathrm{stat})\pm 0.3(\mathrm{syst})\pm 0.3(\mathrm{lum})\mathrm{pb}$, which is consistent with standard model expectations. We use the photon $E_T$ distribution from $Z\gamma$ events where the $Z$ has decayed to ${\mu }^{+}{\mu }^{-}$, $e^{+}{e}^{-}$, or $\nu \overline{\nu }$ to set limits on anomalous (non standard model) trilinear couplings between photons and $Z$ bosons.

In a sample of $467\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II collider at SLAC we have observed the decay ${\overline{B}}^0\to {\mathit{\Lambda }}_c^{+}\overline{p}{\pi }^0$ and measured the branching fraction to be $(1.94\pm 0.17\pm 0.14\pm 0.50)\times {10}^{-4}$, where the uncertainties are statistical, systematic, and the uncertainty on the ${\mathit{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+}$ branching fraction, respectively. We determine an upper limit of $1.5\times {10}^{-6}$ at 90% C.L. for the product branching fraction $\mathcal{B}({\overline{B}}^0\to {\mathit{\Sigma }}_c^{+}(2455)\overline{p})\times \mathcal{B}({\mathit{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})$. Furthermore, we observe an enhancement at the threshold of the invariant mass of the baryon-antibaryon pair.

We present a new analytical solution of the Einstein field equations describing a wormhole shell of zero thickness joining two Lemaître-Tolman-Bondi universes, with no radial accretion. The material on the shell satisfies the energy conditions and, at late times, the shell becomes comoving with the dust-dominated cosmic substratum.

This work discusses gravothermal catastrophe in astrophysical systems and provides an analytic collapse solution which exhibits many of the catastrophe properties. The system collapses into a trapped surface with outgoing energy radiated to a future boundary and provides an example of catastrophic collapse.

Exact nonstatic spherically symmetric black-hole solutions of the higher dimensional Einstein-Yang-Mills equations for a null dust with Yang-Mills gauge charge are obtained by employing Wu-Yang ansatz, namely, HD-EYM Vaidya solution. It is interesting to note that gravitational contribution of Yang-Mills (YM) gauge charge for this ansatz is indeed opposite (attractive rather than repulsive) that of Maxwell charge. It turns out that the gravitational collapse of null dust with YM gauge charge admits strong curvature shell focusing naked singularities violating cosmic censorship. However, there is significant shrinkage of the initial data space for a naked singularity of the HD-Vaidya collapse due to presence of YM gauge charge. The effect of YM gauge charge on structure and location of the apparent and event horizons is also discussed.

We consider the thermodynamics of chiral models in the mean-field approximation and discuss the relevance of the (frequently omitted) fermion vacuum loop. Within the chiral quark-meson model and its Polyakov loop extended version, we show that the fermion vacuum fluctuations can change the order of the phase transition in the chiral limit and strongly influence physical observables. We compute the temperature-dependent effective potential and baryon-number susceptibilities in these models, with and without the vacuum term, and explore the cutoff and the pion mass dependence of the susceptibilities. Finally, in the renormalized model the divergent vacuum contribution is removed using dimensional regularization.

We argue that in models of inflation with two scalar fields and noncanonical kinetic terms there is a possibility of obtaining a red tilt of the power spectrum of curvature perturbations from noncanonicality-induced interactions between the curvature and isocurvature perturbations. We describe an extremely simple model realizing this idea, study numerically its predictions for the perturbations, and discuss applications in realistic scenarios of inflation. We discuss to what extent in this model the scale of the inflationary potential can be decoupled from the amplitude of the density fluctuations.

Using the anti-de Sitter conformal theory correspondence, we examine holographic renormalization group flows in a framework where the bulk gravity contains higher curvature interactions. This holographic model allows us to distinguish the flow of the different central charges in dual theory. For example, in four dimensions, one finds that the flow of the central charge $a$ is naturally monotonic but that of $c$ is not. Our results agree with Cardy’s proposal to extend Zamolodchikov’s c-theorem to higher dimensions. We are also led to formulate a novel c-theorem for a universal coefficient appearing in the entanglement entropy of the fixed point conformal theories in any (including an odd) number of dimensions.

We study the path integral over reparametrizations that has been proposed as an ansatz for the Wilson loops in the large-$N$ QCD and reproduces the area law in the classical limit of large loops. We show that a semiclassical expansion for a rectangular loop captures the Lüscher term associated with $d=26$ dimensions and propose a modification of the ansatz that reproduces the Lüscher term in other dimensions, which is observed in lattice QCD. We repeat the calculation for an outstretched ellipse advocating the emergence of an analog of the Lüscher term and verify this result by a direct computation of the determinant of the Laplace operator and the conformal anomaly.

We consider the dimensional reductions of $\mathcal{N}=4$ supersymmetric Yang-Mills theory on $\mathbb{R}\times S^3$ to the three-dimensional theory on $\mathbb{R}\times S^2$, the orbifolded theory on $\mathbb{R}\times S^3/{\mathbb{Z}}_k$, and the plane-wave matrix model. With explicit emphasis on the three-dimensional theory, we demonstrate the realization of the $SU(2|3)$ algebra in a radial Hamiltonian framework. Using this structure we constrain the form of the spin chains, their $S$ matrices, and the corresponding one- and two-loop Hamiltonians of the three-dimensional theory, and find putative signs of integrability up to the two-loop order. The string duals of these theories admit the IIA plane-wave geometry as their Penrose limit. Using known results for strings quantized on this background, we explicitly construct the strong-coupling dual extended $SU(2|2)$ algebra and discuss its implications for the gauge theories.

A $\Lambda \mathrm{CDM}$ model with dark matter that decays into inert relativistic energy on a time scale longer than the Hubble time will produce an expansion history that can be misinterpreted as stable dark matter with time-varying dark energy. We calculate the corresponding spurious equation of state parameter, ${\tilde{w}}_{\varphi }$, as a function of redshift, and show that the evolution of ${\tilde{w}}_{\varphi }$ depends strongly on the assumed value of the dark-matter density, erroneously taken to scale as $a^{-3}$. Depending on the latter, one can obtain models that mimic quintessence (${\tilde{w}}_{\varphi }>-1$), phantom models (${\tilde{w}}_{\varphi }<-1$), or models in which the equation of state parameter crosses the phantom divide, evolving from ${\tilde{w}}_{\varphi }>-1$ at high redshift to ${\tilde{w}}_{\varphi }<-1$ at low redshift. All of these models generically converge toward ${\tilde{w}}_{\varphi }\approx -1$ at the present. The degeneracy between the $\Lambda \mathrm{CDM}$ model with decaying dark matter and the corresponding spurious quintessence model is broken by the growth of density perturbations.

We have a well-known equation in cosmological perturbation theory which appeared only by several simple algebraic errors made in many textbooks. There have been attempts to modify Newtonian equations aiming to reproduce that incorrect equation. We clarify why such attempts are wrong, present the correct equation to try in the modification, and explain its own limitation as well. We show that any form of density perturbation equation is possible by a suitable gauge condition.

The Aragats Space Environmental Center facilities continuously measure fluxes of neutral and charged secondary cosmic ray incidents on the Earth’s surface. Since 2003 in the 1-minute time series we have detected more than 100 enhancements in the electron, gamma ray, and neutron fluxes correlated with thunderstorm activities. During the periods of the count rate enhancements, lasting tens of minutes, millions of additional particles were detected. Based on the largest particle event of September 19, 2009, we show that our measurements support the existence of long-lasting particle multiplication and acceleration mechanisms in the thunderstorm atmosphere. For the first time we present the energy spectra of electrons and gamma rays from the particle avalanches produced in the thunderstorm atmosphere, reaching the Earth’s surface.

We calculate the decay rate of a Yukawa fermion in a thermal bath using finite-temperature cutting rules and effective Green’s functions according to the hard thermal loop resummation technique. We apply this result to the decay of a heavy Majorana neutrino in leptogenesis. Compared to the usual approach where thermal masses are inserted into the kinematics of final states, we find that deviations arise through two different leptonic dispersion relations. The decay rate differs from the usual approach by more than 1 order of magnitude in the temperature range which is interesting for the weak washout regime. We discuss how to arrive at consistent finite-temperature treatments of leptogenesis.

We solve the dispersion relation for the $P$-wave $\pi \pi$ amplitude. We discuss the role of the left-hand cut vs the Castillejo-Dalitz-Dyson pole contribution and compare the solution with a generic quark model description. We review the generic properties of analytical partial wave scattering and production amplitudes and discuss their applicability and fits of experimental data.

In contrast to alternative values, the quantum of area $\Delta A=8\pi l_P^2$ does not follow from the usual statistical interpretation of black hole entropy; on the contrary, a statistical interpretation follows from it. This interpretation is based on the two concepts: nonadditivity of black hole entropy and Landau quantization. Using nonadditivity a microcanonical distribution for a black hole is found and it is shown that the statistical weight of a black hole should be proportional to its area. By analogy with conventional Landau quantization, it is shown that quantization of a black hole is nothing but the Landau quantization. The Landau levels of a black hole and their degeneracy are found. The degree of degeneracy is equal to the number of ways to distribute a patch of area $8\pi l_P^2$ over the horizon. Taking into account these results, it is argued that the black hole entropy should be of the form $S_{\mathrm{bh}}=2\pi ·\Delta \Gamma$, where the number of microstates is $\Delta \Gamma =A/8\pi l_P^2$. The nature of the degrees of freedom responsible for black hole entropy is elucidated. The applications of the new interpretation are presented. The effect of noncommuting coordinates is discussed.

We study the effects of a nonzero magnetic field on a class of $2+1$ dimensional non-Fermi liquids, recently found in [Hong Liu, John McGreevy, and David Vegh, arXiv:0903.2477.] by considering properties of a Fermionic probe in an extremal ${\mathrm{AdS}}^4$ black hole background. Introducing a similar fermionic probe in a dyonic ${\mathrm{AdS}}^4$ black hole geometry, we find that the effect of a magnetic field could be incorporated in a rescaling of the probe fermion’s charge. From this simple fact, we observe interesting effects like gradual disappearance of the Fermi surface and quasiparticle peaks at large magnetic fields and changes in other properties of the system. We also find Landau level like structures and oscillatory phenomena similar to the de-Haas-van Alphen effect.

Cosmological magnetic fields are being observed with ever increasing correlation lengths, possibly reaching the size of superclusters, therefore disfavoring the conventional picture of generation through primordial seeds later amplified by galaxy-bound dynamo mechanisms. In this paper we put forward a fundamentally different approach that links such large-scale magnetic fields to the cosmological vacuum energy. In our scenario the dark energy is due to the Veneziano ghost (which solves the $U(1{)}_A$ problem in QCD). The Veneziano ghost couples through the triangle anomaly to the electromagnetic field with a constant which is unambiguously fixed in the standard model. While this interaction does not produce any physical effects in Minkowski space, it triggers the generation of a magnetic field in an expanding universe at every epoch. The induced energy of the magnetic field is thus proportional to cosmological vacuum energy: ${\rho }_{\mathrm{EM}}\simeq B^2\simeq (\frac{\alpha }{4\pi }{)}^2{\rho }_{\mathrm{DE}}$, ${\rho }_{\mathrm{DE}}$ hence acting as a source for the magnetic energy ${\rho }_{\mathrm{EM}}$. The corresponding numerical estimate leads to a magnitude in the nG range. There are two unique and distinctive predictions of our proposal: an uninterrupted active generation of Hubble size correlated magnetic fields throughout the evolution of the Universe; the presence of parity violation on the enormous scales $1/H$, which apparently has been already observed in CMB. These predictions are entirely rooted into the standard model of particle physics.