We provide a gravity counterpart of the theorem by Hofman and Strominger that in ($1+1$) dimension, chiral scale invariance indicates chiral conformal invariance. We show that the strict null energy condition gives a sufficient condition to guarantee the symmetry enhancement. We also investigate a possibility to construct holographic c-function that decreases along the holographic renormalization group flow.

We provide a simple and straightforward procedure for defining a Virasoro algebra based on the diffeomorphisms near a null surface in a space-time and obtain the entropy density of the null surface from its central charge. We use the off-shell Noether current corresponding to the diffeomorphism invariance of a gravitational Lagrangian $L(g_{ab},R_{abcd})$ and define the Virasoro algebra from its variation. This allows us to identify the central charge and the zero-mode eigenvalue with which we obtain the entropy density of the Killing horizon. Our approach works for all Lanczos-Lovelock models and reproduces the correct Wald entropy. The entire analysis is done off-shell without using the field equations and allows us to define an entropy density for any null surface which acts as a local Rindler horizon for a particular class of observers.

We study the possible dynamical emergence of IR conformal invariance describing the low energy excitations of near-extremal $R$-charged global ${\mathrm{AdS}}_5$ black holes. We find interesting behavior especially when we tune parameters in such a way that the relevant extremal black holes have classically vanishing horizon area, i.e. no classical ground-state entropy, and when we combine the low energy limit with a large $N$ limit of the dual gauge theory. We consider both near-BPS and non-BPS regimes and their near horizon limits, emphasize the differences between the local ${\mathrm{AdS}}_3$ throats emerging in either case, and discuss potential dual IR 2d CFTs for each case. We compare our results with the predictions obtained from the Kerr/CFT correspondence, and obtain a natural quantization for the central charge of the near-BPS emergent IR CFT which we interpret in terms of the open strings stretched between giant gravitons.

In an open Friedmann-Robertson-Walker (FRW) space background, we study the classical and quantum cosmological models in the framework of the recently proposed nonlinear massive gravity theory. Although the constraints which are present in this theory prevent it from admitting the flat and closed FRW models as its cosmological solutions, for the open FRW universe it is not the case. We have shown that, either in the absence of matter or in the presence of a perfect fluid, the classical field equations of such a theory adopt physical solutions for the open FRW model, in which the mass term shows itself as a cosmological constant. These classical solutions consist of two distinguishable branches: One is a contacting universe which tends to a future singularity with zero size, while another is an expanding universe having a past singularity from which it begins its evolution. A classically forbidden region separates these two branches from each other. We then employ the familiar canonical quantization procedure in the given cosmological setting to find the cosmological wave functions. We use the resulting wave function to investigate the possibility of the avoidance of classical singularities due to quantum effects. It is shown that the quantum expectation values of the scale factor, although they have either contracting or expanding phases like their classical counterparts, are not disconnected from each other. Indeed, the classically forbidden region may be replaced by a bouncing period in which the scale factor bounces from the contraction to its expansion eras. Using the Bohmian approach of quantum mechanics, we also compute the Bohmian trajectory and the quantum potential related to the system, which their analysis shows are the direct effects of the mass term on the dynamics of the universe.

We consider universes that are close to Friedmann-Robertson-Walker in the sense that metric perturbations, their time derivatives and first spatial derivatives are small, but second spatial derivatives are not constrained. We show that if we, in addition, assume that the observer four velocity is close to its background value and close to the four-velocity which defines the hypersurface of averaging, the redshift and the average expansion rate remain close to the Friedmann-Robertson-Walker case. However, this is not true for the angular-diameter distance. The four-velocity assumption implies certain conditions on second derivatives of the metric and/or the matter content.

We argue that $\mathcal{N}=4$ supergravity is 3-loop UV-finite because the relevant supersymmetric candidate counterterm is known to be $SL(2,\mathbb{R})\times SO(6)$-invariant, which violates the Noether-Gaillard-Zumino current conservation. Analogous arguments, based on the universality properties of groups of type E7, also apply to $\mathcal{N}=5$, 6, 8 in 4, 5, 7 loops, respectively, since the $1/\mathcal{N}$ supersymmetry invariants, integrals over the fraction of the superspace, break duality symmetry between Bianchi identities and quantum-corrected vector field equations.

We study the hadroproduction of a $CP$-even or $CP$-odd neutral Higgs boson in association with a $Z$ boson in the minimal supersymmetric extension of the standard model. We include the contributions from quark-antiquark annihilation at the tree level and those from gluon-gluon fusion, which proceeds via quark and squark loops, and list compact analytic results. We quantitatively analyze the hadronic cross sections at the CERN Large Hadron Collider assuming a favorable supergravity-inspired scenario of the minimal supersymmetric extension of the standard model.

We investigate the possibility of a fourth sequential generation in the lepton sector. Assuming neutrinos to be Majorana particles and starting from a recent—albeit weak—hint for a nonzero admixture of a fourth generation neutrino from fits to weak lepton and meson decays, we discuss constraints from neutrinoless double beta decay, radiative lepton decay, and like-sign dilepton production at hadron colliders. Also, an idea for fourth generation neutrino mass model building is briefly outlined. Here we soften the large hierarchy of the neutrino masses within an extradimensional model that locates each generation on different lepton number violating branes without large hierarchies.

We show that production of the Higgs boson through gluon-fusion may be suppressed in the presence of colored scalars. Substantial destructive interference between the top-quark diagrams and colored scalar diagrams is possible due to cancellations between the real (and also imaginary) parts of the amplitudes. As an example, we consider a color-octet scalar that has a negative, order-one coupling to the Higgs doublet. We find that gluon fusion can be suppressed by more than an order of magnitude when the scalar mass is below a few hundred GeV, while milder suppressions occur for larger scalar masses or smaller couplings. Thus, the standard model extended with only one particle can evade the full range of present LHC exclusion limits on the Higgs mass. The colored scalars, however, would be produced in pairs with a large rate at the LHC, leading to multijet final states to which the LHC experiments are now becoming sensitive.

The LHC has started to explore the TeV energy regime, probing the standard model beyond the LEP and Tevatron. We show how the dijet measurements at the LHC are able to test certain sectors of the standard model at an unprecedented level. We provide the best bounds on all possible four-quark interactions and translate them into limits on the compositeness scale of the quarks and gluons. We also provide constraints on extra gauge bosons, $Z^{\prime }$, $W^{\prime }$, and $G^{\prime }$, and on new interactions proposed to explain the present measurement of the forward-backward asymmetry of the top.

We present branching fraction measurements for the decays $B^0\to {\rho }^0{K}^{*0}$, $B^0\to f_0{K}^{*0}$, and $B^0\to {\rho }^{-}{K}^{*+}$, where $K^{*}$ is an $S$-wave $(K\pi {)}_0^{*}$ or a $K^{*}(892)$ meson; we also measure $B^0\to f_0{K}_2^{*}(1430{)}^0$. For the $K^{*}(892)$ channels, we report measurements of longitudinal polarization fractions (for $\rho$ final states) and direct $CP$ violation asymmetries. These results are obtained from a sample of $(471.0\pm 2.8)\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider at the SLAC National Accelerator Laboratory. We observe ${\rho }^0{K}^{*}(892{)}^0$, ${\rho }^0(K\pi {)}_0^{*0}$, $f_0{K}^{*}(892{)}^0$, and ${\rho }^{-}{K}^{*}(892{)}^{+}$ with greater than $5\sigma$ significance, including systematics. We report first evidence for $f_0(K\pi {)}_0^{*0}$ and $f_0{K}_2^{*}(1430{)}^0$, and place an upper limit on ${\rho }^{-}(K\pi {)}_0^{*+}$. Our results in the $K^{*}(892)$ channels are consistent with no direct $CP$ violation.

The ATLAS detector is used to search for excited leptons in the electromagnetic radiative decay channel ${\ell }^{*}\to \ell \gamma$. Results are presented based on the analysis of $pp$ collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of $2.05\mathrm{f}{\mathrm{b}}^{-1}$. No evidence for excited leptons is found, and limits are set on the compositeness scale $\Lambda$ as a function of the excited lepton mass $m_{{\ell }^{*}}$. In the special case where $\Lambda =m_{{\ell }^{*}}$, excited electron and muon masses below 1.87 TeV and 1.75 TeV are excluded at 95% C.L., respectively.

We report the combination of recent measurements of the helicity of the $W$ boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of $2.7–5.4\mathrm{f}{\mathrm{b}}^{-1}$ of $p\overline{p}$ collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of $W$ bosons with longitudinal ($f_0$) and right-handed ($f_{+}$) helicities, we find $f_0=0.722\pm 0.081[\pm 0.062(\mathrm{stat})\pm 0.052(\mathrm{syst})]$ and $f_{+}=-0.033\pm 0.046[\pm 0.034(\mathrm{stat})\pm 0.031(\mathrm{syst})]$. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find $f_0=0.682\pm 0.057[\pm 0.035(\mathrm{stat})\pm 0.046(\mathrm{syst})]$ for fixed $f_{+}$ and $f_{+}=-0.015\pm 0.035[\pm 0.018(\mathrm{stat})\pm 0.030(\mathrm{syst})]$ for fixed $f_0$. The results are consistent with standard model expectations.

We calculate the Chern-Simons diffusion rate in a strongly coupled $\mathcal{N}=4$ super Yang-Mills plasma in the presence of a constant external $U(1{)}_R$ magnetic flux via the holographic correspondence. Because of the strong interactions between the charged fields and non-Abelian gauge fields, the external Abelian magnetic field affects the thermal Yang-Mills dynamics and increases the diffusion rate, regardless of its strength. We obtain the analytic results for the Chern-Simons diffusion rate both in the weak and strong magnetic field limits. In the latter limit, we show that the diffusion rate scales as $B\times T^2$ and this can be understood as a result of a dynamical dimensional reduction.

The rise time of a Galactic supernova (SN) ${\overline{\nu }}_e$ light curve, observable at a high-statistics experiment such as the Icecube Cherenkov detector, can provide a diagnostic tool for the neutrino mass hierarchy at “large” 1–3 leptonic mixing angle ${\vartheta }_{13}$. Thanks to the combination of matter suppression of collective effects at early post-bounce times on one hand and the presence of the ordinary Mikheyev-Smirnov-Wolfenstein effect in the outer layers of the SN on the other hand, a sufficiently fast rise time on $\mathcal{O}(100)\mathrm{ms}$ scale is indicative of an inverted mass hierarchy. We investigate results from an extensive set of stellar core-collapse simulations, providing a first exploration of the astrophysical robustness of these features. We find that for all the models analyzed (sharing the same weak interaction microphysics) the rise times for the same hierarchy are similar not only qualitatively, but also quantitatively, with the signals for the two classes of hierarchies significantly separated. We show via Monte Carlo simulations that the two cases should be distinguishable at IceCube for SNe at a typical Galactic distance 99% of the time. Finally, a preliminary survey seems to show that the faster rise time for inverted hierarchy as compared to normal hierarchy is a qualitatively robust feature predicted by several simulation groups. Since the viability of this signature ultimately depends on the quantitative assessment of theoretical/numerical uncertainties, our results motivate an extensive campaign of comparison of different code predictions at early accretion times with implementation of microphysics of comparable sophistication, including effects such as nucleon recoils in weak interactions.

We present a solution of the coupled Einstein and rank-two antisymmetric tensor field equations where Lorentz symmetry is spontaneously broken, and we discuss its observational signatures. Especially, the deflection angles have important qualitative differences between tensor and scalar monopoles. If a monopole were to be detected, it would be discriminated whether or not to correspond to a tensor one. This phenomenon might open up new directions in the search of Lorentz violation with future astrophysical observations.

We consider the low-energy effective field theory describing the infrared dynamics of nondissipative fluids. We extend previous work to accommodate conserved charges, and we clarify the matching between field-theory variables and thermodynamical ones. We discuss the systematics of the derivative expansion, for which field theory offers a conceptually clear and technically neat scheme. As an example, we compute the correction to the sound-wave dispersion relation coming from a sample second-order term. This formalism forms the basis for a study of anomalies in hydrodynamics via effective field theory, which is initiated in a companion paper.

Motivated by the gauge/gravity duality, we introduce a numerical scheme based on generalized harmonic evolution to solve the Einstein field equations on asymptotically anti-de Sitter spacetimes. We work in global ${\mathrm{AdS}}_5$, which can be described by the ($t$, $r$, $\chi$, $\theta$, $\varphi$) spherical coordinates adapted to the $\mathbb{R}\times S^3$ boundary. We focus on solutions that preserve an $SO(3)$ symmetry that acts to rotate the 2-spheres parametrized by $\theta$, $\varphi$. In the boundary conformal field theory, the way in which this symmetry manifests itself hinges on the way we choose to embed Minkowski space in $\mathbb{R}\times S^3$. We present results from an ongoing study of prompt black hole formation via scalar field collapse, and explore the subsequent quasinormal ringdown. Beginning with initial data characterized by highly distorted apparent horizon geometries, the metrics quickly evolve, via quasinormal ringdown, to equilibrium static black hole solutions at late times. The lowest angular number quasinormal modes are consistent with the linear modes previously found in perturbative studies, whereas the higher angular modes are a combination of linear modes and of harmonics arising from nonlinear mode coupling. We extract the stress energy tensor of the dual conformal field theory on the boundary, and find that despite being highly inhomogeneous initially, it nevertheless evolves from the outset in a manner that is consistent with a thermalized $\mathcal{N}=4\mathrm{SYM}$ fluid. As a first step towards closer contact with relativistic heavy ion collision physics, we map this solution to a Minkowski piece of the $\mathbb{R}\times S^3$ boundary, and obtain a corresponding fluid flow in Minkowski space.

Tensor models generalize random matrix models in yielding a theory of dynamical triangulations in arbitrary dimensions. Colored tensor models have been shown to admit a $1/N$ expansion and a continuum limit accessible analytically. In this paper we prove that these results extend to the most general tensor model for a single generic, i.e. nonsymmetric, complex tensor. Colors appear in this setting as a canonical bookkeeping device and not as a fundamental feature. In the large $N$ limit, we exhibit a set of Virasoro constraints satisfied by the free energy and an infinite family of multicritical behaviors with entropy exponents ${\gamma }_m=1-1/m$.