We construct some examples of $D=3$, $\mathcal{N}=4$ GW theory and $\mathcal{N}=5$ superconformal Chern-Simons matter theory by using the covariantly constant curvature of a quaternionic-Kahler manifold to construct the symplectic 3-algebra in the theories. Comparing with the previous theories, the $\mathcal{N}=4$, 5 theories constructed in this way possess a local $Sp(2n)$ symmetry and a diffeomorphism symmetry associated with the quaternionic-Kahler manifold. We also construct a generalized $\mathcal{N}=8$ BLG theory by utilizing the dual curvature operator of a maximally symmetric space of dimension 4 to construct the Nambu 3-algebra. Comparing with the previous $\mathcal{N}=8$ BLG theory, the theory has a diffeomorphism invariance and a local $SO(4)$ invariance associated with the symmetric space.

We discuss a fine-tuning of rather generic 3-dimensional higher-curvature gravity actions that leads to gauge symmetry enhancement at the linearized level via partial masslessness. Requiring this gauge symmetry to be present also nonlinearly reduces such actions to conformal Chern–Simons gravity. We perform a canonical analysis of this theory and construct the gauge generators and associated charges. We provide and classify admissible boundary conditions. The boundary conditions on the conformal equivalence class of the metric render one chirality of the partially massless Weyl gravitons normalizable and the remaining one non-normalizable. There are three choices—trivial, fixed, or free—for the Weyl factors of the bulk metric and of the boundary metric. This proliferation of boundary conditions leads to various physically distinct scenarios of holography that we study in detail, extending considerably the discussion initiated in Ref. [1]. In particular, the dual CFT may contain an additional scalar field with or without background charge, depending on the choices above.

In this paper we introduce a simple discrete stochastic model of eternal inflation that shares many of the most important features of the continuum theory as it is now understood. The model allows us to construct a multiverse and rigorously analyze its properties. Although simple and easy to solve, it has a rich mathematical structure underlying it. Despite the discreteness of the space-time the theory exhibits an unexpected nonperturbative analog of conformal symmetry that acts on the boundary of the geometry. The symmetry is rooted in the mathematical properties of trees, $p$-adic numbers, and ultrametric spaces; and in the physical property of detailed balance. We provide self-contained elementary explanations of the unfamiliar mathematical concepts, which have also appeared in the study of the $p$-adic string. The symmetry acts on a huge collection of very low-dimensional “multiverse fields” that are not associated with the usual perturbative degrees of freedom. They are connected with the late-time statistical distribution of bubble-universes in the multiverse. The conformal symmetry which acts on the multiverse fields is broken by the existence of terminal decays—to hats or crunches—but in a particularly simple way. We interpret this symmetry breaking as giving rise to an arrow of time. The model is used to calculate statistical correlations at late time and to discuss the measure problem. We show that the natural cutoff in the model is the analog of the so-called light-cone-time cutoff. Applying the model to the problem of the cosmological constant, we find agreement with earlier work.

Coherent state functional integrals for the minisuperspace models of quantum cosmology are studied. By the well-established canonical theories, the transition amplitudes in the path-integral representations of Wheeler-DeWitt quantum cosmology and loop quantum cosmology can be formulated through group averaging. The effective action and Hamiltonian with higher-order quantum corrections are thus obtained in both models within the scheme of Gaussian coherent states. It turns out that for a nonsymmetric Hamiltonian constraint operator, the Moyal *-product emerges naturally in the effective Hamiltonian. This reveals the intrinsic relation among coherent state functional integral, effective theory, and Moyal *-product. Moreover, both the resulted effective theories imply a possible quantum cosmological effect in large scale limit under certain condition.

We extract $\eta$-${\eta }^{\prime }$ mixing angle and the ratios of decay constants of light pseudoscalar mesons ${\pi }^0$, $\eta$, and ${\eta }^{\prime }$ using recently available BABAR measurements on $\eta$-photon and ${\eta }^{\prime }$-photon transition form factors and more accurate experimental data for the masses and two-photon decay widths of the light pseduoscalar mesons.

For top quarks produced via the subprocess $q\overline{q}\to t\overline{t}$, the longitudinal $t$-quark polarization ($P_{\parallel }$) vanishes in QCD. $P_{\parallel }$ can be measured by the angular distribution of the lepton in $t$-quark semileptonic decay. New physics contributions that are parity nonconserving will be manifest by nonvanishing $P_{\parallel }$, which may be large. We illustrate this with the $s$-channel exchange of a massive $X$ gluon with chiral quark couplings.

Several extensions of the standard model predict the existence of new neutral spin-1 resonances associated with the electroweak symmetry breaking sector. Using the data from ATLAS (with integrated luminosity of $\mathcal{L}=1.02{\mathrm{fb}}^{-1}$) and CMS (with integrated luminosity of $\mathcal{L}=1.55{\mathrm{fb}}^{-1}$) on the production of $W^{+}{W}^{-}$ pairs through the process $pp\to {\ell }^{+}{\ell }^{\prime -}{\mathrm{E̸}}_T$, we place model independent bounds on these new vector resonances masses, couplings, and widths. Our analyses show that the present data exclude new neutral vector resonances with masses up to 1–2.3 TeV depending on their couplings and widths. We also demonstrate how to extend our analysis framework to different models with a specific example.

We interpret the recent data on nonobservation of $Z^{\prime }$ and $W^{\prime }$ bosons, reported by CMS, within minimal walking technicolor models and use them to constrain the couplings and spectrum of the theory. We provide the reach for both exclusion and possible observation for the LHC with $5{\mathrm{fb}}^{-1}$ at 7 TeV in the center of mass energy, and $100{\mathrm{fb}}^{-1}$ at 13 TeV.

The diffractive heavy quark cross sections are estimated considering photon-Pomeron ($\gamma \mathbb{P}$) interactions in hadron-hadron colliders at RHIC, Tevatron, and CERN LHC energies. We assume the validity of the hard diffractive factorization and calculate the charm and bottom total cross sections and rapidity distributions using the diffractive parton distribution functions of the Pomeron obtained by the H1 Collaboration at DESY-HERA. Moreover, we compare our predictions with those obtained using the dipole model. We verify that this process is a good test of the different mechanisms for diffractive heavy quark production at hadron-hadron colliders.

A new Super-Kamiokande search for supernova relic neutrinos was conducted using 2853 live days of data. Sensitivity is now greatly improved compared to the 2003 Super-Kamiokande result, which placed a flux limit near many theoretical predictions. This more detailed analysis includes a variety of improvements such as increased efficiency, a lower energy threshold, and an expanded data set. New combined upper limits on supernova relic neutrino flux are between 2.8 and $3.1{\overline{\nu }}_e{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}>16\mathrm{MeV}$ total positron energy (17.3 MeV ${\mathrm{E}}_{\nu }$).

Motivated by gauge theory/string theory correspondence, a lower bound on the bulk viscosity of strongly coupled gauge theory plasma was proposed in [A. Buchel, Phys. Lett. B 663, 286 (2008).]. We consider strongly coupled $\mathcal{N}=4$ supersymmetric Yang-Mills plasma compactified on a two-manifold of constant curvature $\beta$. We show that the effective $(1+1)$-dimensional hydrodynamic description of the system is governed by the bulk viscosity violating the bound of [A. Buchel, Phys. Lett. B 663, 286 (2008).], once $\beta <0$.

The extension of the minimal standard model by three right-handed sterile neutrinos with masses smaller than the electroweak scale ($\nu \mathrm{MSM}$) is discussed in a $Q_6$ flavor symmetry framework. The lightness of the keV sterile neutrino and the near mass degeneracy of two heavier sterile neutrinos are naturally explained by exploiting group properties of $Q_6$. A normal hierarchical mass spectrum and an approximately $\mu \mathrm{\text{−}}\tau$ symmetric mass matrix are predicted for three active neutrinos. Nonzero ${\theta }_{13}$ can be obtained together with a deviation of ${\theta }_{23}$ from the maximality, where both mixing angles are consistent with the latest global data including T2K and MINOS results. Furthermore, the tiny active-sterile mixing is related to the mass ratio between the lightest active and lightest sterile neutrinos.

In this work we consider fermionic zero modes in the external scalar and electromagnetic field forming the vortex on a sphere. We find the correspondence between the equations for the fermions in different dimensions, find their explicit expressions through the vortex fields in the case of massless fermions, asymptotics near the poles in the case of massive fermions, and check the number of the solutions by proving the index theorem for the fermions on a sphere. As a part of deriving the index, we write a detailed calculation of the Green function of the Heat equation.

We study the theory of a (global) texture with DBI-like Lagrangian, the higher-dimensional generalization of the previously known chiral Born-Infeld theory. This model evades Derrick’s theorem and enables the existence of solitonic solutions in arbitrary ($N+1$) dimensions. We explicitly show the solutions in spherically symmetric ansatz. These are examples of extended topological solitons. We then investigate the coupling of this theory to gravity, and obtain the static self-gravitating solitonic $p$-brane solutions. These nonsingular branes can be identified as the smooth versions of cosmic $p$-branes which, in the thin-wall limit, suffers from naked singularities.

The cross section of elastic electron-proton scattering taking place in an electron gas is calculated within the closed time path method by means of the resummation of the one-loop self-energy in the photon propagator. Backreaction of the colliding particles on the gas has been taken into account and is found to be dominating the cross section when the energy exchange falls in the vicinity of the Fermi energy. Backreaction reflects the colliding particles-gas entanglement and makes the colliding particle state mixed. The softness of the asymptotic particle-hole states of the gas makes the colliding particle trajectories more consistent and the collision irreversible, rendering in this manner the scattering more classical in this regime.

We study massless scalar and electromagnetic fields from static sources in a static higher-dimensional spacetime. Exact expressions for static Green’s functions for such problems are obtained in the background of the Majumdar-Papapetrou solutions of the Einstein-Maxwell equations. Using this result, we calculate the force between two scalar or electric charges in the presence of one or several extremally charged black holes in equilibrium in the higher-dimensional spacetime.

We consider two specific approaches to evaluate the black hole entropy which are known to produce correct results in the case of Einstein’s theory and generalize them to Lanczos-Lovelock models. In the first approach (which could be called extrinsic), we use a procedure motivated by earlier work by Pretorius, Vollick, and Israel, and by Oppenheim, and evaluate the entropy of a configuration of densely packed gravitating shells on the verge of forming a black hole in Lanczos-Lovelock theories of gravity. We find that this matter entropy is not equal to (it is less than) Wald entropy, except in the case of Einstein theory, where they are equal. The matter entropy is proportional to the Wald entropy if we consider a specific $m$th-order Lanczos-Lovelock model, with the proportionality constant depending on the spacetime dimensions $D$ and the order $m$ of the Lanczos-Lovelock theory as $(D-2m)/(D-2)$. Since the proportionality constant depends on $m$, the proportionality between matter entropy and Wald entropy breaks down when we consider a sum of Lanczos-Lovelock actions involving different $m$. In the second approach (which could be called intrinsic), we generalize a procedure, previously introduced by Padmanabhan in the context of general relativity, to study off-shell entropy of a class of metrics with horizon using a path integral method. We consider the Euclidean action of Lanczos-Lovelock models for a class of metrics off shell and interpret it as a partition function. We show that in the case of spherically symmetric metrics, one can interpret the Euclidean action as the free energy and read off both the entropy and energy of a black hole spacetime. Surprisingly enough, this leads to exactly the Wald entropy and the energy of the spacetime in Lanczos-Lovelock models obtained by other methods. We comment on possible implications of the result.

We investigate nonlinear $f(R)$ theories in the Kaluza-Klein models with toroidal compactification of extra dimensions. A pointlike matter source has the dustlike equation of state in our three dimensions and nonzero equations of state in the extra dimensions. We obtain solutions of linearized Einstein equations with this matter source taking into account effects of nonlinearity of the model. There are two asymptotic regions where solutions satisfy the gravitational tests at the same level of accuracy as general relativity. According to these asymptotic regions, there are two classes of solutions. We call these solutions asymptotic latent solitons. The asymptotic latent solitons from the first class generalize the known result of the linear theory. The asymptotic black strings and black branes are particular cases of these asymptotic solutions. The second class of asymptotic solitons exists only in multidimensional nonlinear models. The main feature for both of these classes of solutions is that the matter sources have tension in the extra dimensions.

As a neutron star (NS) is tidally disrupted by a black hole (BH) companion at the end of a black-hole–neutron-star (BHNS) binary inspiral, its magnetic fields will be stretched and amplified. If sufficiently strong, these magnetic fields may impact the gravitational waveforms, merger evolution and mass of the remnant disk. Formation of highly-collimated magnetic field lines in the $\mathrm{\text{disk}}+\mathrm{\text{spinning}}$ BH remnant may launch relativistic jets, providing the engine for a short-hard GRB. We analyze this scenario through fully general relativistic, magnetohydrodynamic BHNS simulations from inspiral through merger and disk formation. Different initial magnetic field configurations and strengths are chosen for the NS interior for both nonspinning and moderately spinning ($a_{\mathrm{BH}}/M_{\mathrm{BH}}=0.75$) BHs aligned with the orbital angular momentum. Only strong interior ($B_{\max }\sim {10}^{17}\mathrm{G}$) initial magnetic fields in the NS significantly influence merger dynamics, enhancing the remnant disk mass by 100% and 40% in the nonspinning and spinning BH cases, respectively. However, detecting the imprint of even a strong magnetic field may be challenging for Advanced LIGO. Though there is no evidence of mass outflows or magnetic field collimation during the preliminary simulations we have performed, higher resolution, coupled with longer disk evolutions and different initial magnetic field configurations, may be required to definitively assess the possibility of BHNS binaries as short-hard gamma-ray burst progenitors.

We investigate the classical gravitational tests for the six-dimensional Kaluza-Klein model with spherical (of a radius $a$) compactification of the internal space. The model contains also a bare multidimensional cosmological constant ${\Lambda }_6$. The matter, which corresponds to this ansatz, can be simulated by a perfect fluid with the vacuum equation of state in the external space and an arbitrary equation of state with the parameter ${\omega }_1$ in the internal space. For example, ${\omega }_1=1$ and ${\omega }_1=2$ correspond to the monopole two-forms and the Casimir effect, respectively. In the particular case ${\Lambda }_6=0$, the parameter ${\omega }_1$ is also absent: ${\omega }_1=0$. In the weak-field approximation, we perturb the background ansatz by a pointlike mass. We demonstrate that in the case ${\omega }_1>0$ the perturbed metric coefficients have the Yukawa-type corrections with respect to the usual Newtonian gravitational potential. The inverse square law experiments restrict the parameters of the model: $a/\sqrt{{\omega }_1}\lesssim 6\times {10}^{-3}\mathrm{cm}$. Therefore, in the Solar System the parameterized post-Newtonian parameter $\gamma$ is equal to 1 with very high accuracy. Thus, our model satisfies the gravitational experiments (the deflection of light and the time delay of radar echoes) at the same level of accuracy as general relativity. We demonstrate also that our background matter provides the stable compactification of the internal space in the case ${\omega }_1>0$. However, if ${\omega }_1=0$, then the parameterized post-Newtonian parameter $\gamma =1/3$, which strongly contradicts the observations.