We identify a particularly simple class of supergravity models describing superconformal coupling of matter to supergravity. In these models, which we call the canonical superconformal supergravity models, the kinetic terms in the Jordan frame are canonical, and the scalar potential is the same as in the global theory. The pure supergravity part of the total action has a local Poincaré supersymmetry, whereas the chiral and vector multiplets coupled to supergravity have a larger local superconformal symmetry. The scale-free globally supersymmetric theories, such as the NMSSM with a scale-invariant superpotential, can be naturally embedded into this class of theories. After the supergravity embedding, the Jordan frame scalar potential of such theories remains scale free; it is quartic, it contains no mass terms, no nonrenormalizable terms, no cosmological constant. The local superconformal symmetry can be broken by additional terms, which, in the small field limit, are suppressed by the gravitational coupling. This can be achieved by introducing the nonminimal scalar-curvature coupling, and by taking into account interactions with a hidden sector. In this approach, the smallness of the mass parameters in the NMSSM may be traced back to the original superconformal invariance. This allows one to address the $\mu$ problem and the cosmological domain wall problem in this model, and to implement chaotic inflation in the NMSSM. We discuss the gravitino problem in the NMSSM inflation, as well as the possibility to obtain a broad class of new versions of chaotic inflation in supergravity.

Lorentz-invariant scalar-field theories in $d+1$ dimensions with second-order derivative terms are unable to support static soliton solutions that are both finite in energy and stable for $d>2$, a result known as Derrick’s theorem. Lifshitz theories, which introduce higher-order spatial derivatives, need not obey Derrick’s theorem. We construct stable, finite-energy, static soliton solutions in Lifshitz scalar-field theories in $3+1$ dimensions with a dynamical critical exponent $z=2$. We exhibit three generic types: nontopological point defects, topological point defects, and topological strings. We focus mainly on Lifshitz theories that are defined through a superpotential and admit Bogomolnyi-Prasad-Sommerfield solutions. These kinds of theories are the bosonic sectors of supersymmetric theories derived from the stochastic dynamics of a scalar field theory in one higher dimension. If nature obeys a Lifshitz field theory in the ultraviolet, then the novel topological defects discussed here may exist as relics from the early universe. Their discovery would prove that standard field theory breaks down at short distance scales.

We pursue the construction of higher-spin theory in ${\mathrm{AdS}}_4$ from ${\mathrm{CFT}}_3$ of the O(N) vector model in terms of canonical collective fields. In null-plane quantization an exact map is established between the two spaces. The coordinates of the ${\mathrm{AdS}}_4$ space-time are generated from the collective coordinates of the bi-local field. This, in the light-cone gauge, provides an exact one-to-one reconstruction of bulk ${\mathrm{AdS}}_4$ space-time and higher-spin fields.

The zeta function regularization technique is used to study the finite temperature Casimir effect for a massless Majorana fermion field confined between parallel plates and satisfying bag boundary conditions. A magnetic field perpendicular to the plates is included. An expression for the zeta function is obtained, which is exact to all orders in the magnetic field strength, temperature and plate distance. The zeta function is used to calculate the Helmholtz free energy of the Majorana field and the pressure on the plates, in the case of weak magnetic field and strong magnetic field. In both cases, simple analytic expressions are obtained for the free energy and pressure which are very accurate and valid for all values of the temperature and plate distance.

We consider the quantum dynamics of a harmonic oscillator in noncommutative space under the influence of linearized gravitational waves (GWs) in the long-wavelength and low-velocity limit. Following the prescription in Saha and Gangopadhyay [Phys. Lett. B 681, 96 (2009)] we quantize the system. The Hamiltonian of the system is solved by using standard algebraic iterative methods. The solution shows signatures of the coordinate noncommutativity via alterations in the oscillation frequency of the harmonic oscillator system from its commutative counterpart. Moreover, it is found that the response of the harmonic oscillator to periodic GWs, when their frequencies match, will oscillate with a time scale imposed by the noncommutative parameter. We expect this noncommutative signature to show up as some noise source in the GW detection experiments since the recent phenomenological upper bounds set on the spatial noncommutative parameter imply a length scale comparable to the length variations due to the passage of gravitational waves, detectable in the present-day GW detectors.

Motivated by possible applications within the framework of anti-de Sitter gravity/conformal field theory correspondence, charged black holes with AdS asymptotics, which are solutions to Einstein-Gauss-Bonnet gravity in $D$ dimensions, and whose electric field is described by nonlinear electrodynamics are studied. For a topological static black hole ansatz, the field equations are exactly solved in terms of the electromagnetic stress tensor for an arbitrary nonlinear electrodynamic Lagrangian in any dimension $D$ and for arbitrary positive values of Gauss-Bonnet coupling. In particular, this procedure reproduces the black hole metric in Born-Infeld and conformally invariant electrodynamics previously found in the literature. Altogether, it extends to $D>4$ the four-dimensional solution obtained by Soleng in logarithmic electrodynamics, which comes from vacuum polarization effects. Falloff conditions for the electromagnetic field that ensure the finiteness of the electric charge are also discussed. The black hole mass and vacuum energy as conserved quantities associated to an asymptotic timelike Killing vector are computed using a background-independent regularization of the gravitational action based on the addition of counterterms which are a given polynomial in the intrinsic and extrinsic curvatures.

Astrophysically realistic black holes may have spins that are nearly extremal (i.e., close to 1 in dimensionless units). Numerical simulations of binary black holes are important tools both for calibrating analytical templates for gravitational-wave detection and for exploring the nonlinear dynamics of curved spacetime. However, all previous simulations of binary-black-hole inspiral, merger, and ringdown have been limited by an apparently insurmountable barrier: the merging holes’ spins could not exceed 0.93, which is still a long way from the maximum possible value in terms of the physical effects of the spin. In this paper, we surpass this limit for the first time, opening the way to explore numerically the behavior of merging, nearly extremal black holes. Specifically, using an improved initial-data method suitable for binary black holes with nearly extremal spins, we simulate the inspiral (through 12.5 orbits), merger and ringdown of two equal-mass black holes with equal spins of magnitude 0.95 antialigned with the orbital angular momentum.

We consider here the classic scenario given by Oppenheimer, Snyder, and Datt, for the gravitational collapse of a massive matter cloud, and examine its stability under the introduction of small tangential stresses. We show, by offering an explicit class of physically valid tangential stress perturbations, that an introduction of tangential pressure, however small, can qualitatively change the final fate of collapse from a black hole final state to a naked singularity. This shows instability of black hole formation in collapse and sheds important light on the nature of cosmic censorship hypothesis and its possible formulations. The key effect of these perturbations is to alter the trapped surface formation pattern within the collapsing cloud and the apparent horizon structure. This allows the singularity to be visible, and implications are discussed.

We investigate the cosmological perturbations in $f(T)$ gravity. Examining the pure gravitational perturbations in the scalar sector using a diagonal vierbein, we extract the corresponding dispersion relation, which provides a constraint on the $f(T)$ Ansätze that lead to a theory free of instabilities. Additionally, upon inclusion of the matter perturbations, we derive the fully perturbed equations of motion, and we study the growth of matter overdensities. We show that $f(T)$ gravity with $f(T)$ constant coincides with General Relativity, both at the background as well as at the first-order perturbation level. Applying our formalism to the power-law model we find that on large subhorizon scales ($\mathcal{O}(100\mathrm{Mpc})$ or larger), the evolution of matter overdensity will differ from $\Lambda \mathrm{CDM}$ cosmology. Finally, examining the linear perturbations of the vector and tensor sectors, we find that (for the standard choice of vierbein) $f(T)$ gravity is free of massive gravitons.

Local non-Gaussianity causes correlations between large-scale perturbation modes and the small-scale power. The large-scale CMB signal has contributions from the integrated Sachs-Wolfe (ISW) effect, which does not correlate with the small-scale power. If this ISW contribution can be removed, the sensitivity to local non-Gaussianity is improved. Gravitational lensing and galaxy counts can be used to trace the ISW contribution; in particular, we show that the CMB lensing potential is highly correlated with the ISW signal. We construct a nearly optimal estimator for the local non-Gaussianity parameter $f_{\mathrm{NL}}$ and investigate to what extent we can use this to decrease the variance on $f_{\mathrm{NL}}$. We show that the variance can be decreased by up to 20% at Planck sensitivity using galaxy counts. CMB lensing is a good bias-independent ISW tracer for future more sensitive observations, though the fractional decrease in variance is small if good polarization data are also available.

A solution to the PAMELA positron excess with Higgsino dark matter within extended supergravity grand unified (SUGRA) models is proposed. The models are compliant with the photon constraints recently set by Fermi-LAT and produce positron as well as antiproton fluxes consistent with the PAMELA experiment. The SUGRA models considered have an extended hidden sector with extra degrees of freedom which allow for a satisfaction of relic density consistent with WMAP. The Higgsino models are also consistent with the CDMS-II and XENON100 data and are discoverable at LHC-7 with $1{\mathrm{fb}}^{-1}$ of luminosity. The models are testable on several fronts.

The escape fraction at infinity is evaluated for massless particles produced in collisions of weakly interacting particles accreted into a density spike near the particle horizon of an extremal Kerr black hole, for the case of equatorial orbits. We compare with the Schwarzschild case, and argue that in the case of extremal black holes, redshifted signatures can be produced that could potentially explore the physics of particle collisions at center of mass energies that extend beyond those of any feasible terrestrial accelerator.

In almost all of plasma theories for astrophysical objects, we have assumed the charge quasineutrality of unmagnetized plasmas in global scales. This assumption has been justified because if there is a charged plasma, it induces the electric field which attracts the opposite charge, and this opposite charge reduces the charge separation. Here, we report a newly discovered instability which causes a charge separation in a rotating plasma inside of an innermost stable circular orbit (ISCO) around a black hole. The growth rate of the instability is smaller than that of the disk instability even in the unstable disk region and is forbidden in the stable disk region outside of the ISCO. However, this growth rate becomes comparable to that of the disk instability when the plasma density is much lower than a critical density inside of the ISCO. In such case, the charge separation instability would become apparent and cause the charged accretion into the black hole, thus charge the hole.

Forward-backward asymmetry $A_{\mathrm{FB}}$ is an essential observable to study the nature of coupling in the standard model and physics beyond the standard model, as shown at LEP and Tevatron. As a proton-proton collider, the LHC does not have the preferred direction contrary to her counterparts, namely, LEP and Tevatron. Therefore, $A_{\mathrm{FB}}$ is not applicable at the LHC. However, for the proton the momentum of the valence quark is usually larger than that of the sea quark. Utilizing this feature we have defined a so-called one-side forward-backward asymmetry $A_{\mathrm{OFB}}$ for the top quark pair production at the LHC in the previous work. In this paper we extend our studies to the charged leptons and bottom quarks as the final states. Our numerical results show that at the LHC $A_{\mathrm{OFB}}$ can be utilized to study the nature of the couplings once enough events are collected.

We determine the chiral phase transition line in $(2+1)$-flavor QCD for small values of the light quark chemical potential. We show that for small values of the chemical potential the curvature of the phase transition line can be deduced from an analysis of scaling properties of the chiral condensate and its susceptibilities. To do so we extend earlier studies of the magnetic equation of state in $(2+1)$-flavor QCD to finer lattice spacings, $aT=1/8$. We use these universal scaling properties of the chiral order parameter to extract the curvature of the transition line at two values of the cutoff, $aT=1/4$ and $1/8$. We find that cutoff effects are small for the curvature parameter and determine the transition line in the chiral limit to leading order in the light quark chemical potential. We obtain $T_c({\mu }_q)/T_c(0)=1-0.059(2)(4)({\mu }_q/T{)}^2+\mathcal{O}({\mu }_q^4)$.

In this paper we develop a formalism to evaluate wave functions in momentum and coordinate space for the resonant states dynamically generated in a unitary coupled channel approach. The on-shell approach for the scattering matrix, commonly used, is also obtained in quantum mechanics with a separable potential, which allows one to write wave functions in a trivial way. We develop useful relationships among the couplings of the dynamically generated resonances to the different channels and the wave functions at the origin. The formalism provides an intuitive picture of the resonances in the coupled channel approach, as bound states of one bound channel, which decays into open ones. It also provides an insight and practical rules for evaluating couplings of the resonances to external sources and how to deal with final state interaction in production processes. As an application of the formalism we evaluate the wave functions of the two $\Lambda (1405)$ states in the $\pi \Sigma$, $\overline{K}N$, and other coupled channels. It also offers a practical way to study three-body systems when two of them cluster into a resonance.

In the framework of QCD factorization, based on the first order of isospin violation, we study direct $CP$ violation in the decay of ${\overline{B}}_s^0\to K^0{\rho }^0(\omega )\to K^0{\pi }^{+}{\pi }^{-}$, including the effect of $\rho -\omega$ mixing. We find that the $CP$ violating asymmetry is large via the $\rho -\omega$ mixing mechanism when the invariant mass of the ${\pi }^{+}{\pi }^{-}$ pair is in the vicinity of the $\omega$ resonance. For the decay of ${\overline{B}}_s^0\to K^0{\rho }^0(\omega )\to K^0{\pi }^{+}{\pi }^{-}$, the maximum $CP$ violating asymmetries can reach about 46%. We also discuss the possibility to observe the predicted $CP$ violating asymmetries at the LHC.

 We study steady-state spherically symmetric accretion of a Galileon field onto a Schwarzschild black hole in the test-fluid approximation. The Galileon is assumed to undergo a stage of cosmological evolution, thus setting a nontrivial boundary condition at spatial infinity. The critical flow is found for some parameters of the theory. There is a range of parameters when the critical flow exists, but the solution is unstable. It is also shown that for a certain range of parameters the critical flow solution does not exist. Depending on the model the sound horizon of the flow can be either outside or inside of the Schwarzschild horizon. The latter property may make it problematic to embed the Galileon theory in the standard black hole thermodynamics.

We describe in detail the general methodology and numerical implementation of consistent $N$-body simulations for coupled-scalar-field models, including background cosmology and the generation of initial conditions (with the different couplings to different matter species taken into account). We perform fully consistent simulations for a class of coupled-scalar-field models with an inverse power-law potential and negative coupling constant, for which the chameleon mechanism does not work. We find that in such cosmological models the scalar-field potential plays a negligible role except in the background expansion, and the fifth force that is produced is proportional to gravity in magnitude, justifying the use of a rescaled gravitational constant $G$ in some earlier $N$-body simulation works for similar models. We then study the effects of the scalar coupling on the nonlinear matter power spectra and compare with linear perturbation calculations to see the agreement and places where the nonlinear treatment deviates from the linear approximation. We also propose an algorithm to identify gravitationally virialized matter halos, trying to take account of the fact that the virialization itself is also modified by the scalar-field coupling. We use the algorithm to measure the mass function and study the properties of dark-matter halos. We find that the net effect of the scalar coupling helps produce more heavy halos in our simulation boxes and suppresses the inner (but not the outer) density profile of halos compared with the $\Lambda \mathrm{CDM}$ prediction, while the suppression weakens as the coupling between the scalar field and dark-matter particles increases in strength.