The direct interaction of the 4-rotational (Lorentzian) gauge field with angular orbital momentum of an external field is considered. This interaction appears in a new Poincaré gauge theory of gravitation, in which tetrads are not true gauge fields, but represent some functions of the translational and 4-rotational gauge fields. The given interaction leads to a new effect: the existence of an electronic orbit precession under the action of an intensive external gravitational field (gravidiamagnetic effect), and also substantiates the existence of the direct interaction of the proper angular momentum of a gyroscope with the torsion field, which theoretically can be generated by the rotational angular momentum of the planet Earth. The latter interaction can be detected by the experiment Gravity Probe B on the satellite orbit.

Using gauge/gravity duality, we study the creation and evolution of boost-invariant anisotropic, strongly-coupled $\mathcal{N}=4$ supersymmetric Yang-Mills plasma. In the dual gravitational description, this corresponds to horizon formation in a geometry driven to be anisotropic by a time-dependent change in boundary conditions.

We show how the recently proposed Taylor-Lagrange renormalization scheme can lead to extensions of singular distributions which are reminiscent of the Pauli-Villars subtraction. However, at variance with the Pauli-Villars regularization scheme, no infinite mass limit is performed in this scheme. As an illustration of this mechanism, we consider the calculation of the self-energy in second order perturbation theory in the Yukawa model, within the covariant formulation of light-front dynamics. We show, in particular, how rotational invariance is preserved in this scheme.

We address a number of unanswered questions in the $\mathcal{N}=(0,2)$-deformed $CP(N-1)$ model with twisted masses. In particular, we complete the program of solving the $CP(N-1)$ model with twisted masses in the large-$N$ limit. In A. Gorsky, M. Shifman, and A. Yung, Phys. Rev. D 73, 065011 (2006), a nonsupersymmetric version of the model with the $Z_N$ symmetric twisted masses was analyzed in the framework of Witten’s method. In M. Shifman and A. Yung, Phys. Rev. D 77, 125017 (2008), this analysis was extended: the large-$N$ solution of the heterotic $\mathcal{N}=(0,2)$ $CP(N-1)$ model with no twisted masses was found. Here we solve this model with the twisted masses switched on. Dynamical scenarios at large and small $m$ are studied ($m$ is the twisted-mass scale). We found three distinct phases and two phase transitions on the $m$ plane. Two phases with the spontaneously broken $Z_N$ symmetry are separated by a phase with unbroken $Z_N$. This latter phase is characterized by a unique vacuum and confinement of all U(1) charged fields (“quarks”). In the broken phases (one of them is at strong coupling) there are $N$ degenerate vacua and no confinement, similarly to the situation in the $\mathcal{N}=(2,2)$ model. Supersymmetry is spontaneously broken everywhere except a circle $|m|=\Lambda$ in the $Z_N$-unbroken phase. Related issues are considered. In particular, we discuss the mirror representation for the heterotic model in a certain limiting case.

We present two results on the recently proposed new spin foam models. First, we show how a (slightly modified) restriction on representations in the Engle-Pereira-Rovelli-Livine model leads to the appearance of the Ashtekar-Barbero connection, thus bringing this model even closer to loop quantum gravity. Second, we however argue that the quantization procedure used to derive the new models is inconsistent since it relies on the symplectic structure of the unconstrained BF theory.

We consider the three-point function (i.e. the bispectrum or non-Gaussianity) for stochastic backgrounds of gravitational waves. We estimate the amplitude of this signal for the primordial inflationary background, gravitational waves generated during preheating, and for gravitational waves produced by self-ordering scalar fields following a global phase transition. To assess detectability, we describe how to extract the three-point signal from an idealized interferometric experiment and compute the signal to noise ratio as a function of integration time. The three-point signal for the stochastic gravitational wave background generated by inflation is unsurprisingly tiny. For gravitational radiation generated by purely causal, classical mechanisms we find that, no matter how nonlinear the process is, the three-point correlations produced vanish in direct detection experiments. On the other hand, we show that in scenarios where the $B$-mode of the cosmic microwave background is sourced by gravitational waves generated by a global phase transition, a strong three-point signal among the polarization modes is also produced. This may provide another method of distinguishing inflationary $B$-modes. To carry out this computation, we have developed a diagrammatic approach to the calculation of stochastic gravitational waves sourced by scalar fluids, which has applications beyond the present scenario.

The possibility of reconstructing a spherically symmetric inhomogeneous Lemaître-Tolman-Bondi (LTB) model with $\Lambda \mathrm{CDM}$ observations has drawn much attention. Recently, an inhomogeneous LTB model having the same luminosity-distance and light-cone mass density of the homogeneous $\Lambda \mathrm{CDM}$ model was reconstructed. From the Wilkinson microwave anisotropy probe 7-year measurements together with other cosmological observations, we calculate the cosmic age at our position in this LTB model, and obtain a constraint $t_{\mathrm{LTB}}<11.7\mathrm{Gyr}$ at $1\sigma$ confidence level. We find that this result is, although 2 Gyr younger compared with the age of the homogeneous $\Lambda \mathrm{CDM}$ model, still within $1\sigma$ agreement with the constraint of cosmic age given by current astronomical measurements. We expect that in the future, with the help of more advanced observations, we can distinguish the reconstructed inhomogeneous LTB model from the homogeneous $\Lambda \mathrm{CDM}$ model.

Stochastic effects during inflation can be addressed by averaging the quantum inflaton field over Hubble-patch–sized domains. The averaged field then obeys a Langevin-type equation into which short-scale fluctuations enter as a noise term. We solve the Langevin equation for an inflaton field with a Dirac-Born-Infeld (DBI) kinetic term perturbatively in the noise and use the result to determine the field value’s probability density function (PDF). In this calculation, both the shape of the potential and the warp factor are arbitrary functions, and the PDF is obtained with and without volume effects due to the finite size of the averaging domain. DBI kinetic terms typically arise in string-inspired inflationary scenarios in which the scalar field is associated with some distance within the (compact) extra dimensions. The inflaton’s accessible range of field values therefore is limited because of the extra dimensions’ finite size. We argue that in a consistent stochastic approach the inflaton’s PDF must vanish for geometrically forbidden field values. We propose to implement these extra-dimensional spatial restrictions into the PDF by installing absorbing (or reflecting) walls at the respective boundaries in field space. As a toy model, we consider a DBI inflaton between two absorbing walls and use the method of images to determine its most general PDF. The resulting PDF is studied in detail for the example of a quartic warp factor and a chaotic inflaton potential. The presence of the walls is shown to affect the inflaton trajectory for a given set of parameters.

It has recently been proposed that the large-scale bias of dark matter halos depends sensitively on primordial non-Gaussianity of the local form. In this paper we point out that the strong scale dependence of the non-Gaussian halo bias imprints a distinct signature on the covariance of cluster counts. We find that using the full covariance of cluster counts results in improvements on constraints on the non-Gaussian parameter $f_{\mathrm{NL}}$ of 3 (1) orders of magnitude relative to cluster counts ($\mathrm{\text{counts}}+\mathrm{\text{clustering variance}}$) constraints alone. We forecast $f_{\mathrm{NL}}$ constraints for the upcoming Dark Energy Survey in the presence of uncertainties in the mass-observable relation, halo bias, and photometric redshifts. We find that the Dark Energy Survey can yield constraints on non-Gaussianity of $\sigma (f_{\mathrm{NL}})\sim 1–5$ even for relatively conservative assumptions regarding systematics. Excess of correlations of cluster counts on scales of hundreds of megaparsecs would represent a smoking-gun signature of primordial non-Gaussianity of the local type.

We emphasize that the stabilizing symmetry for dark matter (DM) particles does not have to be the commonly used parity ($Z_2$) symmetry. We therefore examine the potential of the colliders to distinguish models with parity stabilized DM from models in which the DM is stabilized by other symmetries. We often take the latter to be a $Z_3$ symmetry for illustration. We focus on signatures where a single particle, charged under the DM stabilization symmetry decays into the DM and standard model (SM) particles. Such a $Z_3$-charged mother particle can decay into one or two DM particles along with the same SM particles. This can be contrasted with the decay of a $Z_2$-charged mother particle, where only one DM particle appears. Thus, if the intermediate particles in these decay chains are off-shell, then the reconstructed invariant mass of the SM particles exhibits two kinematic edges for the $Z_3$ case but only one for the $Z_2$ case. For the case of on-shell intermediate particles, distinguishing the two symmetries requires more than the kinematic edges. In this case, we note that certain decay chain topologies of the mother particle which are present for the $Z_3$ case (but absent for the $Z_2$ case) generate a cusp in the invariant mass distribution of the SM particles. We demonstrate that this cusp is generally invariant of the various spin configurations. We further apply these techniques within the context of explicit models.

For a class of hindered magnetic-dipole ($M1$) transition processes, such as ${\rm Y}(3S)\to {\eta }_b+\gamma$ (the discovery channel of the ${\eta }_b$ meson), the emitted photon is rather energetic so that the traditional approaches based on multipole expansion may be invalidated. We propose that a “hard-scattering” picture, somewhat analogous to the pion electromagnetic form factor at large momentum transfer, may be more plausible to describe such types of transition processes. We work out a simple factorization formula at lowest order in the strong coupling constant, which involves convolution of the Schrödinger wave functions of quarkonia with a perturbatively calculable part induced by exchange of one semihard gluon between quark and antiquark. This formula, without any freely adjustable parameters, is found to agree with the measured rate of ${\rm Y}(3S)\to {\eta }_b+\gamma$ rather well, and can also reasonably account for other recently measured hindered $M1$ transition rates. The branching fractions of ${\rm Y}(4S)\to {\eta }_b^{(\prime )}+\gamma$ are also predicted.

We present a study of axial charges of baryon ground and resonant states with relativistic constituent quark models. In particular, the axial charges of octet and decuplet $N$, $\Sigma$, $\Xi$, $\Delta$, ${\Sigma }^{*}$, and ${\Xi }^{*}$ baryons are considered. The theoretical predictions are compared to existing experimental data and results from other approaches, notably from lattice quantum chromodynamics and chiral perturbation theory. The relevance of axial charges with regard to $\pi$-dressing and spontaneous chiral-symmetry breaking is discussed.

In the present paper, a new class of black hole solutions is constructed in even dimensional Lovelock Born-Infeld theory. These solutions are interesting since, in some respects, they are closer to black hole solutions of an odd dimensional Lovelock Chern-Simons theory than to the more usual black hole solutions in even dimensions. This hybrid behavior arises when non-Einstein base manifolds are considered. The entropies of these solutions have been analyzed using Wald formalism. These metrics exhibit a quite nontrivial behavior. Their entropies can change sign and can even be identically zero depending on the geometry of the corresponding base manifolds. Therefore, the request of thermodynamical stability constrains the geometry of the non-Einstein base manifolds. It will be shown that some of these solutions can support nonvanishing torsion. Eventually, the possibility to define a sort of topological charge associated with torsion will be discussed.

We consider extensions of Lemaitre-Tolman-Bondi (LTB) spacetimes to the dissipative case. We have previously carried out a systematic study on LTB. This study is based on two different aspects of LTB. On the one hand, a symmetry property of LTB will be presented. On the other hand, the description of LTB in terms of some fundamental scalar functions (structure scalars) appearing in the orthogonal splitting of Riemann tensor will be provided. We shall consider as natural generalizations of LTB (hereafter referred to as GLTB) either those metrics admitting some similar kind of symmetry as LTB, or those sharing structure scalars with similar dependence on the metric.

The static vacuum spherically symmetric solutions of massive gravity theories possess two integration constants: the mass $M$ and a scalar charge $S$. The presence of this scalar charge reflects the modification of the gravitational interaction as compared to general relativity. Surprisingly, these solutions have an asymptotic behavior different from that obtained in the linear perturbation theory. The aim of this paper is to understand how these modified spherically symmetric solutions emerge from a quasilinear approximation in order to generalize them to any arbitrary mass distribution. Along with these modified solutions, we found a new class of static solutions having a Yukawa shape.

We investigate the instanton solution between the degenerate vacua in curved space. We show that there exist $O(4)$-symmetric solutions not only in de Sitter but also in both flat and anti–de Sitter space. The geometry of the new type of solutions is finite and preserves the $Z_2$ symmetry. The nontrivial solution corresponding to the tunneling is possible only if gravity is taken into account. The numerical solutions as well as the analytic computations using the thin-wall approximation are presented. We expect that these solutions do not have any negative mode as in the instanton solution.

Effects of quantized free scalar fields in cosmological spacetimes with big rip singularities are investigated. The energy densities for these fields are computed at late times when the expansion is very rapid. For the massless minimally coupled field it is shown that an attractor state exists in the sense that, for a large class of states, the energy density of the field asymptotically approaches the energy density it would have if it was in the attractor state. Results of numerical computations of the energy density for the massless minimally coupled field and for massive fields with minimal and conformal couplings to the scalar curvature are presented. For the massive fields the energy density is seen to always asymptotically approach that of the corresponding massless field. The question of whether the energy densities of quantized fields can be large enough for backreaction effects to remove the big rip singularity is addressed.

We consider a class of late-decaying dark matter models, in which a dark matter particle decays to a heavy stable daughter of approximately the same mass, together with one or more relativistic particles which carry away only a small fraction of the parent rest mass. Such decays can affect galactic halo structure and evolution, and have been invoked as a remedy to some of the small-scale structure formation problems of cold dark matter. There are existing stringent limits on the dark matter lifetime if the decays produce photons. By considering examples in which the relativistic decay products instead consist of neutrinos or electron-position pairs, we derive stringent limits on these scenarios for a wide range of dark matter masses. We thus eliminate a sizable portion of the parameter space for these late-decay models if the dominant decay channel involves standard model final states.

We calculate a signature of cosmic strings in the polarization of the cosmic microwave background. We find that ionization in the wakes behind moving strings gives rise to extra polarization in a set of rectangular patches in the sky whose length distribution is scale-invariant. The length of an individual patch is set by the comoving Hubble radius at the time the string is perturbing the cosmic microwave background. The polarization signal is largest for string wakes produced at the earliest post-recombination time, and for an alignment in which the photons cross the wake close to the time the wake is created. The maximal amplitude of the polarization relative to the temperature quadrupole is set by the overdensity of free electrons inside a wake which depends on the ionization fraction $f$ inside the wake. For a cosmic string wake coming from an idealized string segment, the signal can be as high as $0.06\mu \mathrm{K}$ in degree scale polarization for a string at high redshift (near recombination) and a string tension $\mu$ given by $G\mu ={10}^{-7}$.

We demonstrate a new model which uses an Arkani-Hamed–Dimopoulos–Dvali type braneworld scenario to produce a multistate theory of dark matter. Compactification of the extra dimensions onto a sphere leads to the association of a single complex scalar in the bulk with multiple Kaluza-Klein towers in an effective four-dimensional theory. A mutually interacting multistate theory of dark matter arises naturally within which the dark matter states are identified with the lightest Kaluza-Klein particles of fixed magnetic quantum number. These states are protected from decay by a combination of a global $U(1)$ symmetry and the continuous rotational symmetry about the polar axis of the spherical geometry. We briefly discuss the relic abundance calculation and investigate the spin-independent elastic scattering off nucleons of the lightest and next-to-lightest dark matter states.