I discuss the possibility of topological defect solutions in field theories containing a tensor field which spontaneously breaks Lorentz symmetry. I find that for theories of a tensor with rank $r\le 5$ and for which the vacuum manifold consists of the tensors whose “square” is some constant value, only three types of tensor (vectors, antisymmetric two-tensors, and symmetric two-tensors) have the appropriate vacuum manifold topology to support topological defects. Of these, topological defect solutions can be easily constructed for two: vector domain-wall solutions and antisymmetric tensor monopole solutions. These antisymmetric tensor monopole solutions are in principle detectible via their gravitational lensing effects.

We study the infrared (IR) limit of dispersion relations for scalar and fermion fields in a Lifshitz-type Yukawa model, after dressing by quantum fluctuations. Relativistic-like dispersion relations emerge dynamically in the IR regime of the model, after quantum corrections are taken into account. In this regime, dynamical mass generation also takes place, but in such a way that the particle excitations remain massive, even if the bare masses vanish. The group velocities of the corresponding massive particles of course are smaller than the speed of light, in a way consistent with the IR regime where the analysis is performed. We also comment on possible extensions of the model where the fermions are coupled to an Abelian gauge field.

By studying the notion of a fundamentally minimal length scale in asymptotically safe gravity we find that a specific version of deformed special relativity (DSR) naturally arises in this approach. We then consider two thought experiments to examine the interpretation of the scenario and discuss similarities and differences to other approaches to DSR.

We develop techniques of analyzing the unitarity of general Born-Infeld gravity actions in $D$-dimensional spacetimes. The determinantal form of the action allows us to find a compact expression quadratic in the metric fluctuations around constant curvature backgrounds. This is highly nontrivial since for the Born-Infeld actions, in principle, infinitely many terms in the curvature expansion should contribute to the quadratic action in the metric fluctuations around constant curvature backgrounds, which would render the unitarity analysis intractable. Moreover in even dimensions, unitarity of the theory depends only on finite number of terms built from the powers of the curvature tensor. We apply our techniques to some four-dimensional examples.

Motivated by recent interest in applications of the AdS/CFT correspondence to condensed matter applications involving fermions, we present the supersymmetric completion of the recent massive truncations of IIB supergravity on Sasaki-Einstein manifolds. In particular, we reduce the fermionic sector of IIB supergravity to obtain five-dimensional $\mathcal{N}=2$ supergravity coupled to one hypermultiplet and one massive vector multiplet. The supersymmetry transformations and equations of motion are presented and analyzed. Finally, a particularly interesting truncation to $\mathcal{N}=2$ supergravity coupled to a single hypermultiplet is presented which is the supersymmetric completion of the recently constructed bosonic theory dual to a $3+1$ dimensional system exhibiting a superconducting phase transition.

We generalize the notion of a dielectric analog Schwarzschild black hole model to analog models of arbitrary space-times; in particular, the approach is not restricted to static space-times. This is done by establishing a correspondence between electrodynamics on a curved, vacuum manifold, with electrodynamics in a general linear dielectric residing in Minkowski space-time. The mapping is not unique, allowing for some freedom in the specification of equivalent materials, which could be useful for exploiting recent developments in the production of metamaterials. Some examples are considered, with special attention paid to the dielectric analog of the exterior Kerr geometry, which is found to be reproducible with regular, linear, dielectrics.

Here we show how an anisotropic fluid in the diffusion limit can be equivalent to an isotropic fluid in the streaming out limit, in spherical symmetry. For a particular equation of state this equivalence is total: from one fluid we can obtain the other and vice versa. A numerical master model is presented, based on a generic equation of state, in which only quantitative differences are displayed between both nonadiabatic fluids. From a deeper view, another difference between fluids is shown as an asymmetry that can be overcome if we consider the appropriate initial-boundary conditions. Equivalence in this context can be considered as a first order method of approximation to study dissipative fluids.

In this paper we show that the mass-energy density of the Universe can be fully determined in terms of the cosmological redshifts, their time drifts and angular-diameter distance (observer area distance). Besides providing an indirect measurement of the mass-energy density of the Universe, we show how one can use the time-drift of the cosmological redshifts as a replacement for the mass-energy density element in the minimally required data set to construct an spherically symmetric Lemaître-Tolman-Bondi model for the Universe in observational coordinates.

Several years ago, two of the present authors proposed the concept of the border of spacetime as a generalization of spacetime singularities. Visible borders of spacetime, which replace naked singularities of classical theory, are not only necessary for the mathematical completeness of general relativity but they also provide a window into new physics of strongly curved spacetime, which is observable in principle. By employing simple geometrical and dimensional arguments, we show that not only black holes but also visible borders of spacetime will be generated at, for example, the CERN Large Hadron Collider, provided that the energy scale of quantum gravity is near 1 TeV in the framework of the large extra-dimension scenario.

The charged fermion mass matrices are always invariant under $U(1{)}^3$ symmetry linked to the fermion number transformation. A class of two-Higgs-doublet models can be identified by requiring that the definition of this symmetry in an arbitrary weak basis be independent of Higgs parameters such as the ratio of the Higgs vacuum expectation values. The tree-level flavor changing neutral currents normally present in two-Higgs-doublet models are absent in this class of models, but unlike the type-I or type-II Higgs doublet models, the charged Higgs couplings in these models contain additional flavor-dependent CP-violating phases. These phases can account for the recent hints of the beyond-standard-model CP violation in the $B_d$ and $B_s$ mixing. In particular, there is a range of parameters in which new phases do not contribute to the $K$meson CP violation but give identical new physics contribution to the $B_d$ and $B_s$meson mixing. Specific model realizations of the above scenario are briefly discussed.

We calculated the cross section for the exclusive double-diffractive $b\overline{b}$ production in $pp\to p(b\overline{b})p$ reaction at LHC. Large cross sections are obtained (3–10 nb). This process constitutes the irreducible background to the exclusive Higgs production and is of particular importance in the upcoming Higgs boson searches. The distribution in invariant mass of the $b\overline{b}$ pair is calculated and compared with the corresponding contribution from the Higgs decay. The contribution from the exclusive production of $Z^0$ and its decay as well as the contribution from the $\gamma \gamma \to b\overline{b}$ subprocess are also presented for the first time. The influence of cuts on the signal-to-background ratio is discussed.

We report on a measurement of the fraction of events with a $W$ or $Z$ boson which are produced diffractively in $\overline{p}p$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$, using data from $0.6{\mathrm{fb}}^{-1}$ of integrated luminosity collected with the CDF II detector equipped with a Roman-pot spectrometer that detects the $\overline{p}$ from $\overline{p}+p\to \overline{p}+[X+W/Z]$. We find that $(1.00\pm 0.11)\%$ of $W$s and $(0.88\pm 0.22)\%$ of $Z$s are produced diffractively in a region of antiproton or proton fractional momentum loss $\xi$ of $0.03<\xi <0.10$ and 4-momentum transferred squared $t$ of $-1<t<0(\mathrm{GeV}/c{)}^2$, where we account for the events in which the proton scatters diffractively while the antiproton dissociates, $\overline{p}+p\to [X+W/Z]+p$, by doubling the measured proton dissociation fraction. We also report on searches for $W$ and $Z$ production in double Pomeron exchange, $p+\overline{p}\to p+[X+W/Z]+\overline{p}$, and on exclusive $Z$ production, $\overline{p}+p\to \overline{p}+Z+p$. No signal is seen above background for these processes, and comparisons are made with expectations.

In this paper, we discuss the issues of supersymmetry breaking and moduli stabilization within the context of $E_8\otimes E_8$ heterotic orbifold constructions and, in particular, we focus on the class of “mini-landscape” models. In the supersymmetric limit, these models admit an effective low-energy field theory with a spectrum of states and dimensionless gauge and Yukawa couplings very much like that of the minimal supersymmetric standard model. These theories contain a non-Abelian hidden gauge sector which generates a nonperturbative superpotential leading to supersymmetry breaking and moduli stabilization. We demonstrate this effect in a simple model which contains many of the features of the more general construction. In addition, we argue that once supersymmetry is broken in a restricted sector of the theory, then all moduli are stabilized by supergravity effects. Finally, we obtain the low-energy superparticle spectrum resulting from this simple model.

Large-$N$ QCD with heavy adjoint fermions emulates pure Yang-Mills theory at long distances. We study this theory on a four- and three-torus, and analytically argue the existence of a large-small volume equivalence. For any finite mass, the center-symmetry unbroken phase exists at sufficiently small volume and this phase can be used to study the large volume limit through the Eguchi-Kawai equivalence. A finite-temperature version of volume independence implies that thermodynamics on ${\mathbb{R}}^3\times S^1$ can be studied via a unitary matrix quantum mechanics on $S^1$, by varying the temperature. To confirm this nonperturbatively, we numerically study both zero- and one-dimensional theories by using Monte Carlo simulation. The order of finite-$N$ corrections turns out to be $1/N$. We introduce various twisted versions of the reduced QCD which systematically suppress finite-$N$ corrections. Using a twisted model, we observe the confinement/deconfinement transition on a $1^3\times 2$ lattice. The result agrees with large volume simulations of Yang-Mills theory. We also comment that the twisted model can serve as a nonperturbative formulation of the noncommutative Yang-Mills theory.

Current-carrying string loop dynamics in Schwarzschild-de Sitter spacetimes characterized by the cosmological parameter $\lambda =\frac{1}{3}\Lambda M^2$ is investigated. With attention concentrated to the axisymmetric motion of string loops it is shown that the resulting motion is governed by the presence of an outer tension barrier and an inner angular momentum barrier that are influenced by the black hole gravitational field given by the mass $M$ and the cosmic repulsion given by the cosmological constant $\Lambda$. The gravitational attraction could cause capturing of the string having low energy by the black hole or trapping in its vicinity; with high enough energy, the string can escape (scatter) to infinity. The role of the cosmic repulsion becomes important in vicinity of the so-called static radius where the gravitational attraction is balanced by the cosmic repulsion—it is demonstrated both in terms of the effective potential of the string motion and the basin boundary method reflecting its chaotic character, that a potential barrier exists along the static radius behind which no trapped oscillations may exist. The trapped states of the string loops, governed by the interplay of the gravitating mass $M$ and the cosmic repulsion, are allowed only in Schwarzschild-de Sitter spacetimes with the cosmological parameter $\lambda <{\lambda }_{\mathrm{trap}}\sim 0.00497$. The trapped oscillations can extend close to the radius of photon circular orbit, down to $r_{\mathrm{mt}}\sim 3.3M$.

The generalized second law is proven for rapidly evolving semiclassical Rindler horizons at each instant of time, for arbitrary interacting quantum fields minimally coupled to general relativity. The proof requires the background spacetime to have both boost and null translation symmetry. Possible extensions to more general horizons and matter-gravity couplings are discussed.

In standard models of baryogenesis and of dark matter, the mechanisms which generate the densities in both sectors are unrelated to each other. In this paper we explore models which generate the baryon asymmetry through the dark matter sector, simultaneously relating the baryon asymmetry to the dark matter density. In the class of models we explore, a dark matter asymmetry is generated in the hidden sector through a first-order phase transition. Within the hidden sector, it is easy to achieve a sufficiently strong first-order phase transition and large enough $CP$ violation to generate the observed asymmetry. This can happen above or below the electroweak phase transition, but in both cases significantly before the dark matter becomes nonrelativistic. We study examples where the asymmetric dark matter density is then transferred to the baryons both through perturbative and nonperturbative communication mechanisms, and show that in both cases cosmological constraints are satisfied while a sufficient baryon asymmetry can be generated.

We study how well the mass of the graviton can be constrained from gravitational-wave (GW) observations of coalescing binary black holes. Whereas the previous investigations employed post-Newtonian (PN) templates describing only the inspiral part of the signal, the recent progress in analytical and numerical relativity has provided analytical waveform templates coherently describing the inspiral-merger-ringdown (IMR) signals. We show that a search for binary black holes employing IMR templates will be able to constrain the mass of the graviton much more accurately ($\sim$ an order of magnitude) than a search employing PN templates. The best expected bound from GW observatories (${\lambda }_g>7.8\times {10}^{13}\mathrm{km}$ from Advanced LIGO, ${\lambda }_g>7.1\times {10}^{14}\mathrm{km}$ from Einstein Telescope, and ${\lambda }_g>5.9\times {10}^{17}\mathrm{km}$ from LISA) are several orders of magnitude better than the best available model-independent bound (${\lambda }_g>2.8\times {10}^{12}\mathrm{km}$, from solar system tests).

In this paper we discuss two mechanisms by which high-energy electrons resulting from dark matter annihilations in or near the Sun can arrive at the Earth. Specifically, electrons can escape the Sun if DM annihilates into long-lived states, or if dark matter scatters inelastically, which would leave a halo of dark matter outside of the Sun. Such a localized source of electrons may affect the spectra observed by experiments with narrower fields of view oriented towards the Sun, such as ATIC, differently from those with larger fields of view such as Fermi. We suggest a simple test of these possibilities with existing Fermi data that is more sensitive than limits from final state radiation. If observed, such a signal will constitute an unequivocal signature of dark matter.