The formulation of weak isolated horizons (WIH) based on the standard isolated horizon formulation of black hole horizons has been reconsidered in the context of the Holst action. Both the zeroth and the first laws of WIH mechanics have been derived. While the zeroth law follows directly from the WIH boundary conditions, first law depends on the action chosen. We construct the covariant phase space of the Holst action for a space-time having WIH as the inner boundary. This requires the introduction of new potential functions so that the symplectic structure is foliation independent. We show that a precise cancellation among various terms leads to the usual first law. Subsequently, we show from the same covariant phase space that for spherically symmetric horizons, the effective theory on the inner boundary is a $U(1)$ Chern-Simons theory.

In order to examine the gravitational waves emitted from the neutron stars in the tensor-vector-scalar (TeVeS) theory, we derive the perturbation equations for relativistic stars, where for simplicity we omit the perturbations of the vector field. That is, we consider the perturbations of scalar and tensor fields. With this assumption, we find that the axial gravitational waves, which are corresponding to the oscillations of spacetime ($w$ modes), are independent from the perturbations of the scalar field and the effects of the scalar field can be mounted only via the background properties. Using two different equations of state, we calculate the complex eigenfrequencies of axial $w$ modes and find that the dependences of frequencies on the stellar compactness are almost independent from the adopted equation of state and the parameter in TeVeS. Additionally, these dependences of frequencies of axial $w$ modes in TeVeS are obviously different from those expected in general relativity. Thus the direct observations of gravitational waves could reveal the gravitational theory in the strong-field regime.

Dark energy interacting with dark matter is a promising model to solve the cosmic coincidence problem. We study the signature of such interaction on large scale cosmic microwave background (CMB) temperature anisotropies. Based on the detail analysis in perturbation equations of dark energy and dark matter when they are in interaction, we find that the large scale CMB, especially the late integrated Sachs-Wolfe effect, is a useful tool to measure the coupling between dark sectors. We also discuss the possibility to detect the coupling by cross-correlating CMB maps with tracers of the large scale structure. We finally perform the global fitting to constrain the coupling by using the CMB power spectrum data together with other observational data. We find that in the $1\sigma$ range, the constrained coupling between dark sectors can solve the coincidence problem.

Small-field inflation typically requires rather special initial conditions to commence. It is proposed that in models where the inflaton is an axionlike field, with a periodic contribution to the potential, there is a possibility of significantly enhancing the chances of inflation without any fine-tuning of initial conditions and with no additional fine-tuning of the dynamics beyond what is needed for the potential to support inflation in the first place.

The analysis of data from gravitational wave detectors can be divided into three phases: search, characterization, and evaluation. The evaluation of the detection—determining whether a candidate event is astrophysical in origin or some artifact created by instrument noise—is a crucial step in the analysis. The ongoing analyses of data from ground-based detectors employ a frequentist approach to the detection problem. A detection statistic is chosen, for which background levels and detection efficiencies are estimated from Monte Carlo studies. This approach frames the detection problem in terms of an infinite collection of trials, with the actual measurement corresponding to some realization of this hypothetical set. Here we explore an alternative, Bayesian approach to the detection problem, that considers prior information and the actual data in hand. Our particular focus is on the computational techniques used to implement the Bayesian analysis. We find that the parallel tempered Markov chain Monte Carlo (PTMCMC) algorithm is able to address all three phases of the analysis in a coherent framework. The signals are found by locating the posterior modes, the model parameters are characterized by mapping out the joint posterior distribution, and finally, the model evidence is computed by thermodynamic integration. As a demonstration, we consider the detection problem of selecting between models describing the data as instrument noise, or instrument noise plus the signal from a single compact galactic binary. The evidence ratios, or Bayes factors, computed by the PTMCMC algorithm are found to be in close agreement with those computed using a reversible jump Markov chain Monte Carlo algorithm.

If the dark matter sector in the Universe is composed by metastable particles, galaxies and galaxy clusters are expected to undergo significant secular evolution from high to low redshift. We show that the decay of dark matter, with a lifetime compatible with cosmological constraints, can be at the origin of the observed evolution of the Tully-Fisher relation of disk galaxies and alleviate the problem of the size evolution of elliptical galaxies, while being consistent with the current observational constraints on the gas fraction of clusters of galaxies.

We perform a general chiral symmetry and unitarity based analysis of a local process of the fermion-antifermion creation from the vacuum by a high-energy photon as well as an explicit partial wave analysis of the vector current in QED and QCD. Such a local process proceeds necessarily via a certain superposition of the $S$- and $D$-wave contributions. These constraints are consistent with the well-known theoretical and experimental results on $e^{+}{e}^{-}\to \gamma \to {\mu }^{+}{\mu }^{-}$. Then a free quark loop in the $1^{--}$ channel, representing the leading term in the operator product expansion, contains both $S$-wave and $D$-wave contributions. This fact rules out the possibility that there is only one radial trajectory for the $\rho$-mesons with the fixed $S$-wave content. It also implies that all holographic models that assume a pure $S$-wave content of the $\rho$-meson have to fail to satisfy the matching conditions at the ultraviolet border $z=0$.

We consider a scenario within the minimal supersymmetric standard model (MSSM) extended by a singlet chiral superfield, in which neutralino dark matter annihilates to light singletlike Higgs bosons, which proceed to decay to either electron-positron or muon-antimuon pairs. Unlike neutralino annihilations in the MSSM, this model can provide a good fit to the PAMELA cosmic ray positron fraction excess. Furthermore, the singletlike Higgs bosons can induce a large Sommerfeld enhancement and provide an annihilation rate sufficient to accommodate the observed positron excess.

In the framework of the littlest Higgs model with $T$ parity, we study the contributions of the $T$-even and $T$-odd particles to the branching ratio $R_b$. We find that the precision data of $R_b$ can give strong constraints on the masses of $T$-odd fermions.

The short distance potentials between heavy SU(3) and SU(4) sources are calculated by increasing the role of vortex fluxes piercing Wilson loops with contributions close to the trivial center element and by fluctuating the vortex core size in the model of thick center vortices. By this method, a Coulombic potential consistent with Casimir scaling is obtained. In addition, all other features of the potential, including a linear intermediate potential in agreement with Casimir scaling and a large distance potential proportional to the $N$-ality of the representation, are restored. Therefore, the model of thick center vortices may be used as a phenomenological model, which is able to describe the potential for all regimes.

Recently, generalizations of the Ashtekar constraints are derived via the Nieh-Yan topological term. To be fair, such canonical transformations have been applied before in a gauge framework of gravity. Moreover, in the case of the teleparallelism equivalent of Einstein’s theory, one can go further and show that the Chern-Simons solutions of the Gauss-type constraints wind around torsional instantons, thus establishing an analogue to the $\theta$ vacua of Yang-Mills theory.

We show that it is both observationally allowable and theoretically possible to have large fluctuations in the dark energy equation of state as long as they occur at ultralow redshifts $z\lesssim 0.02$. These fluctuations would masquerade as a local transition in the Hubble rate of a few percent or less and escape even future, high precision, high redshift measurements of the expansion history and structure. Scalar field models that exhibit this behavior have a sharp feature in the potential that the field traverses within a fraction of an e-fold of the present. The equation of state parameter can become arbitrarily large if a sharp dip or bump in the potential causes the kinetic and potential energy of the field to both be large and have opposite sign. While canonical scalar field models can decrease the expansion rate at low redshift, increasing the local expansion rate requires a noncanonical kinetic term for the scalar field.

We discuss the impact of adiabatic renormalization on the power spectrum of scalar and tensor perturbations from inflation. We show that adiabatic regularization is ambiguous as it leads to very different results, for different adiabatic subtraction schemes, both in the range $v\equiv k/(aH)\gtrsim 0.1$ and in the infrared regime. All of these schemes agree in the far ultraviolet, $v\gg 1$. Therefore, we argue that in the far infrared regime, $v\ll 1$, the adiabatic expansion is no longer valid, and the unrenormalized spectra are the physical, measurable quantities. These findings cast some doubt on the validity of the adiabatic subtraction at horizon exit, $v=1$, to determine the perturbation spectra from inflation which has recently been advocated in the literature.

We consider a class of black holes for which the area of the two-dimensional spatial cross section has a minimum on the horizon with respect to a quasiglobal (Krusckal-like) coordinate. If the horizon is regular, one can generate a tubelike counterpart of such a metric and smoothly glue it to a black hole region. The resulting composite space-time is globally regular, so all potential singularities under the horizon of the original metrics are removed. Such a space-time represents a black hole without an apparent horizon. It is essential that the matter should be nonvacuum in the outer region but vacuumlike in the inner one. As an example we consider the noninteracting mixture of vacuum fluid and matter with a linear equation of state and scalar phantom fields. This approach is extended to distorted metrics, with the requirement of spherical symmetry relaxed.

The presence of a nonconformally invariant term in the photon sector of the Lorentz-violating extension of the standard model of particle physics, the “Kostelecký term” ${\mathcal{L}}_K\propto (k_F{)}_{\alpha \beta \mu \nu }{F}^{\alpha \beta }{F}^{\mu \nu }$, enables a superadiabatic amplification of magnetic vacuum fluctuations during de Sitter inflation. For a particular form of the external tensor $k_F$ that parametrizes Lorentz violation, the generated field possesses a planar symmetry at large cosmological scales and can have today an intensity of order of nanogauss for a wide range of values of parameters defining inflation. This peculiar magnetic field could account for the presently observed galactic magnetic fields and induces a small anisotropization of the Universe at cosmological scales. The resulting Bianchi I model could explain the presumedly low quadrupole power in the cosmic microwave background radiation.

We report on a matched-filter search for gravitational wave bursts from cosmic string cusps using LIGO data from the fourth science run (S4) which took place in February and March 2005. No gravitational waves were detected in 14.9 days of data from times when all three LIGO detectors were operating. We interpret the result in terms of a frequentist upper limit on the rate of gravitational wave bursts and use the limits on the rate to constrain the parameter space (string tension, reconnection probability, and loop sizes) of cosmic string models. Many grand unified theory-scale models (with string tension $G\mu /c^2\approx {10}^{-6}$) can be ruled out at 90% confidence for reconnection probabilities $p\le {10}^{-3}$ if loop sizes are set by gravitational back reaction.

We propose an unified model of dark matter and baryon asymmetry in a leptophilic world above the electroweak scale. We provide an example where the inflaton decay products subsequently generate a lepton asymmetry and a dark matter abundance with an unique coupling in the early Universe, while the present day decay of the dark matter through the same coupling gives rise the observed cosmic ray anomalies at PAMELA and Fermi Large Area Telescope.

The trace anomaly of gluodynamics on the lattice shows clear fingerprints of a dimension two condensate above the phase transition. The condensate manifests itself through even powers of the inverse temperature while the total perturbative contribution corresponds to a mild temperature dependence and turns out to be compatible with zero within errors. We try several resummation methods based on a renormalization group improvement. The trace anomaly data are analyzed and compared with other determinations of the dimension two condensate based on the Polyakov loop and the heavy $q\overline{q}$ free energy, yielding roughly similar numerical values. The role of glueballs near the transition is also discussed.

We investigate the prospects for indirect detection of right-handed sneutrino dark matter at the IceCube neutrino telescope in a $U(1{)}_{B-L}$ extension of the minimal supersymmetric standard model. The capture and annihilation of sneutrinos inside the Sun reach equilibrium, and the flux of produced neutrinos is governed by the sneutrino-proton elastic scattering cross section, which has an upper bound of $8\times {10}^{-9}\mathrm{pb}$ from the $Z^{\prime }$ mass limits in the $B-L$ model. Despite the absence of any spin-dependent contribution, the muon event rates predicted by this model can be detected at IceCube since sneutrinos mainly annihilate into leptonic final states by virtue of the fermion $B-L$ charges. These subsequently decay to neutrinos with 100% efficiency. The Earth muon event rates are too small to be detected for the standard halo model irrespective of an enhanced sneutrino annihilation cross section that can explain the recent PAMELA data. For modified velocity distributions, the Earth muon events increase substantially and can be greater than the IceCube detection threshold of 12 events ${\mathrm{km}}^{-2}{\mathrm{yr}}^{-1}$. However, this only leads to a mild increase of about 30% for the Sun muon events. The number of muon events from the Sun can be as large as roughly 100 events ${\mathrm{km}}^{-2}{\mathrm{yr}}^{-1}$ for this model.

We study the neutron electric dipole moment (EDM) in a five-dimensional $SU(3)$ gauge-Higgs unification compactified on $M^4\times S^1/Z_2$ space-time including a massive fermion. We point out that to realize the $CP$ violation is a nontrivial task in the gauge-Higgs unification scenario and argue how the $CP$ symmetry is broken spontaneously by the vacuum expectation value of the Higgs, the extra space component of the gauge field. We emphasize the importance of the interplay between the vacuum expectation value of the Higgs and the $Z_2$-odd bulk mass term to get physically the $CP$ violation. We then calculate the one-loop contributions to the neutron EDM as the typical example of the $CP$ violating observable and find that the EDM appears already at the one-loop level, without invoking the three-generation scheme. We then derive a lower bound for the compactification scale, which is around 2.6 TeV, by comparing the contribution due to the nonzero Kaluza-Klein modes with the experimental data.