We find topological (charged) black holes whose horizon has an arbitrary constant scalar curvature $2k$ in Hořava-Lifshitz theory. Without loss of generality, one may take $k=1$, 0, and $-1$. The black hole solution is asymptotically anti–de Sitter with a nonstandard asymptotic behavior. Using the Hamiltonian approach, we define a finite mass associated with the solution. We discuss the thermodynamics of the topological black holes and find that the black hole entropy has a logarithmic term in addition to an area term. We find a duality in Hawking temperature between topological black holes in Hořava-Lifshitz theory and Einstein’s general relativity: the temperature behaviors of black holes with $k=1$, 0, and $-1$ in Hořava-Lifshitz theory are, respectively, dual to those of topological black holes with $k=-1$, 0, and 1 in Einstein’s general relativity. The topological black holes in Hořava-Lifshitz theory are thermodynamically stable.

We investigate the appearance of the classical anisotropic universe from the no-boundary quantum state according to the prescription proposed by Hartle, Hawking, and Hertog. Our model is homogeneous, anisotropic, closed universes with a minimally coupled scalar field and cosmological constant. We found that there are an ensemble of classical Lorentzian histories with anisotropies and experience inflationary expansion at late time, and the probability of histories with anisotropies are lower than isotropic histories. Thus, the no-boundary condition may be able to explain the emergence of our Universe. If the classical late time histories are extended back, some become singular by the existence of initial anisotropies with large accelerations. However, we do not find any chaotic behavior of anisotropies near the initial singularity.

As an extension of the cosmological constant model ($\Lambda \mathrm{CDM}$), the decaying vacuum (DV) model describes dark energy as a varying vacuum whose energy density decays linearly with the Hubble parameter at late times, ${\rho }_{\Lambda }(t)\propto H(t)$, and produces the matter component. We examine the high-$z$ cosmic age problem in the DV model, and compare it with $\Lambda \mathrm{CDM}$ and the Yang-Mills condensate (YMC) dark energy model. Without employing a dynamical scalar field for dark energy, these three models share a similar behavior of late-time evolution. It is found that the DV model, like the YMC, can accommodate the high-$z$ quasar APM $08279+5255$, thus greatly alleviating the high-$z$ cosmic age problem. We also calculate the statefinder $(r,s)$ and the $Om$ diagnostics in the model. It is found that the evolutionary trajectories of $r(z)$ and $s(z)$ in the DV model are similar to those in the kinessence model, but are distinguished from those in $\Lambda \mathrm{CDM}$ and the YMC. The $Om(z)$ in the DV model has a negative slope and its height depends on the matter fraction, while the YMC has a rather flat $Om(z)$, whose magnitude depends sensitively on the coupling.

Cosmological constraints from the cosmic microwave background (CMB) anisotropies rely on accurate theoretical calculations of the cosmic recombination history. Recent work has emphasized the importance of radiative transfer calculations due to the high optical depth in the H i Lyman lines. Transfer in the $\mathrm{Ly}\alpha$ line is dominated by true emission and absorption, Hubble expansion, and resonant scattering. Resonant scattering causes photons to diffuse in frequency due to random kicks from the thermal velocities of hydrogen atoms, and also to drift toward lower frequencies due to energy loss via atomic recoil. Past analyses of $\mathrm{Ly}\alpha$ transfer during the recombination era have either considered a subset of these processes, ignored time dependence, or incorrectly assumed identical emission and absorption profiles. We present here a fully time-dependent radiative transfer calculation of the $\mathrm{Ly}\alpha$ line including all of these processes, and compare it to previous results that ignored the resonant scattering. We find a faster recombination due to recoil enhancement of the $\mathrm{Ly}\alpha$ escape rate, leading to a reduction in the free electron density of 0.45% at $z=900$. This results in an increase in the small-scale CMB power spectrum that is negligible for the current data but will be a $0.9\sigma$ correction for Planck. We discuss the reasons why we find a smaller correction than some other recent computations.

We present atom-interferometer tests of the local Lorentz invariance of post-Newtonian gravity. An experiment probing for anomalous vertical gravity on Earth, which has already been performed, uses the highest-resolution atomic gravimeter so far. The influence of Lorentz violation in electrodynamics is also taken into account, resulting in combined bounds on Lorentz violation in gravity and electrodynamics. Expressed within the standard model extension or Nordtvedt’s anisotropic universe model, we limit 12 linear combinations of seven coefficients for Lorentz violation at the part per billion level, from which we derive limits on six coefficients (and seven when taking into account additional data from lunar laser ranging). We also discuss the use of horizontal interferometers, including atom-chip or guided-atom devices, which potentially allow the use of longer coherence times in order to achieve higher sensitivity.

A dark sector—a new non-Abelian gauge group Higgsed or confined near the GeV scale—can be spectacularly probed in low-energy $e^{+}{e}^{-}$ collisions. A low-mass dark sector can explain the annual modulation signal reported by DAMA/LIBRA and the PAMELA, ATIC, and INTEGRAL observations by generating small mass splittings and new interactions for weak-scale dark matter. Some of these observations may be the first signs of a low-mass dark sector that collider searches can definitively confirm. Production and decay of $\mathcal{O}(\mathrm{GeV})$-mass dark states is mediated by a Higgsed Abelian gauge boson that mixes kinetically with hypercharge. Existing data from BABAR, BELLE, CLEO-c, and KLOE may contain thousands of striking dark-sector events with a high multiplicity of leptons that reconstruct mass resonances and possibly displaced vertices. We discuss the production and decay phenomenology of Higgsed and confined dark sectors and propose $e^{+}{e}^{-}$ collider search strategies. We also use the DAMA/LIBRA signal to estimate the production cross sections and decay lifetimes for dark-sector states.

The study of displaced vertices containing two b-jets may provide a double discovery at the Large Hadron Collider (LHC): we show how it may not only reveal evidence for supersymmetry, but also provide a way to uncover the Higgs boson necessary in the formulation of the electroweak theory in a large region of the parameter space. We quantify this explicitly using the simplest minimal supergravity model with bilinear breaking of R-parity, which accounts for the observed pattern of neutrino masses and mixings seen in neutrino oscillation experiments.

The minimal supersymmetric extension of the standard model provides a solution to the hierarchy problem and leads to the presence of a light Higgs. A Higgs boson with mass above the present experimental bound may only be obtained for relatively heavy third generation squarks, requiring a precise, somewhat unnatural balance between different contributions to the effective Higgs mass parameter. It was recently noticed that somewhat heavier Higgs bosons, which are naturally beyond the CERN LEP bound, may be obtained by enhanced weak $SU(2)$ D-terms. Such contributions appear in models with an enhanced electroweak gauge symmetry, provided the supersymmetry breaking masses associated with the scalars responsible for the breakdown of the enhanced gauge symmetry group to the standard model one are larger than the enhanced symmetry breaking scale. In this article we emphasize that the enhanced $SU(2)$ D-terms will not only raise the Higgs boson mass but also affect the spectrum of the nonstandard Higgs bosons, sleptons, and squarks, which therefore provide a natural contribution to the $T$ parameter, compensating for the negative one coming from the heavy Higgs boson. The sleptons and nonstandard Higgs bosons of these models, in particular, may act in a way similar to the so-called inert Higgs doublet. The phenomenological properties of these models are emphasized, and possible cosmological implications as well as collider signatures are described.

We extend the Rome-Southampton regularization independent momentum-subtraction renormalization scheme (RI/MOM) for bilinear operators to one with a nonexceptional, symmetric subtraction point. Two-point Green’s functions with the insertion of quark bilinear operators are computed with scalar, pseudoscalar, vector, axial-vector and tensor operators at one-loop order in perturbative QCD. We call this new scheme RI/SMOM, where the S stands for “symmetric.” Conversion factors are derived, which connect the RI/SMOM scheme and the $\overline{\mathrm{MS}}$ scheme and can be used to convert results obtained in lattice calculations into the $\overline{\mathrm{MS}}$ scheme. Such a symmetric subtraction point involves nonexceptional momenta implying a lattice calculation with substantially suppressed contamination from infrared effects. Further, we find that the size of the one-loop corrections for these infrared improved kinematics is substantially decreased in the case of the pseudoscalar and scalar operator, suggesting a much better behaved perturbative series. Therefore it should allow us to reduce the error in the determination of the quark mass appreciably.

We consider corrections to nucleon correlation functions arising from times that are far from the asymptotic limit. For such times, the single-nucleon state is contaminated by the pion-nucleon and pion-delta continuum. We use heavy baryon chiral perturbation theory to derive the spectral representation of the nucleon two-point function. Finite-time corrections to the axial-current correlation function are also derived. Pion-nucleon excited-state contributions drive the axial correlator upward, while contributions from the interference of pion-delta and pion-nucleon states drive the axial correlator downward. Our results can be compared qualitatively to optimized nucleon correlators calculated in lattice QCD, because the chiral corrections characterize only low-energy excitations above the ground state. While our computations suggest that the nucleon axial charge is subject to overestimation, we speculate as to how underestimation might arise from the use of highly improved nucleon operators.

The inclusive light hadronic decays of ${}^{1}D_2$ heavy quarkonia are studied within the framework of the nonrelativistic QCD at the leading order in $v$ and up to the order of ${\alpha }_s^3$. With one-loop QCD corrections, the infrared divergences and Coulomb singularities in the decay amplitudes are proved to be absorbed by the renormalization of the matrix elements of corresponding nonrelativistic QCD operators, and the infrared finite short-distance coefficients are obtained through the matching calculations. By taking the factorization scale to be $2m_Q$, the light hadronic decay widths are estimated to be about 274, 4.7, and 8.8 KeV for ${\eta }_{c2}$, ${\eta }_{b2}$, and ${\eta }_{b2}^{\prime }$, respectively. Based on the above estimates, and using the E1 transition width and dipion transition width for ${\eta }_{c2}$ estimated elsewhere, we get the total width of ${\eta }_{c2}$ to be about 660–810 KeV, and the branching ratio of the E1 transition ${\eta }_{c2}\to \gamma h_c$ to be about (44–54)%, which will be useful in searching for this missing charmonium state through, e.g., ${\eta }_{c2}\to \gamma h_c$ followed by $h_c\to \gamma {\eta }_c$.

We assess the model discriminating power of a combined phenomenological analysis of $\mu \to e\gamma$ and $\mu \to e$ conversion on different target nuclei, including the current hadronic uncertainties. We find that the theoretical uncertainties can be largely reduced by using input from lattice QCD, and do not constitute a limiting factor in discriminating models where one or, at most, two underlying operators (dipole, scalar, vector) provide the dominant source of lepton flavor violation. Our results show that a realistic discrimination among underlying mechanisms requires a measurement of the ratio of conversion rates at the 5% level (two light nuclei) or at the 20% level (one light and one heavy nucleus). We also illustrate these main conclusions in the context of a supersymmetric model.

The Christodoulou memory is a nonlinear contribution to the gravitational-wave field that is sourced by the gravitational-wave stress-energy tensor. For quasicircular, inspiralling binaries, the Christodoulou memory produces a growing, nonoscillatory change in the gravitational-wave “plus” polarization, resulting in the permanent displacement of a pair of freely-falling test masses after the wave has passed. In addition to its nonoscillatory behavior, the Christodoulou memory is interesting because even though it originates from 2.5 post-Newtonian (PN) order multipole interactions, it affects the waveform at leading (Newtonian/quadrupole) order. The memory is also potentially detectable in binary black-hole mergers. While the oscillatory pieces of the gravitational-wave polarizations for quasicircular, inspiralling compact binaries have been computed to 3PN order, the memory contribution to the polarizations has only been calculated to leading order (the next-to-leading order 0.5PN term has previously been shown to vanish). Here the calculation of the memory for quasicircular, inspiralling binaries is extended to 3PN order. While the angular dependence of the memory remains qualitatively unchanged, the PN correction terms tend to reduce the memory’s magnitude. Explicit expressions are given for the memory contributions to the plus polarization and the spin-weighted spherical-harmonic modes of the metric and curvature perturbations. Combined with the recent results of Blanchet et al. [Classical Quantum Gravity 25, 165003 (2008)], this completes the waveform polarizations to 3PN order. This paper also discusses: (i) the difficulties in extracting the memory from numerical relativity simulations, (ii) other nonoscillatory effects that enter the waveform polarizations at high PN orders, and (iii) issues concerning the observability of the memory in gravitational-wave detectors.

In considering the gravitational collapse of matter, it is an important problem to clarify what kind of conditions leads to the formation of naked singularity. For this purpose, we apply the $1+3$ orthonormal frame formalism introduced by Uggla et al. to the spherically symmetric gravitational collapse of a perfect fluid. This formalism allows us to construct an autonomous system of evolution and constraint equations for scale-invariant dynamical variables normalized by the volume expansion rate of the timelike orthonormal frame vector. We investigate the asymptotic evolution of such dynamical variables towards the formation of a central singularity and present a conjecture that the steep spatial gradient for the normalized density function is a characteristic of the naked singularity formation.

Arguably a major success of the landscape picture is the prediction of a small, nonzero vacuum energy density. The details of this prediction depend in part on how the diverging spacetime volume of the multiverse is regulated, a question that remains unresolved. One proposal, the causal diamond measure, has demonstrated many phenomenological successes, including predicting a distribution of positive vacuum energy densities in good agreement with observation. In the string landscape, however, the vacuum energy density is expected to take positive and negative values. We find the causal diamond measure gives a poor fit to observation in such a landscape—in particular, 99.6% of observers in galaxies seemingly just like ours measure a vacuum energy density smaller than we do, most of them measuring it to be negative.

We provide a novel mechanism that resolves the big bang singularity present in Friedman-Lemaitre-Robertson-Walker space-times without the need for ghost fields. Building on the fact that a four-fermion interaction arises in general relativity when fermions are covariantly coupled, we show that at early times the decrease in scale factor enhances the correlation between pairs of fermions. This enhancement leads to a BCS-like condensation of the fermions and opens a gap dynamically driving the Hubble parameter $H$ to zero and results in a nonsingular bounce, at least in some special cases.

We present a simple variation of warped flavor models where the hierarchies of fermion masses and mixings are still explained but dangerous flavor-violating effects in the Kaon sector are greatly reduced. The key new ingredients are two horizontal $U(1)$ symmetries. These symmetries forbid flavor violation in the down-quark sector (with the exception of IR brane localized kinetic mixing terms for the left-handed quarks) while allowing for flavor violation in the up-quark sector. The leading flavor constraints come from $D^0-{\overline{D}}^0$ mixing, and are safely satisfied for the Kaluza-Klein mass scale of order 3 TeV. Our analysis of the flavor constraints includes the effects of the (usually ignored) brane localized kinetic terms. We also comment on the effects of the additional $U(1)$ gauge bosons that are present if the horizontal symmetries are gauged.

The next generation of gravitational wave (gw) detectors is expected to fully enter into the quantum regime of force and displacement detection. With this aim, it is important to scale up the experiments on opto-mechanical effects from the microscopic regime to large mass systems and test the schemes that should be applied to reach the quantum regime of detection. In this work we present the experimental characterization of a prototype of massive gw detector, composed of two oscillators with a mass of the order of the kg, whose distance is read by a high finesse optical cavity. The mechanical response function is measured by exciting the oscillators through modulated radiation pressure. We demonstrate two effects crucial for the next generation of massive, cryogenic gw detectors (DUAL detectors): (a) the reduction of the contribution of ’local’ susceptibility thanks to an average over a large interrogation area. Such effect is measured on the photo-thermal response thanks to the first implementation of a folded-Fabry-Perot cavity; (b) the ’backaction reduction’ due to negative interference between acoustic modes. Moreover, we obtain the active cooling of an oscillation mode through radiation pressure, on the described mechanical device which is several orders of magnitude heavier than previously demonstrated radiation-pressure cooled systems.

In $\mathrm{SU}(N)$ gauge theories with fermions in the fundamental or in a two-index (either symmetric or antisymmetric) representation formulated on a manifold with at least one compact dimension with nontrivial holonomy the discrete symmetries $C$, $P$, and $T$ are broken at small enough size of the compact direction(s) for certain values of $N$. We show that for those $N$ in the broken phase a nonzero baryon current wrapping in the compact direction exists, which provides a measurable observable for the breaking of $C$, $P$, and $T$. We prove that in all cases where the current is absent there is no breaking of those discrete symmetries. This includes the limit $N\to \infty$ of the $\mathrm{SU}(N)$ gauge theory with symmetric or antisymmetric fermions and $\mathrm{U}(N)$ gauge theory at any value of $N$. We then argue that the component of the baryon current in the compact direction is the physical order parameter for $C$, $P$, and $T$ breaking due to the breaking of Lorentz invariance.