The values of the presently available truncated perturbative expressions for the pressure of the quark-gluon plasma at finite temperatures and finite chemical potential are trustworthy only at very large energies. When used down to temperatures close to the critical one ($T_c$), they suffer from large uncertainties due to the renormalization scale freedom. In order to reduce these uncertainties, we perform resummations of the pressure by applying two specific Padé-related approximants to the available perturbation series for the short-distance and for the long-distance contributions. In the two contributions, we use two different renormalization scales which reflect different energy regions contributing to the different parts. Application of the obtained expressions at low temperatures is made possible by replacing the usual four-loop $\overline{\mathrm{MS}}$ beta function for ${\alpha }_s$ by its Borel-Padé resummation, thus eliminating the unphysical Landau singularities of ${\alpha }_s$. The obtained results are remarkably insensitive to the chosen renormalization scale and can be compared with lattice results—for the pressure $p$, the chemical potential contribution $\Delta p$ to the pressure, and various susceptibilities. A good qualitative agreement with the lattice results is revealed down to temperatures close to $T_c$.

The production of a $W$ boson and two jets, at least one of which contains a $b$ quark, is a principal background to single-top production, Higgs production, and signals of new physics at hadron colliders. We present a next-to-leading-order calculation of the cross section at the Fermilab Tevatron and the CERN Large Hadron Collider. The next-to-leading-order cross section differs substantially from that at leading order, and we provide a context in which to understand this result.

We estimate the coupling of the $K^{*}$ vector meson to the $N\to {\Theta }^{+}$ transition employing unitary symmetry, vector-meson dominance, and results from the GRAAL Collaboration for $\eta$ photoproduction off the neutron. Our small numerical value for the coupling constant is consistent with the nonobservation of the ${\Theta }^{+}$ in recent CLAS searches for its photoproduction. We also estimate the $K^{*}$-coupling for the $N\to {\Sigma }^{*}$ excitation, with ${\Sigma }^{*}$ being the $\Sigma$-like antidecuplet partner of the ${\Theta }^{+}$-baryon.

New sum rules for $B\to \pi ,K$ and $B\to \rho ,K^{*}$ form factors are derived from the correlation functions expanded near the light cone in terms of $B$-meson distribution amplitudes. The contributions of quark-antiquark and quark-antiquark-gluon components in the $B$ meson are taken into account. Models for the $B$-meson three-particle distribution amplitudes are suggested, based on QCD sum rules in heavy-quark effective theory. Employing the new light-cone sum rules, we calculate the form factors at small momentum transfers, including $SU(3)$-violation effects. The results agree with the predictions of the conventional light-cone sum rules.

We search for the decays $B^{-}\to \varphi K^{-}\gamma$ and ${\overline{B}}^0\to \varphi {\overline{K}}^0\gamma$ in a data sample of $228\times {10}^6$ $B\overline{B}$ pairs collected at the $\mathit{{\rm Y}}(4S)$ resonance with the BABAR detector. We measure the branching fraction $\mathcal{B}(B^{-}\to \varphi K^{-}\gamma )=(3.5\pm 0.6\pm 0.4)\times {10}^{-6}$ and set an upper limit $\mathcal{B}({\overline{B}}^0\to \varphi {\overline{K}}^0\gamma )<2.7\times {10}^{-6}$ at the 90% confidence level. We also measure the direct $CP$ asymmetry in $B^{-}\to \varphi K^{-}\gamma$, ${\mathcal{A}}_{CP}=(-26\pm 14\pm 5)\%$. The uncertainties are statistical and systematic, respectively.

The “moving-puncture” technique has led to dramatic advancements in the numerical simulations of binary black holes. Hannam et al. have recently demonstrated that, for suitable gauge conditions commonly employed in moving-puncture simulations, the evolution of a single black hole leads to a well-known, time-independent, maximal slicing of Schwarzschild spacetime. They construct the corresponding solution in isotropic coordinates numerically and demonstrate its usefulness, for example, for testing and calibrating numerical codes that employ moving-puncture techniques. In this brief report we point out that this solution can also be constructed analytically, making it even more useful as a test case for numerical codes.

We compute the one-loop gauge couplings in six-dimensional non-Abelian gauge theories on the $T^2/Z_2$ orbifold with general GUT breaking boundary conditions. For concreteness, we apply the obtained general formulas to the gauge coupling running in a 6D $SO(10)$ orbifold GUT where the GUT group is broken down to the standard model gauge group up to an extra $U(1)$. We find that the one-loop corrections depend on the parity matrices encoding the orbifold boundary conditions as well as the volume and shape moduli of extra dimensions. When the $U(1)$ is broken by the VEV of bulk singlets, the accompanying extra color triplets also affect the unification of the gauge couplings. In this case, the $B-L$ breaking scale compatible with the gauge coupling unification is sensitive to the change of the compactification scales.

Coupling constants at high energy scales are studied in SU(N) gauge theory with distinct sizes of extra dimensions. We present the solution of gauge couplings as functions of the energy in such a way as to track the number of Kaluza-Klein modes. In a flat extra dimension, it is shown that the gauge couplings have logarithmic dependence on the size of the extra dimension and linear dependence on the number of Kaluza-Klein modes. We find some patterns of the dependence on flavor of bulk and brane fermions. Dependence of gauge couplings on the size of an extra dimension is discussed also in a warped extra dimension.

From information theory and thermodynamic considerations a universal bound on the relaxation time $\tau$ of a perturbed system is inferred, $\tau \ge \hslash /\pi T$, where $T$ is the system’s temperature. We show that black holes comply with the bound; in fact they may actually saturate it. Thus, when judged by their relaxation properties, black holes are the most extreme objects in nature, having the maximum relaxation rate which is allowed by quantum theory.

The evolution equations for tensor perturbations in a generic scalar-tensor theory of gravity are presented. Exact solutions are given for a specific class of theories and Friedmann-Lemaître-Robertson-Walker backgrounds. In these cases it is shown that, although the evolution of tensor models depends on the choice of parameters of the theory, no amplification is possible if the gravitational interaction is attractive.

We study the prospects for constraining dark energy at very high redshift with the Sandage-Loeb test—a measurement of the evolution of cosmic redshift obtained by taking quasar spectra at sufficiently separated epochs. This test is unique in its coverage of the “redshift desert,” corresponding roughly to redshifts between 2 and 5, where other dark energy probes are unable to provide useful information about the cosmic expansion history. Extremely large telescopes planned for construction in the near future, with ultrahigh resolution spectrographs (such as the proposed CODEX), will indeed be able to measure cosmic redshift variations of quasar Lyman-$\alpha$ absorption lines over a period as short as ten years. We find that these measurements can constrain nonstandard and dynamical dark energy models with high significance and in a redshift range not accessible with future dark energy surveys. As the cosmic signal increases linearly with time, measurements made over several decades by a generation of patient cosmologists may provide definitive constraints on the expansion history in the era that follows the dark ages but precedes the time when standard candles and rulers come into existence.

We show that an isotropic component of circular polarization of a stochastic gravitational wave background can be explored by contriving configuration of multiple laser interferometers for correlation analysis. For the proposed BBO mission, the circular polarization degree $\Pi$ can be measured down to $\Pi \sim 0.08({\Omega }_{\mathrm{GW}}/{10}^{-15}{)}^{-1}(\mathrm{SNR}/5)$ with slightly ($\sim 10\%$) sacrificing the detection limit for the total intensity ${\Omega }_{\mathrm{GW}}$. This might allow us to detect a signature of parity violation in the very early universe.

We study a Lorentz invariance violating extension for the pure photonic sector of the standard model. A phenomenological proposal is made for the condensation of topological defects in the presence of a constant rank-$m$ tensor in the context of the Julia-Toulouse mechanism. Possible physical consequences leading to direct measurable effects over the confining properties of the elementary particles are explored.

Electromagnetic resonant cavities form the basis for a number modern tests of Lorentz invariance. The geometry of most of these experiments implies unsuppressed sensitivities to parity-even Lorentz violations only. Parity-odd violations typically enter through suppressed boost effects, causing a reduction in sensitivity by roughly 4 orders of magnitude. Here we discuss possible techniques for achieving unsuppressed sensitivities to parity-odd violations using asymmetric resonators.

We study the stability of the kaon condensed color-flavor locked (CFL) phase of dense quark matter with regard to the formation of a nonzero Goldstone boson current. In the kaon condensed phase there is an electrically charged fermion which becomes gapless near ${\mu }_s^{(1)}\simeq 1.35\Delta$ and a neutral fermion which becomes gapless near ${\mu }_s^{(2)}\simeq 1.61\Delta$. Here, ${\mu }_s=m_s^2/(2p_F)$ is the shift in the Fermi energy due to the strange quark mass $m_s$ and $\Delta$ is the gap in the chiral limit. The transition to the gapless phase is continuous at ${\mu }_s^{(1)}$ and first order at ${\mu }_s^{(2)}$. We find that the magnetic screening masses are real in the regime ${\mu }_s<{\mu }_s^{(2)}$, but some screening masses are imaginary for ${\mu }_s>{\mu }_s^{(2)}$. We show that there is a very weak current instability for ${\mu }_s>{\mu }_s^{(1)}$ and a more robust instability in a small window near ${\mu }_s^{(2)}$. We show that in the Goldstone boson current phase all components of the magnetic screening mass are real. There is a range of values of ${\mu }_s$ below $2\Delta$ in which the magnetic gluon screening masses are imaginary but the phase is stable with respect to electrically neutral fluctuations of the gauge field.

We demonstrate how to resum phase space logarithms in the Sterman-Weinberg (SW) dijet decay rate within the context of soft collinear effective theory (SCET). An operator basis corresponding to two and three jet events is defined in SCET and renormalized. We obtain the renormalization group equation of the two and three jet operators and run the operators from the scale ${\mu }^2=Q^2$ to the phase space scale ${\mu }_{\delta }^2={\delta }^2{Q}^2$. This phase space scale, where $\delta$ is the cone half angle of the jet, defines the angular region of the jet. At ${\mu }_{\delta }^2$ we determine the mixing of the three and two jet operators. We combine these results with the running of the two jet shape function, which we run down to an energy cut scale ${\mu }_{\beta }^2$. This defines the resummed SW dijet decay rate in the context of SCET. The approach outlined here demonstrates how to establish a jet definition in the context of SCET. This allows a program of systematically improving the theoretical precision of jet phenomenology to be carried out.

As the annihilation contributions play important roles in solving the puzzle of the small longitudinal polarizations in $B\to K^{*}\varphi$ decays, we examine similar effects in the decays of $B\to K_{0,2}^{*}(1430)\varphi$. For the calculations on the annihilated contributions, we adopt that the form factors in $B\to K^{(*)}\varphi$ decays are parameters determined by the observed branching ratios (BRs), polarization fractions, and relative angles in experiments, and we connect the parameters between $B\to K_{0(2)}^{*}\varphi$ and $B\to K^{(*)}\varphi$. We find that the BR of $B_d\to K_0^{*0}(1430)\varphi$ is $(3.69\pm 0.47)\times {10}^{-6}$. We show that the BR of $B_d\to K_2^{*0}(1430)\varphi$ is $(1.70\pm 0.80)\times {10}^{-6}$ in the 2nd version of the Isgur-Scora-Grinstein-Wise (ISGW2) model, whereas it can be a broad range of values in the light-front quark model. In terms of the recent BABAR observations on BRs and polarization fractions in $B_d\to K_2^{*0}(1430)\varphi$, the results in the light-front quark model are found to be more favorable. In addition, due to the annihilation contributions to $B\to K_2^{*}\varphi$ and $B\to K^{*}\varphi$ being opposite in sign, we demonstrate that the longitudinal polarization of $B_d\to K_2^{*0}(1430)\varphi$ is always $O(1)$ with or without including the annihilation contributions.

We study the stability of the Harrison-Perkins-Scott (HPS) mixing pattern, assumed to hold at some high energy scale, against supersymmetric radiative corrections. We work in the framework of a reference minimal supergravity model (mSUGRA) where supersymmetry breaking is universal and flavor-blind at unification. The radiative corrections considered include both RGE running as well as threshold effects. We find that in this case the solar mixing angle can only increase with respect to the HPS reference value, while the atmospheric and reactor mixing angles remain essentially stable. Deviations from the solar angle HPS prediction towards lower values would signal novel contributions from physics beyond the simplest mSUGRA model.

We report on a high statistics measurement of the cross section of the process $\gamma \gamma \to {\pi }^{+}{\pi }^{-}$ in the ${\pi }^{+}{\pi }^{-}$ invariant mass range $0.8\mathrm{GeV}/c^2<W<1.5\mathrm{GeV}/c^2$ with $85.9{\mathrm{fb}}^{-1}$ of data collected at $\sqrt{s}=10.58\mathrm{GeV}$ and 10.52 GeV with the Belle detector. A clear signal for the $f_0(980)$ resonance is observed. From a fit to the mass spectrum, the mass, ${\pi }^{+}{\pi }^{-}$ and two-photon decay widths of the resonance are found to be ${985.6}_{-1.5}^{+1.2}(\mathrm{stat}{)}_{-1.6}^{+1.1}(\mathrm{syst})\mathrm{MeV}/c^2$, ${34.2}_{-11.8}^{+13.9}(\mathrm{stat}{)}_{-2.5}^{+8.8}(\mathrm{syst})\mathrm{MeV}$, and ${205}_{-83}^{+95}(\mathrm{stat}{)}_{-117}^{+147}(\mathrm{syst})\mathrm{eV}$, respectively.