The HyperCP collaboration has recently reported the observation of three events for the decay ${\Sigma }^{+}\to p{\mu }^{+}{\mu }^{-}$. They have suggested that new physics may be required to understand the implied decay rate and the observed $M_{\mu \mu }$ distribution. Motivated by this result, we reexamine this mode within the standard model, considering both the short-distance and long-distance contributions. The long-distance part depends on four complex form factors. We determine their imaginary parts from unitarity, fix two of the real parts from the ${\Sigma }^{+}\to p\gamma$ measurements, and estimate the other two with vector-meson-dominance models. Taking into account constraints from ${\Sigma }^{+}\to p{e}^{+}{e}^{-}$, we find that ${\Sigma }^{+}\to p{\mu }^{+}{\mu }^{-}$ is long-distance dominated and its rate falls within the range suggested by the HyperCP measurement.

The branching fraction of the ${\tau }^{-}\to 3h^{-}2h^{+}{\nu }_{\tau }$ decay ($h=\pi ,K$) is measured with the BABAR detector to be $(8.56\pm 0.05\pm 0.42)\times {10}^{-4}$, where the first error is statistical and the second systematic. The observed structure of this decay is significantly different from the phase space prediction, with the $\rho$ resonance playing a strong role. The decay ${\tau }^{-}\to f_1(1285){\pi }^{-}{\nu }_{\tau }$, with the $f_1(1285)$ meson decaying to four charged pions, is observed and the branching fraction is measured to be $(3.9\pm 0.7\pm 0.5)\times {10}^{-4}$.

The $O(\alpha )$ QED and electroweak radiative corrections to neutrino-deuteron reactions is investigated with particular emphasis given to the constant terms, which have not been treated properly in the literature. This problem is related to the definition of the axial-vector coupling constant $g_A$ as to the inclusion of radiative corrections. After proper calculations of the constants for the Fermi and Gamow-Teller transitions, we find the radiative correction to the neutral current induced reaction, with the usually adopted definition of $g_A$, is 1.017 for the Higgs boson mass $m_H=1.5m_Z$. This value is close to that given by Kurylov et al., but this is due to an accidental cancellation of the errors, between those caused by putative identification of constant terms for the Fermi and Gamow-Teller transitions for the charged current reactions and minor errors in their treatment of the constant terms for the neutral current induced reactions.

We present a parameter-free gauge formulation of general relativity in terms of a new set of real spin connection variables. The theory is constructed by extending the phase space of the recently formulated conformal geometrodynamics to accommodate a spin-gauge description. This leads to a further enlarged set of first class gravitational constraints consisting of a reduced Hamiltonian constraint and the canonical generators for spin-gauge and conformorphism transformations. Owing to the incorporated conformal symmetry, the new theory is shown to be free from an ambiguity of the Barbero-Immirzi type.

Using the mixed space representation $(t,\overrightarrow{p})$ in the context of scalar field theories, we prove in a simple manner that the Feynman graphs at finite temperature are related to the corresponding zero temperature diagrams through a simple thermal operator, both in the imaginary time as well as in the real time formalisms. This result is generalized to the case when there is a nontrivial chemical potential present. Several interesting properties of the thermal operator are also discussed.

We investigate the feasibility that, in the field of a superstrong standing laser wave, high-order harmonics of the pumping laser are generated from vacuum. Analytical calculations employing adiabatic perturbation theory show that, for laser electric fields larger than $E_{\mathrm{cr}}=m^2{c}^3/\hslash e=1.3\times {10}^{16}\mathrm{V}/\mathrm{cm}$, high-order harmonics are generated. The harmonic spectrum shows a wide plateau followed by a cutoff. The cutoff starts approximately at photon energies $\hslash {\omega }_M\sim \sqrt{\hslash ec{E}_L}$, with $E_L$ being the amplitude of the laser field. In the opposite limit $E_L\ll E_{\mathrm{cr}}$, the emission of high harmonics is very unlikely. In this case, a feasibility analysis for the experimental observation of the photon-photon scattering process using x-ray free electron lasers shows that the requirements are much less restrictive than those required to observe electron-positron pair creation.

Webs of domain walls are constructed as $1/4$ Bogomol’nyi-Prasad-Sommerfield (BPS) states in $d=4$, $\mathcal{N}=2$ supersymmetric $\mathrm{U}(N_{\mathrm{C}})$ gauge theories with $N_{\mathrm{F}}$ hypermultiplets in the fundamental representation. Webs of walls can contain any numbers of external legs and loops like $(p,q)$ string/5-brane webs. We find the moduli space $\mathcal{M}$ of a $1/4$ BPS equation for wall webs to be the complex Grassmann manifold. When moduli spaces of $1/2$ BPS states (parallel walls) and the vacua are removed from $\mathcal{M}$, the noncompact moduli space of genuine $1/4$ BPS wall webs is obtained. All the solutions are obtained explicitly and exactly in the strong gauge coupling limit. In the case of Abelian gauge theory, we work out the correspondence between configurations of wall web and the moduli space $\mathbf{C}{P}^{N_{\mathrm{F}}-1}$.

We discuss certain general features of type B warped spacetimes which have important consequences on the material content they may admit and its associated dynamics. We show that, for warped B spacetimes, if shear and anisotropy are nonvanishing, they have to be proportional. We also study some of the physics related to the warping factor and of the underlying decomposable metric. Finally we explore the only possible cases compatible with a type B warped geometry which satisfy the dominant energy conditions. As an example of the above mentioned consequences we consider a radiating fluid and two nonspherically symmetric metrics which depend upon an arbitrary parameter $a$, such that for $a=0$ spherical symmetry is recovered.

We construct physical semiclassical states annihilated by the Hamiltonian constraint operator in the framework of loop quantum cosmology as a method of systematically determining the regime and validity of the semiclassical limit of the quantum theory. Our results indicate that the evolution can be effectively described using continuous classical equations of motion with nonperturbative corrections down to near the Planck scale below which the Universe can only be described by the discrete quantum constraint. These results, for the first time, provide concrete evidence of the emergence of classicality in loop quantum cosmology and also clearly demarcate the domain of validity of different effective theories. We prove the validity of modified Friedmann dynamics incorporating discrete quantum geometry effects which can lead to various new phenomenological applications. Furthermore the understanding of semiclassical states allows for a framework for interpreting the quantum wave functions and understanding questions of a semiclassical nature within the quantum theory of loop quantum cosmology.

A theorem providing a characterization of Schwarzschildean initial data sets on slices with an asymptotically Euclidean end is proved. This characterization is based on the proportionality of the Weyl tensor and its D’Alambertian that holds for some vacuum Petrov type D spacetimes (e.g. the Schwarzschild spacetime, the C-metric, but not the Kerr solution). The $3+1$ decomposition of this proportionality condition renders necessary conditions for an initial data set to be a Schwarzschildean initial set. These conditions can be written as quadratic expressions of the electric and magnetic parts of the Weyl tensor, and thus involve only the freely specifiable data. In order to complete our characterization, a study of which vacuum static Petrov type D spacetimes admit asymptotically Euclidean slices is undertaken. Furthermore, a discussion of the Arnowitt-Deser-Misner (ADM) 4-momentum for boost-rotation symmetric spacetimes is given. As a by-product of our analysis a certain characterization of the Schwarzschild spacetime is obtained. Finally, a generalization of our characterization, valid for Schwarzschildean hyperboloidal initial data sets is put forward.

Inflation may have been driven by a component which violated the Null-Energy Condition, thereby leading to super inflation. We provide the formalism to study cosmological perturbations when such a component is described by a scalar field with arbitrary Lagrangian. Since the background curvature grows with time, gravitational waves always have a blue spectrum. We apply our formalism to the case of phantom inflation with an exponential potential (whose polelike inflationary stage is an attractor for inhomogeneous cosmological models for any value of the potential slope) as an example. We finally compare the predictions of super inflation with those of standard inflation stressing the role of gravitational waves.

We revisit the constraints imposed by electric dipole moments (EDMs) of nucleons and heavy atoms on new $CP$-violating sources within supersymmetric theories. We point out that certain two-loop renormalization group corrections induce significant mixing between the basis-invariant $CP$-odd phases. In the framework of the constrained minimal supersymmetric standard model, the $CP$-odd invariant related to the soft trilinear $A$-phase at the grand unified theory (GUT) scale, ${\theta }_A$, induces nontrivial and distinct $CP$-odd phases for the three gaugino masses at the weak scale. The latter give one-loop contributions to EDMs enhanced by $\tan \beta$, and can provide the dominant contribution to the electron EDM induced by ${\theta }_A$. We perform a detailed analysis of the EDM constraints within the constrained minimal supersymmetric standard model, exhibiting the reach, in terms of sparticle spectra, which may be obtained assuming generic phases, as well as the limits on the $CP$-odd phases for some specific parameter points where detailed phenomenological studies are available. We also illustrate how this reach will expand with results from the next generation of experiments which are currently in development.

We calculate the Debye and Meissner masses and investigate chromomagnetic instability associated with the gapless color superconducting phase changing the strange quark mass $M_s$ and the temperature $T$. Based on the analytical study, we develop a computational procedure to derive the screening masses numerically from curvatures of the thermodynamic potential. When the temperature is zero, from our numerical results for the Meissner masses, we find that instability occurs for $A_1$ and $A_2$ gluons entirely in the gapless color-flavor locked (gCFL) phase, while the Meissner masses are real for $A_4$, $A_5$, $A_6$, and $A_7$ until $M_s$ exceeds a certain value that is larger than the gCFL onset. We then handle mixing between color-diagonal gluons $A_3$, $A_8$, and photon $A_{\gamma }$, and clarify that, among three eigenvalues of the mass squared matrix, one remains positive, one is always zero because of an unbroken $\mathrm{U}(1{)}_{\tilde{Q}}$ symmetry, and one exhibits chromomagnetic instability in the gCFL region. We also examine the temperature effects that bring modifications into the Meissner masses. The instability found at large $M_s$ for $A_4$, $A_5$, $A_6$, and $A_7$ persists at finite $T$ into the $u$-quark color superconducting (uSC) phase which has $u$-$d$ and $s$-$u$ but no $d$-$s$ quark pairing and also into the two-flavor color superconducting (2SC) phase characterized by $u$-$d$ quark pairing only. The $A_1$ and $A_2$ instability also goes into the uSC phase, but the 2SC phase has no instability for $A_1$, $A_2$, and $A_3$. We map the unstable region for each gluon onto the phase diagram as a function of $M_s$ and $T$.

In their recent paper, Kosowsky et al. commented about our earlier work in which we derived very stringent limits on the amplitude of a primordial magnetic field from gravitational wave production. They argue that our limits are erroneous. In this short Comment we defend our result.

We consider the radiation emitted by an ultrarelativistic charged particle moving in a magnetic field, in the presence of an additional Lorentz-violating interaction. In contrast with prior work, we treat a form of Lorentz violation that is represented by a renormalizable operator. Neglecting the radiative reaction force, the particle’s trajectory can be determined exactly. The resulting orbit is generally noncircular and does not lie in the plane perpendicular to the magnetic field. We do not consider any Lorentz violation in the electromagnetic sector, so the radiation from the accelerated charge can be determined by standard means, and the radiation spectrum will exhibit a Lorentz-violating directional dependence. Using data on emission from the Crab nebula, we can set a bound on a particular combination of Lorentz-violating coefficients at the $6\times {10}^{-20}$ level.

The asymptotic scheme of post-Newtonian approximation defined for general relativity in the harmonic gauge by Futamase & Schutz (1983) is based on a family of initial data for the matter fields of a perfect fluid and for the initial metric, defining a family of weakly self-gravitating systems. We show that Weinberg’s (1972) expansion of the metric and his general expansion of the energy-momentum tensor $\mathbf{T}$, as well as his expanded equations for the gravitational field and his general form of the expanded dynamical equations, apply naturally to this family. Then, following the asymptotic scheme, we derive the explicit form of the expansion of $\mathbf{T}$ for a perfect fluid, and the expanded fluid-dynamical equations. (These differ from those written by Weinberg.) By integrating these equations in the domain occupied by a body, we obtain a general form of the translational equations of motion for a 1PN perfect-fluid system in general relativity. To put them into a tractable form, we use an asymptotic framework for the separation parameter $\eta$, by defining a family of well-separated 1PN systems. We calculate all terms in the equations of motion up to the order ${\eta }^3$ included. To calculate the 1PN correction part, we assume that the Newtonian motion of each body is a rigid one, and that the family is quasispherical, in the sense that in all bodies the inertia tensor comes close to being spherical as $\eta \to 0$. Apart from corrections that cancel for exact spherical symmetry, there is in the final equations of motion one additional term, as compared with the Lorentz-Droste (Einstein-Infeld-Hoffmann) acceleration. This term depends on the spin of the body and on its internal structure.

We study the impact of the halo shape and geometry on the expected weakly interacting massive particle (WIMP) dark matter annihilation signal from the galactic center. As the halo profile in the innermost region is still poorly constrained, we focus on geometrical distortions and consider different density behaviors like flat cores, cusps, and spikes. We show that asphericity has a strong impact on the annihilation signal when the halo profile near the galactic center is flat, but becomes gradually less significant for cuspy profiles, and negligible in the presence of a central spike. However, the astrophysical factor is strongly dependent on the weakly interacting massive particle mass and annihilation cross section in the latter case.

We consider the cross section limits for light dark matter cadnidates ($m=0.4$ to 10 GeV). We calculate the interaction of dark matter in the crust above underground dark matter detectors and find that in the intermediate cross section range, the energy loss of dark matter is sufficient to fall below the energy threshold of current underground experiments. This implies the existence of a window in the dark matter exclusion limits in the micro-barn range.

Weak gravitational lensing of background galaxies offers an excellent opportunity to study the intervening distribution of matter. While much attention to date has focused on the two-point-function of the cosmic shear, the three-point-function, the bispectrum, also contains very useful cosmological information. Here, we compute three corrections to the bispectrum which are nominally of the same order as the leading term. We show that the corrections are small, so they can be ignored when analyzing present surveys. However, they will eventually have to be included for accurate parameter estimates from future surveys.

This paper presents a first study of the masses and decay constants of the charged, or flavor-off-diagonal, pseudoscalar mesons to two loops for two flavors of sea-quarks, in Partially Quenched Chiral Perturbation Theory ($\mathrm{PQ}\chi \mathrm{PT}$). Explicit analytical expressions up to $\mathcal{O}(p^6)$ in the momentum expansion are given. The calculations have been performed within the supersymmetric formulation of $\mathrm{PQ}\chi \mathrm{PT}$. A numerical analysis is done to indicate the size of the corrections.