The best natural candidates for the realization of color superconductivity are quark stars—not yet confirmed by observation—and the extremely dense cores of compact stars, many of which have very large magnetic fields. To reliably predict astrophysical signatures of color superconductivity, a better understanding of the role of the star’s magnetic field in the color-superconducting phase that is realized in the core is required. This paper is an initial step in that direction. The field scales at which the different magnetic phases of a color superconductor with three quark flavors can be realized are investigated. Going from weak to strong fields, the system first undergoes a symmetry transmutation from a color-flavor-locked (CFL) phase to a magnetic-CFL (MCFL) phase, and then a phase transition from the MCFL phase to the paramagnetic-CFL (PCFL) phase. The low-energy effective theory for the excitations of the diquark condensate in the presence of a magnetic field is derived using a covariant representation that takes into account all the Lorentz structures contributing at low energy. The field-induced masses of the charged mesons and the threshold field at which the $\mathrm{CFL}\to \mathrm{MCFL}$ symmetry transmutation occurs are obtained in the framework of this low-energy effective theory. The relevance of the different magnetic phases for the physics of compact stars is discussed.

We present a new technique for time-domain numerical evolution of the scalar- field generated by a pointlike scalar charge orbiting a black hole. Time-domain evolution offers an efficient way for calculating black hole perturbations, especially as input for computations of the local self force acting on orbiting particles. In Kerr geometry, the field equations are not fully separable in the time domain, and one has to tackle them in $2+1$ dimensions (two spatial dimensions and time; the azimuthal dependence is still separable). A technical difficulty arises when the source of the field is a pointlike particle, as the $2+1$-dimensional perturbation is then singular: Each of the azimuthal modes diverges logarithmically at the particle. To deal with this problem we split the numerical domain into two regions: Inside a thin worldtube surrounding the particle’s worldline we solve for a regularized variable, obtained from the full field by subtracting out a suitable puncture function, given analytically. Outside this worldtube we solve for the full, original field. The value of the evolution variable is adjusted across the boundary of the worldtube. In this work we demonstrate the applicability of this method in the example of circular orbits around a Schwarzschild black hole (refraining from exploiting the spherical symmetry of the background, and working in $2+1$ dimensions).

A new constraint suppressing formulation of the Einstein evolution equations is presented, generalizing the five-parameter first-order system due to Kidder, Scheel, and Teukolsky (KST). The auxiliary fields, introduced to make the KST system first order, are given modified evolution equations designed to drive constraint violations toward zero. The algebraic structure of the new system is investigated, showing that the modifications preserve the hyperbolicity of the fundamental and constraint evolution equations. The evolution of the constraints for perturbations of flat spacetime is completely analyzed, and all finite-wavelength constraint modes are shown to decay exponentially when certain adjustable parameters satisfy appropriate inequalities. Numerical simulations of a single Schwarzschild black hole are presented, demonstrating the effectiveness of the new constraint-damping modifications.

We propose a Hamiltonian formalism for a generalized Friedmann-Robertson-Walker cosmology model in the presence of both a variable equation of state parameter $w(a)$ and a variable cosmological constant $\Lambda (a)$, where $a$ is the scale factor. This Hamiltonian system, containing 1 degree of freedom and without constraint, gives Friedmann equations as the equation of motion, which describes a mechanical system with a variable mass object moving in a potential field. After an appropriate transformation of the scale factor, this system can be further simplified to an object with constant mass moving in an effective potential field. In this framework, the $\Lambda$ cold dark matter model as the current standard model of cosmology corresponds to a harmonic oscillator. We further generalize this formalism to take into account the bulk viscosity and other cases. The Hamiltonian can be quantized straightforwardly, but this is different from the approach of the Wheeler-DeWitt equation in quantum cosmology.

We set an upper limit on the mass of a supersymmetric neutralino dark matter particle using the MicrOMEGAS and DarkSUSY software packages and the most recent constraints on relic density from combined Wilkinson Microwave Anisotropy Probe and Sloan Digital Sky Survey data. We explore several different possible scenarios within the minimal supersymmetric standard model, including coannihilation with charginos and sfermions and annihilation through a massive Higgs resonance, using low-energy mass inputs. We find that no coannihilation scenario is consistent with dark matter in observed abundance with a mass greater than 2.5 TeV for a $W$-ino-type particle or 1.8 TeV for a Higgsino-type. Contrived scenarios involving Higgs resonances with finely tuned mass parameters can allow masses as high as 34 TeV. The resulting gamma-ray energy distribution is not in agreement with the recent multi-TeV gamma-ray spectrum observed by H. E. S. S. originating from the center of the Milky Way. Our results are relevant only for dark matter densities resulting from a thermal origin.

In general relativity, the energy conditions are invoked to restrict general energy-momentum tensors on physical grounds. We show that in the standard Friedmann-Lemaître–Robertson-Walker (FLRW) approach to cosmological modeling, where the energy and matter components of the cosmic fluid are unknown, the energy conditions provide model-independent bounds on the behavior of the lookback time of cosmic sources as a function of the redshift for any value of the spatial curvature. We derive and confront such bounds with a lookback time sample which is built from the age estimates of 32 galaxies lying in the interval $0.11\lesssim z\lesssim 1.84$ and by assuming the total expanding age of the Universe to be $13.7\pm 0.2\mathrm{Gyr}$, as obtained from current cosmic microwave background experiments. In agreement with previous results, we show that all energy conditions seem to have been violated at some point of the recent past of cosmic evolution.

We discuss the ratio of the angular diameter distances from the source to the lens, $D_{ds}$, and to the observer at present, $D_s$, for various dark energy models. It is well known that the difference of $D_s$s between the models is apparent and this quantity is used for the analysis of Type Ia supernovae. However we investigate the difference between the ratio of the angular diameter distances for a cosmological constant, $(D_{ds}/D_s{)}^{\Lambda }$, and that for other dark energy models, $(D_{ds}/D_s{)}^{\mathrm{other}}$, in this paper. It has been known that there is lens model degeneracy in using strong gravitational lensing. Thus, we investigate the model independent observable quantity, Einstein radius (${\theta }_E$), which is proportional to both $D_{ds}/D_s$ and velocity dispersion squared, ${\sigma }_v^2$. $D_{ds}/D_s$ values depend on the parameters of each dark energy model individually. However, $(D_{ds}/D_s{)}^{\Lambda }-(D_{ds}/D_s{)}^{\mathrm{other}}$ for the various dark energy models, is well within the error of ${\sigma }_v$ for most of the parameter spaces of the dark energy models. Thus, a single strong gravitational lensing by use of the Einstein radius may not be a proper method to investigate the property of dark energy. However, better understanding to the mass profile of clusters in the future or other methods related to arc statistics rather than the distances may be used for constraints on dark energy.

If the Pioneer anomaly has a gravitational origin, it would, according to the equivalence principle, distort the motions of the planets in the Solar System. Since no anomalous motion of the planets has been detected, it is generally believed that the Pioneer anomaly can not originate from a gravitational source in the Solar System. However, this conclusion becomes less obvious when considering models that either imply modifications to gravity over long distances or gravitational sources localized to the outer Solar System, given the uncertainty in the orbital parameters of the outer planets. Following the general assumption that the Pioneer spacecraft move geodesically in a spherically symmetric space-time metric, we derive the metric disturbance that is needed in order to account for the Pioneer anomaly. We then analyze the residual effects on the astronomical observables of the three outer planets that would arise from this metric disturbance, given an arbitrary metric theory of gravity. Providing a method for comparing the computed residuals with actual residuals, our results imply that the presence of a perturbation to the gravitational field necessary to induce the Pioneer anomaly is in conflict with available data for the planets Uranus and Pluto, but not for Neptune. We therefore conclude that the motion of the Pioneer spacecraft must be nongeodesic. Since our results are model-independent within the class of metric theories of gravity, they can be applied to rule out any model of the Pioneer anomaly that implies that the Pioneer spacecraft move geodesically in a perturbed space-time metric, regardless of the origin of this metric disturbance.

The coupling constants $g_L$ and $g_X$ of some versions of the $SU(3{)}_L\otimes U(1{)}_X$ extension of the standard model are related through to relationship $g_X^2/g_L^2={sin}^2{\theta }_W/(1-4{sin}^2{\theta }_W)$. This fact suggest that the $SU(3{)}_L\otimes U(1{)}_X$ gauge symmetry in this class of models can be broken dynamically to the standard model at TeV scale without requiring the introduction of fundamental scalars. This possibility was investigated by Das and Jain who considered the only first version of this class of models. In this brief report we discuss an energy criterion to verify the most probable version of the $SU(3{)}_L\otimes U(1{)}_X$ model that is realized in nature.

We present results for phase structure of lattice QCD with two degenerate flavors ($N_f=2$) of Wilson quarks at finite temperature $T$ and small baryon chemical potential ${\mu }_B$. Using the imaginary chemical potential for which the fermion determinant is positive, we perform simulations at points where the ratios of pseudoscalar meson mass to the vector meson mass $m_{\pi }/m_{\rho }$ are between 0.943(3) and 0.899(4) as well as in the quenched limit. By analytic continuation to real quark chemical potential $\mu$, we obtain the transition temperature as a function of small ${\mu }_B$. We attempt to determine the nature of transition at imaginary chemical potential by histogram, Monte Carlo (MC) history, and finite size scaling. In the infinite heavy quark limit, the transition is of first order. At intermediate values of quark mass $m_q$ corresponding to the ratio of $m_{\pi }/m_{\rho }$ in the range from 0.943(3) to 0.899(4) at $a{\mu }_I=0.24$, the MC simulations show the absence of phase transition.

$B\to \varphi K^{*}$ ($\overline{b}\to \overline{s}$) is three separate decays, one for each polarization of the final-state vector mesons (one longitudinal, two transverse). It is observed that the fraction of transverse decays, $f_T$, and the fraction of longitudinal decays, $f_L$, are roughly equal: $f_T/f_L\simeq 1$, in opposition to the naive expectation that $f_T\ll f_L$. If one requires a single explanation of all polarization puzzles, two possibilities remain within the standard model: penguin annihilation and rescattering. In this paper we examine the predictions of these two explanations for $f_T/f_L$ in $\overline{b}\to \overline{d}$ decays. In $B\to \rho \rho$ decays, only $B_d^0\to {\rho }^0{\rho }^0$ can possibly exhibit a large $f_T/f_L$. In $B$ decays related by U-spin, we find two promising possibilities: (i) $B^{+}\to K^{*0}{\rho }^{+}$ ($\overline{b}\to \overline{s}$) and $B^{+}\to {\overline{K}}^{*0}{K}^{*+}$ ($\overline{b}\to \overline{d}$) and (ii) $B_s\to K^{*0}{\overline{K}}^{*0}$ ($\overline{b}\to \overline{s}$) and $B_d^0\to {\overline{K}}^{*0}{K}^{*0}$ ($\overline{b}\to \overline{d}$). The measurement of $f_T/f_L$ in these pairs of decays will allow us to test penguin annihilation and rescattering. Finally, it is possible to distinguish penguin annihilation from rescattering by performing a time-dependent angular analysis of $B_d^0\to {\overline{K}}^{*0}{K}^{*0}$.

We reexamine the constraints on universal extra dimensional models arising from the inclusive radiative $\overline{B}\to X_s\gamma$ decay. We take into account the leading order contributions due to the exchange of Kaluza-Klein modes as well as the available next-to-next-to-leading order corrections to the $\overline{B}\to X_s\gamma$ branching ratio in the standard model. For the case of one large flat universal extra dimension, we obtain a lower bound on the inverse compactification radius $1/R>600\mathrm{GeV}$ at 95% confidence level that is independent of the Higgs mass.

We develop a model for the weak pion production off the nucleon, which besides the delta pole mechanism [weak excitation of the $\Delta (1232)$ resonance and its subsequent decay into $N\pi$], includes also some background terms required by chiral symmetry. We refit the $C_5^A(q^2)$ form factor to the flux-averaged ${\nu }_{\mu }p\to {\mu }^{-}p{\pi }^{+}$ ANL $q^2$-differential cross section data, finding a substantially smaller contribution of the delta pole mechanism than traditionally assumed in the literature. Within this scheme, we calculate several differential and integrated cross sections, including pion angular distributions, induced by neutrinos and antineutrinos and driven both by charged and neutral currents. In all cases we find that the background terms produce quite significant effects, and that they lead to an overall improved description of the data, as compared to the case where only the delta pole mechanism is considered. We also show that the interference between the delta pole and the background terms produces parity-violating contributions to the pion angular differential cross section, which are intimately linked to $T$-odd correlations in the contraction between the leptonic and hadronic tensors. However, these latter correlations do not imply a genuine violation of time-reversal invariance because of the existence of strong final state interaction effects.

The Hawking effect can be rederived in terms of two-point functions and in such a way that it makes it possible to estimate, within the conventional semiclassical theory, the contribution of ultrashort distances at $I^{+}$ to the Planckian spectrum. The analysis shows that, for Schwarzschild astrophysical black holes, the Hawking radiation (for both bosons and fermions) is very robust up to very high frequencies (typically two orders above Hawking’s temperature). Below this scale, the contribution of ultrashort distances to the spectrum is negligible. We argue, using a simple model with modified two-point functions, that the above result seems to have a general validity and that it is related to the observer independence of the short-distance behavior of the corresponding two-point function. The above suggests that only at high emission frequencies could an underlying quantum theory of gravity potentially predict significant deviations from Hawking’s semiclassical result.

It was argued in literature that traversable wormholes can exist with an arbitrarily small violation of null energy conditions. I show that if the amount of exotic material near the wormhole throat tends to zero, either this leads to a horn instead of a wormhole or the throat approaches the horizon in such a way that infinitely large stresses develop on the throat.

The existence of a population of wandering intermediate mass black holes (IMBHs) is a generic prediction of scenarios that seek to explain the formation of supermassive black holes in terms of growth from massive seeds. The growth of IMBHs may lead to the formation of DM overdensities called “mini-spikes,” recently proposed as ideal targets for indirect DM searches. Current ground-based gamma-ray experiments, however, cannot search for these objects due to their limited field of view, and it might be challenging to discriminate mini-spikes in the Milky Way from the many astrophysical sources that GLAST is expected to observe. We show here that gamma-ray experiments can effectively search for IMBHs in the nearby Andromeda Galaxy (also known as M31), where mini-spikes would appear as a distribution of point-sources, isotropically distributed in a $\approx 3°$ circle around the galactic center. For a neutralinolike DM candidate with a mass $m_{\chi }=150\mathrm{GeV}$, up to 20 sources would be detected with GLAST (at $5\sigma$, in 2 months). With air Cherenkov telescopes such as MAGIC and VERITAS, up to 10 sources might be detected, provided that the mass of neutralino is in the TeV range or above.

We investigate the crossover from Bardeen-Cooper-Schrieffer (BCS) pairing to a Bose-Einstein condensate (BEC) in a relativistic superfluid within a boson-fermion model. The model includes, besides the fermions, separate bosonic degrees of freedom, accounting for the bosonic nature of the Cooper pairs. The crossover is realized by tuning the difference between the boson mass and boson chemical potential as a free parameter. The model yields populations of condensed and uncondensed bosons as well as gapped and ungapped fermions throughout the crossover region for arbitrary temperatures. Moreover, we observe the appearance of antiparticles for sufficiently large values of the crossover parameter. As an application, we study pairing of fermions with imbalanced populations. The model can potentially be applied to color superconductivity in dense quark matter at strong couplings.

Non-Abelian vortices for a supersymmetric $\mathcal{N}=2$ Chern-Simons-Higgs theory are explicitly constructed. We introduce $N$ Higgs fields in the fundamental representation of the $U(N)$ gauge group in order to have a color-flavor $SU(N)$ group remaining unbroken in the asymmetric phase. Bogomol’nyi-like first-order equations are found and rotationally symmetric solutions are proposed. These solutions are shown to be truly non-Abelian by parametrizing them in terms of orientational collective coordinates. The low-energy effective action for the orientational moduli results to be the one-dimensional supersymmetric $\mathcal{N}=2$ ${\mathbf{C}\mathbf{P}}^{N-1}$ model. We analyze the quantum mechanics of this effective theory in the $N=2$ case.

A rather nonstandard quantum representation of the canonical commutation relations of quantum mechanics systems, known as the polymer representation, has gained some attention in recent years, due to its possible relation with Planck scale physics. In particular, this approach has been followed in a symmetric sector of loop quantum gravity known as loop quantum cosmology. Here we explore different aspects of the relation between the ordinary Schrödinger theory and the polymer description. The paper has two parts. In the first one, we derive the polymer quantum mechanics starting from the ordinary Schrödinger theory and show that the polymer description arises as an appropriate limit. In the second part we consider the continuum limit of this theory, namely, the reverse process in which one starts from the discrete theory and tries to recover back the ordinary Schrödinger quantum mechanics. We consider several examples of interest, including the harmonic oscillator, the free particle, and a simple cosmological model.

We study the importance of lattice refinement in achieving a successful inflationary era. We solve, in the continuum limit, the second order difference equation governing the quantum evolution in loop quantum cosmology, assuming both a fixed and a dynamically varying lattice in a suitable refinement model. We thus impose a constraint on the potential of a scalar field, so that the continuum approximation is not broken. Considering that such a scalar field could play the role of the inflaton, we obtain a second constraint on the inflationary potential so that there is consistency with the cosmic microwave background data on large angular scales. For a $m^2{\varphi }^2/2$ inflationary model, we combine the two constraints on the inflaton potential to impose an upper limit on $m$, which is severely fine-tuned in the case of a fixed lattice. We thus conclude that lattice refinement is necessary to achieve a natural inflationary model.