We analyze the dependence of the QCD transition temperature on the quark (or pion) mass. We find that a linear sigma model, which links the transition to chiral symmetry restoration, predicts a much stronger dependence of $T_c$ on $m_{\pi }$ than seen in present lattice data for $m_{\pi }\gtrsim 0.4\mathrm{G}\mathrm{e}\mathrm{V}$. On the other hand, working down from $m_{\pi }=\infty$, an effective Lagrangian for the Polyakov loop requires only small explicit symmetry breaking, $b_1\sim \exp (-m_{\pi })$, to describe $T_c(m_{\pi })$ in the above mass range. Physically, this is a consequence of the flat potential (large correlation length) for the Polyakov loop in the three-color pure gauge theory at $T_c$. We quantitatively estimate the end point of the line of first-order deconfining phase transitions: $m_{\pi }\simeq 4.2\sqrt{\sigma }\simeq 1.8\mathrm{G}\mathrm{e}\mathrm{V}$ and $T_c\simeq 240\mathrm{M}\mathrm{e}\mathrm{V}$ for three flavors and three colors.

We study the nucleon contribution to the electromagnetic vertex function of neutrinos that propagate in a matter background in the presence of a magnetic field. Starting from the one-loop expression for the corresponding terms of the vertex function, and taking into account the anomalous magnetic coupling of the nucleons, we calculate the $B$-dependent part of the form factors that determine the induced charge of the neutrino. A formula for the neutrino induced charge is obtained, and it is evaluated for various illustrative situations. The terms due to the nucleons can be important in some cases, depending on the physical conditions of the environment.

We consider the production of neutralino, chargino, and charged Higgs boson pairs in the Minimal Supersymmetric Standard Model (MSSM) framework at future $e^{+}{e}^{-}$ colliders. We show that, for c.m. energies in the 1 TeV range and in a moderately light supersymmetry (SUSY) scenario, a combined analysis of the slopes of these production cross sections could lead to a strong consistency test involving the soft supersymmetric breaking parameters $M_1$, $M_2$, the Higgsino parameter $\mu$, and $\tan \beta$.

We have developed a formalism to study nonadiabatic, nonradial oscillations of nonrotating compact stars in the frequency domain, including the effects of thermal diffusion in the framework of general relativistic perturbation theory. When a general equation of state depending on temperature is used, the perturbations of the fluid result in heat flux which is coupled with the space-time geometry through the Einstein field equations. Our results show that the frequency of the first pressure (p) and gravity (g) oscillation modes is significantly affected by thermal diffusion, while that of the fundamental (f) mode is basically unaltered due to the global nature of that oscillation. The damping time of the oscillations is generally much smaller than in the adiabatic case (more than 2 orders of magnitude for the p- and g-modes) reflecting the effect of thermal dissipation. Both the isothermal and adiabatic limits are recovered in our treatment and we study in more detail the intermediate regime. Our formalism finds its natural astrophysical application in the study of the oscillation properties of newly born neutron stars, neutron stars with a deconfined quark core phase, or strange stars which are all promising sources of gravitational waves with frequencies in the band of the first generation and advanced ground-based interferometric detectors.

We explicate the origin of the temperature quadrupole in the adiabatic dark energy model and explore the mechanism by which scale invariant isocurvature dark energy perturbations can lead to its sharp suppression. The model requires anticorrelated curvature and isocurvature fluctuations and is favored by the Wilkinson Microwave Anisotropy Probe data at about the 95% confidence level in a flat scale invariant model. In an inflationary context, the anticorrelation may be established if the curvature fluctuations originate from a variable decay rate of the inflaton; such models however tend to overpredict gravitational waves. This isocurvature model can in the future be distinguished from alternatives involving a reduction in large scale power or modifications to the sound speed of the dark energy through the polarization and its cross correlation with the temperature. The isocurvature model retains the same polarization fluctuations as its adiabatic counterpart but reduces the correlated temperature fluctuations. We present a pedagogical discussion of dark energy fluctuations in a quintessence and k-essence context in the Appendix.

Predictions for $e^{+}{e}^{-}\to J/\psi {\eta }_c$ from previous studies are made by taking charmonia as a nonrelativistic bound state and by using nonrelativistic QCD (NRQCD) approach. The predicted cross section is smaller by an order of magnitude than the experimentally observed cross section. We study the process by taking charm quark as a light quark and use light-cone wave functions to parameterize nonperturbative effects related to charmonia. The total cross section of $e^{+}{e}^{-}\to J/\psi {\eta }_c$ can be predicted, if these wave functions are known. Motivated by studies of light-cone wave functions of light hadrons, we make a reasonable assumption of the forms of light-cone wave functions. With these light-cone wave functions we can obtain the cross section which is closer to the experimentally observed than that from the NRQCD approach. We also discuss in detail the difference between two approaches.

We investigate dynamical chiral symmetry breaking in unquenched ${\mathrm{Q}\mathrm{E}\mathrm{D}}_3$ using the coupled set of Dyson-Schwinger equations for the fermion and photon propagators. For the fermion-photon interaction we employ an ansatz which satisfies its Ward-Green-Takahashi identity. We present self-consistent analytical solutions in the infrared as well as numerical results for all momenta. In Landau gauge, we find a phase transition at a critical number of flavors of $N_f^{\mathrm{c}\mathrm{r}\mathrm{i}\mathrm{t}}\approx 4$. In the chirally symmetric phase the infrared behavior of the propagators is described by power laws with interrelated exponents. For $N_f=1$ and $N_f=2$ we find small values for the chiral condensate in accordance with bounds from recent lattice calculations. We investigate the Dyson-Schwinger equations in other linear covariant gauges as well. A comparison of their solutions to the accordingly transformed Landau gauge solutions shows that the quenched solutions are approximately gauge covariant, but reveals a significant amount of violation of gauge covariance for the unquenched solutions.

We calculate the two-loop diagrams that give a nonzero contribution to the electric dipole moment $d_l$ of a charged lepton $l$ due to possible Majorana masses of neutrinos. Using the example with one generation of the standard model leptons and two heavy right-handed neutrinos, we demonstrate that the nonvanishing result for $d_l$ first appears in order $O(m_l{m}_{\nu }^2{G}_F^2)$, where $m_{\nu }$ is the mass of the light neutrino and the see-saw type relation is imposed. This effect is beyond the reach of presently planned experiments.

Species doubling is a problem that infects most numerical methods that use a spatial lattice. An understanding of species doubling can be found in the Nielsen-Ninomiya theorem which gives a set of conditions that require species doubling. The transverse lattice approach to solving field theories, which has at least one spatial lattice, fails one of the conditions of the Nielsen-Ninomiya theorem nevertheless one still finds species doubling for the standard Lagrangian formulation of the transverse lattice. We will show that the Supersymmetric Discrete Light Cone Quantization (SDLCQ) formulation of the transverse lattice does not have species doubling.

We construct several classes of exact supersymmetric supergravity solutions describing D4 branes polarized into NS5 branes and F-strings polarized into D2 branes. These setups belong to the same universality class as the perturbative solutions used by Polchinski and Strassler to describe the string dual of $\mathcal{N}=1^{*}$ theories. The D4-NS5 setup can be interpreted as a string dual to a confining $4+1$ dimensional theory with 8 supercharges, whose properties we discuss. By T-duality, our solutions give Type IIB supersymmetric backgrounds with polarized branes.

The path integral for space-time noncommutative theory is formulated by means of Schwinger’s action principle, which is based on the equations of motion and a suitable ansatz of asymptotic conditions. The resulting path integral has essentially the same physical basis as the Yang-Feldman formulation. It is first shown that higher derivative theories are neatly dealt with by the path integral formulation, and the underlying canonical structure is recovered by the Bjorken-Johnson-Low (BJL) prescription from correlation functions defined by the path integral. A simple theory which is nonlocal in time is then analyzed for an illustration of the complications related to quantization, unitarity, and positive energy conditions. From the viewpoint of the BJL prescription, the naive quantization in the interaction picture is justified for space-time noncommutative theory but not for the simple theory nonlocal in time. We finally show that the perturbative unitarity and the positive energy condition, in the sense that only the positive energy flows in the positive time direction for any fixed time slice in space-time, are not simultaneously satisfied for space-time noncommutative theory by the known methods of quantization.

We consider Double Quintessence models for which the Dark Energy sector consists of two coupled scalar fields. We study, in particular, the possibility to have a transient acceleration in these models. In both Double Quintessence models studied here, it is shown that, if acceleration occurs, it is necessarily transient. We consider also the possibility to have transient acceleration in two one-field models, the Albrecht-Skordis model and the pure exponential. Using separate conservative constraints (marginalizing over the other parameters) on the effective equation of state $w_{\mathrm{e}\mathrm{f}\mathrm{f}}$, the relative density of the Dark Energy ${\Omega }_{Q,0}$ and the present age of the Universe, we construct scenarios with a transient acceleration that has already ended at the present time, and even with no acceleration at all, but a less conservative analysis using the cosmic microwave background data rules out the last possibility. The scenario with a transient acceleration ended by today can be implemented for the range of cosmological parameters ${\Omega }_{m,0}\gtrsim 0.35$ and $h\lesssim 0.68$.

The generation of large-scale magnetic fields is studied in dilaton electromagnetism in noncommutative inflationary cosmology, taking into account the effects of the spacetime uncertainty principle motivated by string theory. We show that it is possible to generate large-scale magnetic fields with sufficient strength to account for the observed fields in galaxies and clusters of galaxies through only adiabatic compression without dynamo amplification mechanism in models of power-law inflation based on spacetime noncommutativity without introducing a huge hierarchy between the dilaton’s potential and its coupling to the electromagnetic fields.

We consider the consequences of a neutral dark-matter particle with a nonzero electric and/or magnetic dipole moment. Theoretical constraints, as well as constraints from direct searches, precision tests of the standard-model, the cosmic microwave background and matter power spectra, and cosmic gamma rays, are included. We find that a relatively light particle with mass between an MeV and a few GeV and an electric or magnetic dipole as large as $\sim 3\times {10}^{-16}e\mathrm{c}\mathrm{m}$ (roughly $1.6\times {10}^{-5}{\mu }_B$) satisfies all experimental and observational bounds. Some of the remaining parameter space may be probed with forthcoming more sensitive direct searches and with the Gamma-Ray Large Area Space Telescope.

This paper describes an incoherent method to search for continuous gravitational waves based on the Hough transform, a well-known technique used for detecting patterns in digital images. We apply the Hough transform to detect patterns in the time-frequency plane of the data produced by an earth-based gravitational wave detector. Two different flavors of searches will be considered, depending on the type of input to the Hough transform: either Fourier transforms of the detector data or the output of a coherent matched-filtering type search. We present the technical details for implementing the Hough transform algorithm for both kinds of searches, their statistical properties, and their sensitivities.

Using nontrivial mathematical properties of a class of nonlinear evolution equations, we obtain the universal terms in the asymptotic expansion in rapidity of the saturation scale and of the unintegrated gluon density from the Balitskiĭ-Kovchegov equation. These terms are independent of the initial conditions and of the details of the equation. The last subasymptotic terms are new results and complete the list of all possible universal contributions. Universality is interpreted in a general qualitative picture of high-energy scattering, in which a scattering process corresponds to a tree structure probed by a given source.

We explore dark matter in the finely-tuned minimal supersymmetric standard model (MSSM) recently proposed by Arkani-Hamed and Dimopoulos. Relative to the MSSM, there are fewer particles at freeze-out, so the calculation of the relic abundance simplifies. Similarly, the predictions for direct detection of the dark matter sharpen. There is a large region of mixed bino—higgsino dark matter where the lightest supersymmetric particle will be accessible at both the LHC and future direct detection experiments, allowing for a conclusive identification of the dark matter particle. Typical dark matter-nucleon cross sections are ${10}^{-45}-{10}^{-44}{\mathrm{c}\mathrm{m}}^2$. This model also possesses a novel region where the dark matter annihilates via an $s$-channel Higgs boson resonance.

In realistic grand unified models there are typically extra vectorlike matter multiplets at the GUT-scale that are needed to explain the family hierarchy. These contain neutrinos that, when integrated out, can modify the usual neutrino seesaw formula. A general analysis is given. It is noted that such modifications can explain why the neutrinos do not exhibit a strong family hierarchy like the other types of fermions.

It appears well accepted in the literature that the correlator of Polyakov loops in a finite temperature system decays with the average free energy of the static quark-antiquark system and can be decomposed into singlet and adjoint (or octet for QCD) contributions. By fixing a gauge respecting the transfer matrix, attempts have been made to extract those contributions separately. In this paper we point out that the average and adjoint channels of Polyakov loop correlators are misconceptions. We show analytically that all channels receive contributions from singlet states only, and give a corrected definition of the singlet free energy. We verify this finding by simulations of the 3D SU(2) pure gauge theory in the zero-temperature limit, which allows one to cleanly extract the ground state exponents and the nontrivial matrix elements. The latter account for the difference between the channels observed in previous simulations.

In this article, we calculate the nonfactorizable soft contributions in the $B\to {\eta }_{c}K,{\chi }_{c0}K$ decays with the light-cone QCD sum rules approach. Our results show that the nonfactorizable corrections from the soft-gluon exchanges in the decay $B\to {\eta }_{c}K$ are of $(15-30)\%$ and should be taken into account. As for the decay $B\to {\chi }_{c0}K$, the factorizable contributions are zero and the nonfactorizable contributions from the soft hadronic matrix elements are too small to accommodate the experimental data.