In the framework of Coulomb gauge QCD we explore dynamical breaking of chiral symmetry and screening of the confinement potential at finite density. The screened potential is applied in the study of charmonium dissociation.

Correlators of singlet and octet axial currents, as well as anomaly and pseudoscalar densities have been studied using QCD sum rules. Several of these sum rules are used to determine the couplings $f_{\eta }^8$, $f_{\eta }^0$, $f_{{\eta }^{\prime }}^8$ and $f_{{\eta }^{\prime }}^0$. We find mutually consistent values which are also in agreement with phenomenological values obtained from data on various decay and production rates. While most of the sum rules studied by us are independent of the contributions of direct instantons and screening correction, the singlet-singlet current correlator and the anomaly-anomaly correlator improve by their inclusion.

We present a hybrid RSI/RSII model in which we both solve the hierarchy problem and produce a continuum of Kaluza-Klein graviton modes. In this model, four-dimensional gravity can be reproduced, and the radion mode can be stabilized. We then modify the hybrid gravity model to include $\mathrm{SU}(2{)}_L\times \mathrm{SU}(2{)}_R\times \mathrm{U}(1{)}_{B-L}$ bulk gauge fields. Electroweak symmetry is broken by the choice of appropriate boundary conditions. By adjusting the size of one region of the extra dimension, we show that the $S$ parameter can be decreased while protecting the $\rho$ parameter from corrections. We find that as the $S$ parameter is decreased by $\sim 60\%$, $M_{Z^{\prime }}$ and $M_{W^{\prime }}$ stay below 1800 GeV, protecting unitarity.

We present the results of high-statistics calculations of correlation functions generated with single-baryon interpolating operators on an ensemble of dynamical anisotropic gauge-field configurations generated by the Hadron Spectrum Collaboration using a tadpole-improved clover fermion action and Symanzik-improved gauge action. A total of 292, 500 sets of measurements are made using 1194 gauge configurations of size ${20}^3\times 128$ with an anisotropy parameter $\xi =b_s/b_t=3.5$, a spatial lattice spacing of $b_s=0.1227\pm 0.0008\mathrm{fm}$, and pion mass of $M_{\pi }\sim 390\mathrm{MeV}$. Ground state baryon masses are extracted with fully quantified uncertainties that are at or below the $\sim 0.2\%$-level in lattice units. The lowest-lying negative-parity states are also extracted albeit with a somewhat lower level of precision. In the case of the nucleon, this negative-parity state is above the $N\pi$ threshold and, therefore, the isospin-$\frac{1}{2}$ $\pi N$ $s$-wave scattering phase-shift can be extracted using Lüscher’s method. The disconnected contributions to this process are included indirectly in the gauge-field configurations and do not require additional calculations. The signal-to-noise ratio in the various correlation functions is explored and is found to degrade exponentially faster than naive expectations on many time slices. This is due to backward propagating states arising from the antiperiodic boundary conditions imposed on the quark propagators in the time direction. We explore how best to distribute computational resources between configuration generation and propagator measurements in order to optimize the extraction of single baryon observables.

We construct cosmological spacetimes with null Kasner-like singularities as purely gravitational solutions with no other background fields turned on. These can be recast as anisotropic plane-wave spacetimes by coordinate transformations. We analyze string quantization to find the spectrum of string modes in these backgrounds. The classical string modes can be solved for exactly in these time-dependent backgrounds, which enables a detailed study of the near-singularity string spectrum, (time-dependent) oscillator masses, and wave functions. We find that for low-lying string modes (finite oscillation number), the classical near-singularity string mode functions are nondivergent for various families of singularities. Furthermore, for any infinitesimal regularization of the vicinity of the singularity, we find a tower of string modes of ultrahigh oscillation number which propagate essentially freely in the background. The resulting picture suggests that string interactions are non-negligible near the singularity.

In $\mathcal{N}=2$ supersymmetric QCD with the $\mathrm{U}(N)$ gauge group and $N_f>N$ we study the crossover transition from the weak coupling regime at large $\xi$ to strong coupling at small $\xi$, where $\xi$ is the Fayet-Iliopoulos parameter. We find that at strong coupling a dual non-Abelian weakly coupled $\mathcal{N}=2$ theory exists, which describes low-energy physics at small $\xi$. The dual gauge group is $\mathrm{U}(N_f-N)$, and the dual theory has $N_f$ flavors of light dyons, to be compared with $N_f$ quarks in the original$\mathrm{U}(N)$ theory. Both, the original and dual theories are Higgsed and share the same global symmetry $\mathrm{SU}(N)\times \mathrm{SU}(N_f-N)\times \mathrm{U}(1)$, albeit the physical meaning of the $\mathrm{SU}(N)$ and $\mathrm{SU}(N_f-N)$ factors is different in the large- and small-$\xi$ regimes. Both regimes support non-Abelian semilocal strings. In each of these two regimes particles that are in the adjoint representations with respect to one of the factor groups exist in two varieties: elementary fields and composite states bound by strings. These varieties interchange upon transition from one regime to the other. We conjecture that the composite stringy states can be related to Seiberg’s $M$ fields. The bulk duality that we observed translates into a two-dimensional duality on the world sheet of the non-Abelian strings. At large $\xi$ the internal dynamics of the semilocal non-Abelian strings is described by the sigma model of $N$ orientational and ($N_f-N$) size moduli, while at small $\xi$ the roles of orientational and size moduli interchange. The Bogomol’nyi-Prasad-Sommerfield spectra of two dual sigma models (describing confined monopoles/dyons of the bulk theory) coincide. It would be interesting to trace parallels between the non-Abelian duality we found and string theory constructions.

We show a uniqueness theorem for charged rotating black holes in the bosonic sector of five-dimensional minimal supergravity. More precisely, under the assumptions of the existence of two commuting axial isometries and spherical topology of horizon cross sections, we prove that an asymptotically flat, stationary charged rotating black hole with finite temperature in the five-dimensional Einstein-Maxwell-Chern-Simons theory is uniquely characterized by the mass, charge, and two independent angular momenta and therefore is described by the Chong-Cvetič-Lü-Pope solution. We also discuss a generalization of our uniqueness theorem for spherical black holes to the case of black rings.

The Hilbert-Huang transform is a novel, adaptive approach to time series analysis that does not make assumptions about the data form. Its adaptive, local character allows the decomposition of nonstationary signals with high time-frequency resolution but also renders it susceptible to degradation from noise. We show that complementing the Hilbert-Huang transform with techniques such as zero-phase filtering, kernel density estimation and Fourier analysis allows it to be used effectively to detect and characterize signals with low signal-to-noise ratios.

We apply the proximity force approximation, which is widely used for the calculation of the Casimir force between bodies with nonplanar boundary surfaces, to gravitational and Yukawa-type interactions. It is shown that for the gravitational force in a sphere-plate configuration the general formulation of the proximity force approximation is well applicable. For a Yukawa-type interaction we demonstrate the validity of both the general formulation of the proximity force approximation and a simple mapping between the sphere-plate and plate-plate configurations. The claims to the contrary in some recent literature are thus incorrect. Our results justify the constraints on the parameters of non-Newtonian gravity previously obtained from the indirect dynamic measurements of the Casimir pressure.

It is shown that the addition of a topological invariant (Gauss-Bonnet term) to the anti–de Sitter gravity action in four dimensions recovers the standard regularization given by the holographic renormalization procedure. This crucial step makes possible the inclusion of an odd parity invariant (Pontryagin term) whose coupling is fixed by demanding an asymptotic (anti) self-dual condition on the Weyl tensor. This argument allows one to find the dual point of the theory where the holographic stress tensor is related to the boundary Cotton tensor as $T_j^i=\pm ({\ell }^2/8\pi G)C_j^i$, which has been observed in recent literature in solitonic solutions and hydrodynamic models. A general procedure to generate the counterterm series for anti–de Sitter gravity in any even dimension from the corresponding Euler term is also briefly discussed.

It is shown that the recently detected acceleration of the Uuniverse can be understood by considering a modification of the teleparallel equivalent of general relativity, with no need of dark energy. The solution also exhibits phases dominated by matter and radiation as expected in the standard cosmological evolution. We perform a joint analysis with measurements of the most recent type Ia supernovae, baryon acoustic oscillation peak, and estimates of the cosmic microwave background shift parameter data to constrain the only new parameter this theory has.

We propose a field theory model for dark energy and dark matter in interaction. Comparing the classical solutions of the field equations with the observations of the CMB shift parameter, baryonic acoustic oscillations, lookback time, and the Gold supernovae sample, we observe a possible interaction between dark sectors with energy decay from dark energy into dark matter. The observed interaction provides an alleviation to the coincidence problem.

Based upon the rate equations for the photon distribution function obtained in the previous paper, we study the formal solutions in three different representation forms for the Sunyaev-Zeldovich effect. By expanding the formal solution in the operator representation in powers of both the derivative operator and electron velocity, we derive a formal solution that is equivalent to the Fokker-Planck expansion approximation. We extend the present formalism to the kinematical Sunyaev-Zeldovich effect. The properties of the frequency redistribution functions are studied. We find that the kinematical Sunyaev-Zeldovich effect is described by the redistribution function related to the electron pressure. We also solve the rate equations numerically. We obtain the exact numerical solutions, which include the full-order terms in powers of the optical depth.

We consider the impact of imposing generalized $CP$ symmetries on the Higgs sector of the two-Higgs-doublet model, and identify three classes of symmetries. Two of these classes constrain the scalar potential parameters to an exceptional region of parameter space, which respects either a $Z_2$ discrete flavor symmetry or a $U(1)$ symmetry. We exhibit a basis-invariant quantity that distinguishes between these two possible symmetries. We also show that the consequences of imposing these two classes of $CP$ symmetry can be achieved by combining Higgs family symmetries, and that this is not possible for the usual $CP$ symmetry. We comment on the vacuum structure and on renormalization in the presence of these symmetries. Finally, we demonstrate that the standard $CP$ symmetry can be used to build all the models we identify, including those based on Higgs family symmetries.

A weakly interacting massive particle (WIMP) weighing only a few GeV has been invoked as an explanation for the signal from the DAMA/LIBRA experiment. We show that the data from DAMA/LIBRA are now powerful enough to strongly constrain the properties of any putative WIMP. Accounting for the detailed recoil spectrum, a light WIMP with a Maxwellian velocity distribution and a spin-independent interaction cannot account for the data. Even neglecting the spectrum, significant parameter space is excluded by a limit that can be derived from the DAMA unmodulated signal at low energies. Appreciable modification to the astrophysics or particle physics can open light mass windows.

We introduce and implement a new, extended approach to placing bounds on trilinear $R$-parity violating ($\mathrm{R̸}$) couplings. We focus on a limited set of leptonic and semileptonic processes involving neutrinos, combining multidimensional plotting, and cross-checking constraints from different experiments. This allows us to explore new regions of parameter space and to relax a number of bounds given in the literature. We look for qualitatively different results compared to those obtained previously using the assumption that a single coupling dominates the $R$-parity violating contributions to a process (SCD). By combining results from several experiments, we identify regions in parameter space where two or more parameters approach their maximally allowed values. In the same vein, we show a circumstance where consistency between independent bounds on the same combinations of trilinear coupling parameters implies mass constraints among slepton or squark masses. Though our new bounds are in most cases weaker than the SCD bounds, the largest deviations we find on individual parameters are factors of two, thus indicating that a conservative, order of magnitude bound on an individual coupling is reliably estimated by making the SCD assumption.

We consider a supergravity scenario, with universal scalar and gaugino masses at high scale, with a right-chiral neutrino superfield included in the spectrum. Such a scenario can have the lightest supersymmetric particle (LSP) dominated by the right sneutrino and a stau as the next-to lightest supersymmetric particle (NLSP). Since decays of all particles into the LSP are suppressed by the neutrino Yukawa coupling, the signal of supersymmetry consists of charged tracks of stable particles in the muon chamber. We demonstrate how a neutralino decaying into a tau and the stau NLSP can be fully reconstructed over substantial areas in the supergravity parameter space. We also suggest event selection criteria for eliminating backgrounds, including combinatorial ones, and use a new method for the extraction of the mass of the stau NLSP, using its three-momentum as obtained from the curvature of the charged track.

A secluded $\mathrm{U}(1{)}_S$ gauge field, kinetically mixed with standard model hypercharge, provides a “portal” mediating interactions with a hidden sector at the renormalizable level, as recently exploited in the context of weakly interacting massive particle dark matter. The $\mathrm{U}(1{)}_S$ symmetry-breaking scale may naturally be suppressed relative to the weak scale, and so this sector is efficiently probed by medium-energy $e^{+}{e}^{-}$ colliders. We study the collider signatures of the minimal $\mathrm{U}(1{)}_S$ model, focusing on the reach of $B$-factory experiments such as BABAR and BELLE. In particular, we show that Higgs strahlung in the secluded sector can lead to multilepton signatures, which probe the natural range for the kinetic mixing angle $\kappa \sim {10}^{-2}–{10}^{-3}$ over a large portion of the kinematically accessible parameter space.