We discuss observational constraints coming from CMB and type Ia supernovae for the model of an accelerated universe produced by gravitational leakage into extra dimensions. Our fits indicate that the model is currently in agreement with the data. We also give the equations governing the evolution of cosmological perturbations. Future observations will be able to severely constrain the model.

In this paper we study the regular self-gravitating ’t Hooft–Polyakov magnetic monopole in a global monopole spacetime. We show that, for the large distance, the structure of the manifold corresponds to the Reissner-Nordström spacetime with a solid angle deficit factor. Although we analyze static and spherically symmetric solutions, it is not possible to solve analytically the system of coupled differential equations and only numerical evaluations can provide detailed information about the behavior of this system at the neighborhood of the defect’s core. So, for this reason we solve numerically the set of differential equations for the metric tensor and for the matter fields for different values of the Higgs field vacuum expectation value η and the self-coupling constant λ.

Theories with large extra dimensions provide the possibility that a flavor neutrino, localized in a $3+1$ brane, can mix with a singlet neutrino living in the bulk. This mixing leads to unconventional patterns of neutrino matter oscillations and we examine in detail how these oscillations depend upon two parameters: the brane-bulk coupling ξ and the effective mass μ of the flavor neutrino inside matter. We find that high energy $(E>~50\hspace{0.5em}\mathrm{GeV})$ ${\nu }_{\mu }$ neutrinos, to be detected by neutrino telescopes, can give signals of extra dimensions. With a $1\hspace{0.5em}{\mathrm{km}}^3$ neutrino telescope extra dimensions with a radius down to $1\hspace{0.5em}\mu \mathrm{m}$ can be tested directly, while for a smaller radius indirect evidence can be established.

We develop both the gravity and field theory sides of the Karch-Randall conjecture that the near-horizon description of a certain D5-D3 brane configuration in string theory, realized as ${\mathrm{AdS}}_5\times {\mathrm{S}}^5$ bisected by an ${\mathrm{AdS}}_4\times {\mathrm{S}}^2$ “brane,” is dual to $\mathcal{N}=4\mathrm{}$ super Yang-Mills theory in ${\mathbf{R}}^4$ coupled to an ${\mathbf{R}}^3$ defect. We propose a complete Lagrangian for the field theory dual, a novel “defect superconformal field theory” wherein a subset of the fields of $\mathcal{N}=4\mathrm{}$ SYM theory interacts with a $d=3\mathrm{}\hspace{0.5em}\mathrm{SU}\left(N\right)\mathrm{}$ fundamental hypermultiplet on the defect preserving conformal invariance and 8 supercharges. The Kaluza-Klein reduction of wrapped D5 modes on ${\mathrm{AdS}}_4\times {\mathrm{S}}^2$ leads to towers of short representations of $OSp\left(4\mathrm{}|4\right),$ and we construct the map to a set of dual gauge-invariant defect operators ${\mathcal{O}}_3$ possessing integer conformal dimensions. Gravity calculations of $〈{\mathcal{O}}_4〉$ and $〈{\mathcal{O}}_4{\mathcal{O}}_3〉$ are given. Spacetime and N dependence matches expectations from DCFT, while the behavior as functions of $\lambda {=g}^{2}N$ at strong and weak coupling is generically different. We comment on a class of correlators for which a nonrenormalization theorem may still exist. Partial evidence for the conformality of the quantum theory is given, including a complete argument for the special case of a $U\left(1\right)\mathrm{}$ gauge group. Some weak coupling arguments which illuminate the duality are presented.

We apply the Gyulassy-Levai-Vitev reaction operator formalism to compute the effects of multiple elastic scatterings of on-shell partons propagating through dense matter. We derive the elastic reaction operator and demonstrate that the recursion relations have a closed form solution that reduces to the familiar Glauber form. We also investigate the accuracy of the Gaussian dipole approximation for the parton transverse momentum broadening.

Loop quantum gravity is based on a classical formulation of $3+1$ gravity in terms of a real $\mathrm{SU}\left(2\right)\mathrm{}$ connection. Linearization of this classical formulation about a flat background yields a description of linearized gravity in terms of a real $U\left(1\right)\mathrm{}\times U\left(1\right)\mathrm{}\times U\left(1\right)\mathrm{}$ connection. A “loop” representation, in which holonomies of this connection are unitary operators, can be constructed. These holonomies are not well defined operators in the standard graviton Fock representation. We generalize our recent work on photons and $U\left(1\right)\mathrm{}$ holonomies to show that Fock space gravitons are associated with distributional states in the $U\left(1\right)\mathrm{}\times U\left(1\right)\mathrm{}\times U\left(1\right)\mathrm{}$ loop representation. Our results may illuminate certain aspects of the much deeper (and as yet unkown) relation between gravitons and states in nonperturbative loop quantum gravity. This work leans heavily on earlier seminal work by Ashtekar, Rovelli and Smolin (ARS) on the loop representation of linearized gravity using complex connections. In the last part of this work we show that the loop representation based on the real $U\left(1\right)\mathrm{}\times U\left(1\right)\mathrm{}\times U\left(1\right)\mathrm{}$ connection also provides a useful kinematic arena in which it is possible to express the ARS complex connection-based results in the mathematically precise language currently used in the field.

The (zeroth-order) energy of a particle in the background of a black hole is given by Carter’s integrals. However, exact calculations of a particle’s self-energy (first-order corrections) are still beyond our present reach in many situations. In this paper we use Hawking’s area theorem in order to derive bounds on the self-energy of a particle in the vicinity of a black hole. Furthermore, we show that self-energy corrections must be taken into account in order to guarantee the validity of Penrose’s cosmic censorship conjecture.

Earth absorbs ${\nu }_e$ and ${\nu }_{\mu }$ of energies above about 100 TeV. As is well known, although ${\nu }_{\tau }$ will also disappear through charged-current interactions, the ${\nu }_{\tau }$ flux will be regenerated by prompt tau decays. We show that this process also produces relatively large fluxes of secondary ${\overline{\nu }}_e$ and ${\overline{\nu }}_{\mu },$ greatly enhancing the detectability of the initial ${\nu }_{\tau }.$ This is particularly important because at these energies ${\nu }_{\tau }$ is a significant fraction of the expected astrophysical neutrino flux, and only a tiny portion of the atmospheric neutrino flux.

We consider the $Z^{\prime }/Z$ mass hierarchy in a supersymmetric model in which the ${U\left(1\right)\mathrm{}}^{\prime }$ is broken in a secluded sector coupled to the ordinary sector only by gauge and possibly soft terms. A large mass hierarchy can be achieved while maintaining the normal sparticle spectra if there is a direction in which the tree level potential becomes flat when a particular Yukawa coupling vanishes. We describe the conditions needed for the desired breaking pattern, to avoid unwanted global symmetries, and for an acceptable effective μ parameter. The electroweak breaking is dominated by A terms rather than scalar masses, leading to $\tan \beta \simeq 1.$ The spectrum of the symmetry breaking sector is displayed. There is significant mixing between the MSSM particles and new standard model singlets, for both the Higgs scalars and the neutralinos. A larger Yukawa coupling for the effective μ parameter is allowed than in the NMSSM because of the ${U\left(1\right)\mathrm{}}^{\prime }$ contribution to the running from a high scale. The upper bound on the tree-level mass of the lightest $\mathrm{CP}$ even Higgs doublet mass is about $c\times 174\hspace{0.5em}\mathrm{GeV},$ where c is of order unity, but the actual mass eigenvalues are generally smaller because of singlet mixing.

Lepton collider experiments can search for light technipions in final states made striking by the presence of an energetic photon: $e^{+}{e}^{-}\to \gamma {\Pi }_{\mathrm{T}}.$ To date, searches have focused on either production through anomalous coupling of the technipions to electroweak gauge bosons or on production through a technivector meson $({\rho }_{\mathrm{T}},{\omega }_{\mathrm{T}})$ resonance. This paper creates a combined framework in which both contributions are included. This will allow stronger and more accurate limits on technipion production to be set using existing data from CERN LEP or future data from a higher-energy linear collider. We provide explicit formulas and sample calculations (analytic and PYTHIA) in the framework of the technicolor straw man model, a model that includes light technihadrons.

Numerical evaluation of the overlap Dirac operator is difficult since it contains the sign function $\epsilon {(H}_{\mathrm{w}})$ of the Hermitian Wilson-Dirac operator $H_{\mathrm{w}}$ with a negative mass term. The problems are due to $H_{\mathrm{w}}$ having very small eigenvalues on the equilibrium background configurations generated in current day Monte Carlo simulations. Since these are a consequence of the lattice discretization and do not occur in the continuum version of the operator, we investigate in this paper to what extent the numerical evaluation of the overlap can be accelerated by making the Wilson-Dirac operator more continuum-like. Specifically, we study the effect of including the clover term in the Wilson-Dirac operator and smearing the link variables in the irrelevant terms. In doing so, we have obtained a factor of 2 speedup by moving from the Wilson action to a fat link irrelevant clover action as the overlap kernel.

It has been pointed out recently by Chanowitz that the $\overrightarrow{Z}b\overline{b}$ decay asymmetry poses a problem for the standard model whether or not it is genuine. If this conflict is interpreted as new physics in the b-quark couplings, it suggests a rather large right handed coupling of the b-quark to the Z boson. We show that it is possible to accommodate this result in left-right models that single out the third generation.

We have carried out the largest search for stable particles with fractional electric charge, based on an oil drop method that incorporates a horizontal electric field and upward air flow. No evidence for such particles was found, giving a 95% confidence level upper limit of $1.17\times {10}^{-22}$ particles per nucleon on the abundance of fractional charge particles in silicone oil for $0.18e<~|Q_{\mathrm{residual}}|<~0.82e.$ Since this is the first use of this new method we describe the advantages and limitations of the method.

We study the response of the QCD vacuum to strong magnetic fields, using a potential model for the quark-antiquark interaction. We find that production of spin-polarized $uū$ pairs is energetically favorable for fields $B>\mathrm{}{B}_{\mathrm{crit}}\sim 10\hspace{0.5em}{\mathrm{GeV}}^2.$ We contrast the resulting $uū$ condensate with the quark condensate which is present at zero magnetic field, and we estimate the corresponding magnetization as a function of B.

We show that all correct results obtained by applying quantum field theory to neutrino oscillations can be understood in terms of a single oscillation formula. In particular, the model proposed by Grimus and Stockinger is shown to be a subcase of the model proposed by Giunti, Kim and Lee, while the new oscillation formulas proposed by Ioannisian and Pilaftsis and by Shtanov are disproved. We derive an oscillation formula without making any relativistic assumption and taking into account the dispersion, so that the result is valid for both neutrinos and mesons. This unification gives a stronger phenomenological basis to the neutrino oscillation formula. We also prove that the coherence length can be increased without bound by more accurate energy measurements. Finally, we insist on the wave packet interpretation of the quantum field treatment of oscillations.

In this paper, $B=3\mathrm{}$ soliton solutions with tetrahedral symmetry are obtained numerically in the chiral quark soliton model using the rational map ansatz. The solution exhibits a triply degenerate bound spectrum of the quark orbits in the background of tetrahedrally symmetric pion field configuration. The corresponding baryon density is tetrahedral in shape. Our numerical technique is independent of the baryon number and its application to $B>~4$ is straightforward.

It was shown by Ford and Roman in 1996 that quantum field theory severely constrains wormhole geometries on a macroscopic scale. The first part of this paper discusses a wide class of wormhole solutions that meet these constraints. The type of shape function used is essentially generic. The constraints are then discussed in conjunction with various redshift functions. Violations of the weak energy condition and traversability criteria are also considered. The second part of the paper analyzes analogous time-dependent (dynamic) wormholes with the aid of differential forms. It is shown that a violation of the weak energy condition is not likely to be avoidable even temporarily.

We obtain an analytic approximation for the effective action of a quantum scalar field in a general static two-dimensional spacetime. We apply this to the dilaton gravity model resulting from the spherical reduction of a massive, non-minimally coupled scalar field in the four-dimensional Schwarzschild geometry. Careful analysis near the event horizon shows the resulting two-dimensional system to be regular in the Hartle-Hawking state for general values of the field mass, coupling, and angular momentum, while at spatial infinity it reduces to a thermal gas at the black-hole temperature.

It is widely thought that neutralinos, the lightest supersymmetric particles, could comprise most of the dark matter. If so, then dark halos will emit radio and gamma ray signals initiated by neutralino annihilation. A particularly promising place to look for these indicators is at the center of the local group dwarf spheroidal galaxy Draco, and recent measurements of the motion of its stars have revealed it to be an even better target for dark matter detection than previously thought. We compute limits on WIMP properties for various models of Draco’s dark matter halo. We find that if the halo is nearly isothermal, as the new measurements indicate, then current gamma ray flux limits prohibit much of the neutralino parameter space. If Draco has a moderate magnetic field, then current radio limits can rule out more of it. These results are appreciably stronger than other current constraints, and so acquiring more detailed data on Draco’s density profile may become one of the most promising avenues for identifying dark matter.