In this Letter, we compute the corrections to the Cardy-Verlinde formula of the $d$-dimensional Schwarzschild black hole. These corrections stem from the generalized uncertainty principle. Then we show one can take into account the generalized uncertainty principle corrections of the Cardy-Verlinde entropy formula by just redefining the Virasoro operator $L_0$ and the central charge $c$.

We perform the matching required to compute the leading effective boundary contribution to the QED Lagrangian in the presence of a conducting surface, once the electron is integrated out. Our result resolves a confusion in the literature concerning the interpretation of the leading such correction to the Casimir energy. It also provides a useful theoretical laboratory for brane-world calculations in which kinetic terms are generated on the brane, since a lot is known about QED near boundaries.

We study the $O(N)$ linear sigma model in $1+1$ dimensions by using the two-particle irreducible formalism of Cornwall, Jackiw and Tomboulis in order to evaluate the effective potential at finite temperature. At next-to-leading order in a $1/N$ expansion, one has to include the sums over necklace and generalized “sunset” diagrams. We find that—in contrast to the Hartree approximation—there is no spontaneous symmetry breaking in this approximation, as to be expected for the exact theory. The effective potential becomes convex throughout for all parameter sets which include $N=4,10,100$, couplings $\lambda =0.1,0.5$ and temperatures between $0.3$ and $1$ (in arbitrary units). The Green's functions obtained by solving the Schwinger-Dyson equations are enhanced in the infrared region. We also compare the effective potential as a function of the external field $\varphi$ with those obtained in the one-particle irreducible and two-particle point-irreducible expansions.

We study gravitational collapse of rapidly rotating relativistic polytropes of adiabatic indices $\Gamma =1.5$ and 2. The nondimensional spin parameter of the system $q\equiv J/M^2$ where $J$ and $M$ are the total angular momentum and the gravitational mass is set to be larger than unity. First, analyzing initial distributions of mass and spin parameters inside the stars, we predict the final outcome after the collapse proposing a new criterion for direct black hole formation as $q_c<1$ where $q_c$ denotes an effective spin parameter of the stellar central region. To confirm our predictions, we then perform fully general relativistic simulations assuming axial and equatorial symmetries. It is found that in contrast with previous conclusions for the criterion of no black hole formation, a black hole is formed even from a star with $q>1$ if the condition $q_c<1$ is satisfied. For $q_c<1$, a seed black hole is always formed first, and then, it grows as the ambient fluid elements accrete onto it. We also find that the time evolution of the relation between angular momentum and mass enclosed in the seed black hole can be approximately determined from the initial profiles of the density and the specific angular momentum.

The Misner and Sharp approach to the study of gravitational collapse is extended to the dissipative case in, both, the streaming out and the diffusion approximations. The role of different terms in the dynamical equation are analyzed in detail. The dynamical equation is then coupled to a causal transport equation in the context of Israel-Stewart theory. The decreasing of the inertial mass density of the fluid, by a factor which depends on its internal thermodynamics state, is reobtained, at any time scale. In accordance with the equivalence principle, the same decreasing factor is obtained for the gravitational force term. Prospective applications of this result to some astrophysical scenarios are discussed.

We consider the Einstein-Yang-Mills Lagrangian in a $(4+n)$-dimensional space-time. Assuming the matter and metric fields to be independent of the $n$ extra coordinates, a spherical symmetric Ansatz for the fields leads to a set of coupled ordinary differential equations. If we assume the metric to be diagonal, we find that either $n-1$ of the gauge potentials associated with the $n$ extra dimensions must vanish or the solutions are embedded abelian solutions. These latter are the Einstein-Maxwell-dilaton solutions in $(4+n)$ dimensions. We present generic solutions of the effective 4-dimensional Einstein-Yang-Mills-Higgs-dilaton model, which possesses $n$ Higgs triplets coupled in a specific way to $n$ independent dilaton fields. These solutions are the abelian Einstein-Maxwell- dilaton solutions and analytic nonabelian solutions, which have diverging Higgs fields. In addition, we construct numerically asymptotically flat and finite energy solutions for $n=2$. If we choose the metric to have off-diagonal components, generic solutions of the full model are possible. We present the numerical solutions for the case $n=2$.

Recent claims point out that possible violations of Lorentz symmetry appearing in some semiclassical models of extended matter dynamics motivated by loop quantum gravity can be removed by a different choice of phase-space variables. In this note we show that such alternative is inconsistent with (i) the choice of variables in the regularized underlying quantum theory from which the effective theories are derived and (ii) the application of the correspondence principle. A consistent choice will violate standard Lorentz invariance, with the exception of trivial zero Planck scale corrections which are allowed by the analysis. Thus, for nontrivial corrections, to preserve a relativity principle in these models, the linear realization of Lorentz symmetry should be extended or superseded.

Analytic solutions are presented which describe the construction of a traversable wormhole from a Schwarzschild black hole, and the enlargement of such a wormhole, in Einstein gravity. The matter model is pure radiation which may have negative-energy density (phantom or ghost radiation) and the idealization of impulsive radiation (infinitesimally thin null shells) is employed.

We analyze the limits on resonant particle production during inflation based upon the power spectrum of fluctuations in matter and the cosmic microwave background. We show that such a model is consistent with features observed in the matter power spectrum deduced from galaxy surveys and damped Lyman-$\alpha$ systems at high redshift. It also provides an alternative explanation for the excess power observed in the power spectrum of the cosmic microwave background fluctuations in the range of $1000<l<3500$. For our best-fit models, epochs of resonant particle creation reenter the horizon at wave numbers of $k_{*}\sim 0.4$ and/or $0.2$ ($h{\mathrm{M}\mathrm{p}\mathrm{c}}^{-1}$). The amplitude and location of these features correspond to the creation of fermion species of mass $\sim 1-2{\mathrm{M}}_{pl}$ during inflation with a coupling constant between the inflaton field and the created fermion species of near unity. Although the evidence is marginal, if this interpretation is correct, this could be one of the first observational hints of new physics at the Planck-scale.

We investigate the motion of a wave packet of a charged scalar particle linearly accelerated by a static potential in quantum electrodynamics. We calculate the expectation value of the position of the charged particle after the acceleration to first order in the fine structure constant in the $\hslash \to 0$ limit. We find that the change in the expectation value of the position (the position shift) due to radiation reaction agrees exactly with the result obtained using the Lorentz-Dirac force in classical electrodynamics. We also point out that the one-loop correction to the potential may contribute to the position change in this limit.

We discuss the possibility of detecting a Higgs boson in electron-positron collider experiments if large extra dimensions are realized in nature. In such a case, the Higgs boson can decay invisibly by oscillating into a graviscalar Kaluza-Klein tower. We show that the search for such a Higgs boson at an $e^{+}{e}^{-}$ linear collider entails more complications than are usually thought of in relation to an invisibly decaying Higgs boson. The main sources of such complications are due to the simultaneous presence of a continuum graviton production and the broadening of the Higgs peak. We discuss possible ways of overcoming such difficulties and conclude that the detection of such a Higgs boson might still be a problem beyond the mass range of 250-300 GeV.

We consider the phenomenology of a fermiophobic Higgs boson ($h_f$) at the Large Hadron Collider (LHC) and a $e^{+}{e}^{-}$ linear collider (LC). At both machines the standard production mechanisms which rely on the coupling $h_{f}VV$ ($V=W^{\pm },Z$) can be very suppressed at large $\tan \beta$. In such cases the complementary channels $pp\to H^{\pm }{h}_f,A^0{h}_f$ and $e^{+}{e}^{-}\to A^0{h}_f$ offer promising cross sections. Together with the potentially large branching ratios for $H^{\pm }\to h_f{W}^{*}$ and $A^0\to h_f{Z}^{*}$, these mechanisms would give rise to double $h_f$ production, leading to signatures of $\gamma \gamma \gamma \gamma$, $\gamma \gamma VV$ and $VVVV$.

The baryonic potential in the framework of the $SU(3)$ random vortex world-surface model is evaluated for a variety of static color source geometries. For comparison, carefully taking into consideration the string tension anisotropy engendered by the hypercubic lattice description, also the $\Delta$ and Y law predictions for the baryonic potential are given. Only the Y law predictions are consistent with the baryonic potentials measured.

We study a parity-conserving single-spin beam asymmetry of elastic electron-proton scattering induced by an absorptive part of the two-photon exchange amplitude. It is demonstrated that excitation of inelastic hadronic intermediate states by the consecutive exchange of two photons leads to logarithmic and double-logarithmic enhancement due to contributions of hard collinear quasireal photons. The asymmetry at small electron scattering angles is expressed in terms of the total photoproduction cross section on the proton and is predicted to reach the magnitude of 20–30 ppm. At these conditions and fixed 4-momentum transfers, the asymmetry is rising logarithmically with increasing electron beam energy, following the high-energy diffractive behavior of total photoproduction cross section on the proton.

We study the time evolution of the one-loop diagram in Sen’s rolling tachyon background. We find that at least in the long cylinder case they grow rapidly at late time, due to the exponential growth of the timelike oscillator terms in the boundary state. This can also be interpreted as the virtual open string pair creation in the decaying brane. This behavior indicates a breakdown of this rolling tachyon solution at some point during the evolution. We also discuss the closed string emission from this one-loop diagram, and the evolution of a one-loop diagram connecting a decaying brane to a stable brane, which is responsible for the physical open string creation on the stable brane.

In self-interacting scalar field theories kinetic expansion is an alternative way of calculating the generating functional for Green’s functions where the zeroth order non-Gaussian path integral becomes diagonal in $x$-space and reduces to the product of an ordinary integral at each point which can be evaluated exactly. We discuss how to deal with such functional integrals and propose a new perturbative expansion scheme which combines the elements of the kinetic expansion with the usual perturbation theory techniques. It is then shown that, when the cutoff dependences of the bare parameters in the potential are chosen to have a well defined non-Gaussian path integral without the kinetic term, the theory becomes trivial in the continuum limit.

We determine the influence of a variation of the fundamental “constants” on the predicted helium abundance in Big Bang Nucleosynthesis. The analytic estimate is performed in two parts: the first step determines the dependence of the helium abundance on the nuclear physics parameters, while the second step relates those parameters to the fundamental couplings of particle physics. This procedure can incorporate in a flexible way the time variation of several couplings within a grand unified theory while keeping the nuclear physics computation separate from any GUT model dependence.

The cosmological evolution of a quintessencelike scalar field $\varphi$ coupled to matter and gauge fields leads to effective modifications of the coupling constants and particle masses over time. We analyze a class of models where the scalar field potential $V(\varphi )$ and the couplings to matter $B(\varphi )$ admit common extremum in $\varphi$, as in the Damour-Polyakov ansatz. We find that even for the simplest choices of potentials and $B(\varphi )$, the observational constraints on $\Delta \alpha /\alpha$ coming from quasar absorption spectra, the Oklo phenomenon and Big Bang nucleosynthesis provide complementary constraints on the parameters of the model. We show the evolutionary history of these models in some detail and describe the effects of a varying mass for dark matter.

In the scenario of electroweak baryogenesis we consider the dynamics of fermions with a spatially varying mass in the presence of a $CP$-violating bubble wall and a uniform magnetic field perpendicular to the wall. The relevant quantity for baryogenesis, $R_{R\to L}-R_{L\to R}$, is studied ($R_{R\to L}$ and $R_{L\to R}$ being the reflection coefficients for right-handed and left-handed chiral fermions, respectively).

A topologically finite universe, smaller than the observable horizon, will have circles-in-the-sky: pairs of circles around which the temperature fluctuations in the cosmic microwave background are correlated. The circles occur along the intersection of copies of the spherical surface of last scattering. For any observer moving with respect to the microwave background, the circles will be deformed into ovals. The ovals will also be displaced relative to the direction they appear in a comoving frame. The displacement is the larger of the two effects, being proportional to the velocity. For the Earth’s motion, the effect is on the order of 0.14° at the very worst. This can affect all pattern-based searches for the topology of the universe. In particular, although the deviation is too small to impact the search for circles in the Wilkinson microwave anisotropy probe (WMAP) data, higher-resolution searches for circle pairs will need to compensate for this effect.