We compute one-loop correlation functions for the fluctuations of an interface using a ${\phi }^4$ field theory model in $d=2\mathrm{}$ and $d=3\mathrm{}$ dimensions. We obtain them from Feynman diagrams drawn with a propagator that is the inverse of the Hamiltonian of a Pöschl-Teller problem. We derive an expression for the propagator in terms of elementary functions, show that it corresponds to the usual spectral sum, and use it to calculate quantities such as the surface tension and interface profile in two and three spatial dimensions. The three-dimensional quantities are rederived in a simple, unified manner, whereas those in two dimensions extend the existing literature, and are applicable to thin films. In addition, we compute the one-loop self-energy, which may be extracted from experiment or from Monte Carlo simulations. Our results may be applied in various scenarios, which include fluctuations around topological defects in cosmology, supersymmetric domain walls, $Z\left(N\right)\mathrm{}$ bubbles in QCD, domain walls in magnetic systems, interfaces separating Bose-Einstein condensates, and interfaces in binary liquid mixtures.

We study the time evolution of the distribution functions for hot and or degenerate gases of two flavors of Dirac neutrinos as a result of flavor mixing and dephasing. This is achieved by obtaining the time evolution of the flavor density matrix directly from quantum field theory at finite temperature and density. The time evolution features a rich hierarchy of scales which are widely separated in the nearly degenerate or relativistic cases and originate in interference phenomena between particle and antiparticle states. In the degenerate case the flavor asymmetry $\Delta N\left(t\right)\mathrm{}$ relaxes to the asymptotic limit $\Delta N\left(\infty \right)=\Delta N\left(0\right)\mathrm{}{\cos }^2\left(2\mathrm{}\theta \right)$ via dephasing resulting from the oscillations between flavor modes that are not Pauli blocked, with a power law $1/t$ for $t>\mathrm{}{t}_s\approx {2k}_F/\Delta M^2.$ $k_F$ is the largest of the Fermi momenta. The distribution function for flavor neutrinos and antineutrinos as well as off-diagonal densities are obtained. Flavor particle-antiparticle pairs are produced by mixing and oscillations with typical momentum $k\sim \overline{M},$ the average mass of the neutrinos. An effective field theory description emerges on long time scales in which the Heisenberg operators obey a Bloch-type equation of motion valid in the relativistic and nearly degenerate cases. We find the nonequilibrium propagators and correlation functions in this effective theory and discuss its regime of validity as well as the potential corrections.

This paper reports results from numerical simulations of the gravitational radiation emitted from non-rotating compact objects (both neutron stars and Schwarzschild black holes) as a result of the accretion of matter. We adopt a hybrid procedure in which we evolve numerically, and assuming axisymmetry, the linearized equations describing metric and fluid perturbations coupled to a fully nonlinear hydrodynamics code that calculates the motion of the accreting matter. The initial matter distribution, which is initially at rest, is shaped in the form of extended quadrupolar shells of either dust or obeying a perfect fluid equation of state. Self-gravity of the accreting layers of fluid is neglected, as well as radiation reaction effects. We use this idealized setup in order to understand the qualitative features appearing in the energy spectrum of the gravitational wave emission from compact stars or black holes, subject to accretion processes involving extended objects. A comparison for the case of point-like particles falling radially onto black holes is also provided. Our results show that, when the central object is a black hole, the spectrum is far from having only one clear, monochromatic peak at the frequency of the fundamental quasi-normal mode. On the contrary, it shows a complex pattern, with distinctive interference fringes produced by the interaction between the infalling matter and the underlying perturbed spacetime, in close agreement with results for point-like particles. Remarkably, most of the energy is emitted at frequencies lower than that of the fundamental mode of the black hole. Similar results are obtained for extended shells accreting onto neutron stars, but in this case the contribution of the stellar fundamental mode stands clearly in the energy spectrum. Our analysis illustrates that the gravitational wave signal driven by accretion onto compact objects is influenced more by the details and dynamics of the process, and the external distribution of matter, than by the quasi-normal mode structure of the central object. The gravitational waveforms from such accretion events appear to be much more complex than former simplified assumptions predicted.

We use null spherical (observational) coordinates to describe a class of inhomogeneous cosmological models. The proposed cosmological construction is based on the observer past null cone. A known difficulty in using inhomogeneous models is that the null geodesic equation is not integrable in general. Our choice of null coordinates solves the radial ingoing null geodesic by construction. Furthermore, we use an approach where the velocity field is uniquely calculated from the metric rather than put in by hand. Conveniently, this allows us to explore models in a noncomoving frame of reference. In this frame, we find that the velocity field has shear, acceleration, and expansion rate in general. We show that a comoving frame is not compatible with expanding perfect fluid models in the coordinates proposed and dust models are simply not possible. We describe the models in a noncomoving frame. We use the dust models in a noncomoving frame to outline a fitting procedure.

Starting from the recent classification of quotients of Freund-Rubin backgrounds in string theory of the type ${\mathrm{AdS}}_{p+1\mathrm{}}\times {\mathrm{S}}^q$ by one-parameter subgroups of isometries, we investigate the physical interpretation of the associated quotients by discrete cyclic subgroups. We establish which quotients have well-behaved causal structures, and of those containing closed timelike curves, which have interpretations as black holes. We explain the relation to previous investigations of quotients of asymptotically flat spacetimes and plane waves, of black holes in AdS spacetimes, and of Gödel-type universes.

Motivated by the need to control the exponential growth of constraint violations in numerical solutions of the Einstein evolution equations, two methods are studied here for controlling this growth in general hyperbolic evolution systems. The first method adjusts the evolution equations dynamically, by adding multiples of the constraints, in a way designed to minimize this growth. The second method imposes special constraint preserving boundary conditions on the incoming components of the dynamical fields. The efficacy of these methods is tested by using them to control the growth of constraints in fully dynamical 3D numerical solutions of a particular representation of the Maxwell equations that is subject to constraint violations. The constraint preserving boundary conditions are found to be much more effective than active constraint control in the case of this Maxwell system.

We study a toy model for phantom cosmology recently introduced in the literature and consisting of two oscillators, one of which carries negative kinetic energy. The results are compared with the exact phase space picture obtained for similar dynamical systems describing, respectively, a massive canonical scalar field conformally coupled to the spacetime curvature and a conformally coupled massive phantom. Finally, the dynamical system describing exactly a minimally coupled phantom is studied and compared with the toy model.

Using the recent WMAP determination of the baryon-to-photon ratio, ${10}^{10}\eta =6.14\mathrm{}$ to within a few percent, big bang nucleosynthesis (BBN) calculations can make relatively accurate predictions of the abundances of the light element isotopes which can be tested against observational abundance determinations. At this value of $\eta ,$ the ${}^7\mathrm{Li}$ abundance is predicted to be significantly higher than that observed in low metallicity halo dwarf stars. Among the possible resolutions to this discrepancy are (1) ${}^7\mathrm{Li}$ depletion in the atmosphere of stars, (2) systematic errors originating from the choice of stellar parameters—most notably the surface temperature, and (3) systematic errors in the nuclear cross sections used in the nucleosynthesis calculations. Here, we explore the last possibility, and focus on possible systematic errors in the ${}^3\mathrm{He}(\alpha ,\gamma {)}^7\mathrm{Be}$ reaction, which is the only important ${}^7\mathrm{Li}$ production channel in BBN. The absolute value of the cross section for this key reaction is known relatively poorly both experimentally and theoretically. The agreement between the standard solar model and solar neutrino data thus provides additional constraints on variations in the cross section ${(S}_{34}).\mathrm{}$ Using the standard solar model of Bahcall, and recent solar neutrino data, we can exclude systematic $S_{34}$ variations of the magnitude needed to resolve the BBN ${}^7\mathrm{Li}$ problem at the $\gtrsim 95\%$ C.L., or more strongly, depending on the Li observations used. Additional laboratory data on ${}^3\mathrm{He}(\alpha ,\gamma {)}^7\mathrm{Be}$ will sharpen our understanding of both BBN and solar neutrinos, particularly if care is taken in determining the absolute cross section and its uncertainties. Nevertheless, it is already clear that this “nuclear fix” to the ${}^7\mathrm{Li}$ BBN problem is unlikely; other possible solutions are briefly discussed.

We discuss the hypothesis that cosmological baryon asymmetry and entropy were produced in the early Universe by a phase transition of the scalar fields in the framework of the spontaneous baryogenesis scenario. We show that the annihilation of the matter-antimatter clouds during the cosmological hydrogen recombination could distort the CMB anisotropies and polarization by delaying the recombination. After recombination the annihilation of the antibaryonic clouds (ABCs) and baryonic matter can produce peaklike reionization at the high redshifts before quasar and early galaxy formation. We discuss the constraints on the parameters of the spontaneous baryogenesis scenario by the recent WMAP CMB anisotropy and polarization data and on possible manifestation of the antimatter clouds in the upcoming Planck data.

We point out that the so-called soft leptogenesis can occur at the TeV scale if the B term is generated through radiative corrections which involve two-loop diagrams with the gaugino exchange. This mechanism requires the nontrivial CP phase, $\mathrm{Im}{(Am}_{1/2}^{*})\ne 0,$ and can naturally explain the observed baryon asymmetry of the Universe associated with the TeV scale seesaw mechanism. Such a low scale leptogenesis would be a promising option in view of the tight upper limit on the reheat temperature avoiding the gravitino problem in supergravity models.

The heat kernel expansion for field theory at finite temperature is constructed. It is based on the imaginary time formalism and applies to generic Klein-Gordon operators in flat space-time. Full gauge invariance is manifest at each order of the expansion and the Polyakov loop plays an important role at any temperature. The expansion is explicitly worked out up to operators of dimension 6 included. The method is then applied to compute the one-loop effective action of QCD at finite temperature with massless quarks. The calculation is carried out within the background field method in the $\overline{\mathrm{MS}}$ scheme up to dimension-6 operators. Further, the action of the dimensionally reduced effective theory at high temperature is also computed to the same order. Existing calculations are reproduced and new results are obtained in the quark sector for which only partial results existed up to dimension 6.

Recently, realistic theories of electroweak symmetry breaking have been constructed in which the electroweak symmetry is broken by boundary conditions imposed at a boundary of higher dimensional spacetime. These theories have equivalent 4D dual descriptions, in which the electroweak symmetry is dynamically broken by nontrivial infrared dynamics of some gauge interaction, whose gauge coupling $\tilde{g}$ and size N satisfy $g^{2}N\gtrsim 16{\pi }^2.$ Such theories allow one to calculate electroweak radiative corrections, including the oblique parameters S, T and U, as long as $g^{2}N/16\mathrm{}{\pi }^2$ and N are sufficiently larger than unity. We study how the duality between the 4D and 5D theories manifests itself in the computation of various physical quantities. In particular, we calculate the electroweak oblique parameters in a warped 5D theory where the electroweak symmetry is broken by boundary conditions at the infrared brane. We show that the value of S obtained in the minimal theory exceeds the experimental bound if the theory is in a weakly coupled regime. This requires either an extension of the minimal model or departure from weak coupling. A particularly interesting scenario is obtained if the gauge couplings in the 5D theory take the largest possible values—the value suggested by naive dimensional analysis. We argue that such a theory can provide a potentially consistent picture for dynamical electroweak symmetry breaking: corrections to the electroweak observables are sufficiently small while realistic fermion masses are obtained without conflicting with bounds from flavor violation. The theory contains only the standard model quarks, leptons and gauge bosons below $\simeq 2\mathrm{TeV},$ except for a possible light scalar associated with the radius of the extra dimension. At $\simeq 2\mathrm{TeV}$ increasingly broad string resonances appear. An analysis of top-quark phenomenology and flavor violation is also presented, which is applicable to both the weakly coupled and strongly coupled cases.

We investigate the decay mechanism in the $B^{-}\to \phi \phi K^{-}$ decay with the $\phi \phi$ invariant mass below the charm threshold and in the neighborhood of the ${\eta }_c$ invariant mass region. Our approach is based on the use of the factorization model and the knowledge of matrix elements of the weak currents. For the B meson weak transition we apply the form factor formalism, while for the light mesons we use effective weak and strong Lagrangians. We find that the dominant contributions to the branching ratio come from the $\eta ,$ ${\eta }^{\prime }$ and $\eta \mathrm{}\left(1490\right)\mathrm{}$ pole terms of the penguin operators in the decay chains $B^{-}\to \eta ({\eta }^{\prime },\eta \mathrm{}(1490\left)\mathrm{}\right)K^{-}\to \phi \phi K^{-}.$ Our prediction for the branching ratio is in agreement with the Belle Collaboration’s result.

In this paper we consider the possibility of the neutrino mass varying during the evolution of the Universe and study its implications on leptogenesis. Specifically, we take the minimal seesaw model of neutrino masses and introduce a coupling between the right-handed neutrinos and the dark energy scalar field, the quintessence. In our model, the right-handed neutrino masses change as the quintessence evolves. We then examine in detail the parameter space of this model allowed by the observed baryon number asymmetry. Our results show that it is possible to lower the reheating temperature in this scenario in comparison with the case that the neutrino masses are unchanged, which helps solve the gravitino problem. Furthermore, a degenerate neutrino mass pattern with $m_i$ larger than the upper limit given in the minimal leptogenesis scenario is permitted.

Recent measurement of time dependent asymmetries in $\overrightarrow{B}\phi K$ are indicative of a new source of CP violation. We examine squark mixing in supersymmetry as this new source, and using a QCD improved factorization method to describe $\overrightarrow{B}\phi K$ decay we find the allowed range of parameter space for $\rho$ and $\psi ,$ the magnitude and phase of the down type LR $\mathrm{}\left(\mathrm{RL}\right)\mathrm{}$ squark mixing parameter ${\delta }_{\mathrm{LR}\left(\mathrm{RL}\right)\mathrm{}}^{\mathrm{bs}}.$ We then study $\overrightarrow{B}\phi K^{*}$ and calculate the expected CP asymmetries in the same range of parameter space. We find that this asymmetry is in the range 15%–20% for an acceptable value of the $\overrightarrow{B}\phi K^{*}$ branching ratio. We also predict the helicity dependent CP asymmetries in the same parameter space.

We report the results of a study of charged B decays to the $D^{\pm }{\pi }^{\mp }{\pi }^{\mp }$ and $D^{*\pm }{\pi }^{\mp }{\pi }^{\mp }$ final states using complete $D^{\left(*\right)}$ reconstruction. The contributions of two-body $\overrightarrow{B}{D}^{**}\pi$ decays with narrow $\mathrm{}(j=3/2\mathrm{})\mathrm{}$ and broad $\mathrm{}(j=1/2\mathrm{})\mathrm{}$ $D^{**}$ states have been determined and the masses and widths of four $D^{**}$ states have been measured. This is the first observation of the broad P-wave $D_0^{*0}$ and $D{\prime }_1^0$ mesons. The analysis is based on a data sample of 65 million $B\overline{B}$ pairs collected in the Belle experiment.

The general solution for a stationary circularly symmetric metric ${\mathrm{ds}}^2=-{N\left(r\right)\mathrm{}}^2{\mathrm{dt}}^2{+dr}^2{/F\left(r\right)\mathrm{}}^2{+r}^2\left[d\phi -{J/(2r}^2\right)dt{]}^2,$ coupled to a rigidly rotating perfect fluid and a cosmological constant, is determined through an arbitrarily given function $N\left(r\right),$ which allows the evaluation of the structural function $F\left(r\right),$ the energy density, and the isotropic pressure. The interior solution with a constant energy density can be matched to the BTZ black hole.

We consider two approaches to evading paradoxes in quantum mechanics with closed timelike curves. In a model similar to Politzer’s, assuming pure states and using path integrals, we show that the problems of paradoxes and of unitarity violation are related; preserving unitarity avoids paradoxes by modifying the time evolution so that improbable events become certain. Deutsch has argued, using the density matrix, that paradoxes do not occur in the “many worlds interpretation.” We find that in this approach account must be taken of the resolution time of the device that detects objects emerging from a wormhole or other time machine. When this is done one finds that this approach is viable only if macroscopic objects traversing a wormhole interact with it so strongly that they are broken into microscopic fragments.

Astronomical observations have established that extremely compact, massive objects are common in the Universe. It is generally accepted that these objects are, in all likelihood, black holes. As observational technology has improved, it has become possible to test this hypothesis in ever greater detail. In particular, it is or will be possible to measure the properties of orbits deep in the strong field of a black hole candidate (using x-ray timing or future gravitational-wave measurements) and to test whether they have the characteristics of black hole orbits in general relativity. Past work has shown that, in principle, such measurements can be used to map the spacetime of a massive compact object, testing in particular whether the object’s multipolar structure satisfies the rather strict constraints imposed by the black hole hypothesis. Performing such a test in practice requires that we be able to compare against objects with the “wrong” multipole structure. In this paper, we present tools for constructing the spacetimes of bumpy black holes: objects that are almost black holes, but that have some multipoles with the wrong value. In this first analysis, we focus on objects with no angular momentum. Generalization to bumpy Kerr black holes should be straightforward, albeit labor intensive. Our construction has two particularly desirable properties. First, the spacetimes which we present are good deep into the strong field of the object—we do not use a “large r” expansion (except to make contact with weak field intuition). Second, our spacetimes reduce to the exact black hole spacetimes of general relativity in a natural way, by dialing the “bumpiness” of the black hole to zero. We propose that bumpy black holes can be used as the foundation for a null experiment: if black hole candidates are indeed the black holes of general relativity, their bumpiness should be zero. By comparing the properties of orbits in a bumpy spacetime with those measured from an astrophysical source, observations should be able to test this hypothesis, stringently testing whether they are in fact the black holes of general relativity.

The local isometry between black holes and colliding plane waves is employed to derive new colliding wave solutions in the Einstein-Maxwell-dilaton-axion theory. The technique is applied to the asymptotically nonflat linear dilaton black holes. We obtain two new metrics which we label (from the language of black holes) as Kerr and Newman-Unti-Tamburino (NUT) types. The NUT type turns out to be type D while the Kerr type belongs to the general class. Both types share the common feature that, instead of an all encompassing generic singularity, Cauchy horizons develop in the process of collision.