The dynamical behavior of traversable wormholes and black holes under impulsive radiation is studied in an exactly soluble dilaton gravity model. Simple solutions are presented where a traversable wormhole is constructed from a black hole, or the throat of a wormhole is stably enlarged or reduced. These solutions illustrate the basic operating principles needed to construct similar analytic solutions in full Einstein gravity.

Three-dimensional gravity with a minimally coupled self-interacting scalar is considered. The falloff of the fields at infinity is assumed to be slower than that of a localized distribution of matter in the presence of a negative cosmological constant. However, the asymptotic symmetry group remains to be the conformal group. The counterterm Lagrangian needed to render the action finite is found by demanding that the action attain an extremum for the boundary conditions implied by the above falloff of the fields at infinity. These counterterms explicitly depend on the scalar field. As a consequence, the Brown-York stress-energy tensor acquires a nontrivial contribution from the matter sector. Static circularly symmetric solutions with a regular scalar field are explored for a one-parameter family of potentials. Their masses are computed via the Brown-York quasilocal stress-energy tensor, and they coincide with the values obtained from the Hamiltonian approach. The thermal behavior, including the transition between different configurations, is analyzed, and it is found that the scalar black hole can decay into the Bañados-Teitelboim-Zanelli solution irrespective of the horizon radius. It is also shown that the AdS conformal field theory correspondence yields the same central charge as for pure gravity.

We compute the Euclidean actions of a d-dimensional charged rotating black brane both in the canonical and the grand-canonical ensemble through the use of the counterterms renormalization method, and show that the logarithmic divergencies associated with the Weyl anomalies and matter field vanish. We obtain a Smarr-type formula for the mass as a function of the entropy, the angular momenta, and the electric charge, and show that these quantities satisfy the first law of thermodynamics. Using the conserved quantities and the Euclidean actions, we calculate the thermodynamics potentials of the system in terms of the temperature, angular velocities, and electric potential both in the canonical and grand-canonical ensembles. We also perform a stability analysis in these two ensembles, and show that the system is thermally stable. This is commensurate with the fact that there is no Hawking-Page phase transition for a black object with zero curvature horizon. Finally, we obtain the logarithmic correction of the entropy due to the thermal fluctuation around the equilibrium.

In this paper, we consider the gravitational radiation generated by the collision of highly relativistic particles with rotating Kerr black holes. We use the Sasaki-Nakamura formalism to compute the waveform, energy spectra, and total energy radiated during this process. We show that the gravitational spectrum for high-energy collisions has definite characteristic universal features, which are independent of the spin of the colliding objects. We also discuss the possible connections between these results and black-hole–black-hole collisions at the speed of light. Our results show that during the high-speed collision of a nonrotating hole with a rotating one, at most $35\%$ of the total energy can get converted into gravitational waves. This $35\%$ efficiency occurs only in the most optimistic situation, that of a zero impact parameter collision, along the equatorial plane, with an almost extreme Kerr black hole. In the general situation, the total gravitational energy radiated is expected to be much less, especially if the impact parameter increases. Thus, if one is able to produce black holes at the CERN Large Hadron Collider, at most $35\%$ of the partons’ energy should be emitted during the so-called balding phase. This energy will be missing, since we do not have gravitational wave detectors able to measure such amplitudes. The collision at the speed of light between one rotating black hole and a nonrotating one or two rotating black holes turns out to be the most efficient gravitational wave generator in the Universe.

We study a massless scalar field propagating in the background of a five-dimensional rotating black hole. We show that in the Myers-Perry metric describing such a black hole the massless field equation allows the separation of variables. The obtained angular equation is a generalization of the equation for spheroidal functions. The radial equation is similar to the radial Teukolsky equation for the 4-dimensional Kerr metric. We use these results to quantize the massless scalar field in the space-time of the 5-dimensional rotating black hole and to derive expressions for energy and angular momentum fluxes from such a black hole.

Standard derivations of “time-independent perturbation theory” of quantum mechanics cannot be applied to the general case where potentials are energy dependent or where the inverse free Green function is a nonlinear function of energy. Such derivations cannot be used, for example, in the context of relativistic quantum field theory. Here we solve this problem by providing a new, general formulation of perturbation theory for calculating the changes in the energy spectrum and wave function of bound states and resonances induced by perturbations to the Hamiltonian. Although our derivation is valid for energy-dependent potentials and is not restricted to inverse free Green functions that are linear in the energy, the expressions obtained for the energy and wave function corrections are compact, practical, and maximally similar to the ones of quantum mechanics. For the case of relativistic quantum field theory, our approach provides a direct covariant way of obtaining corrections to wave functions that are not in the center of mass frame.

We study dynamical mass generation in QED in $2+1$ dimensions using Hamiltonian lattice methods. We use staggered fermions, and perform simulations with explicit dynamical fermions in the chiral limit. We demonstrate that a recently developed method to reduce the fermion sign problem can successfully be applied to this problem. Our results are in agreement with both the strong coupling expansion and with the Euclidean lattice simulations.

The gauge problem of monopole dynamics is studied in $\mathrm{SU}\left(2\right)\mathrm{}$ lattice gauge theory. We study first the Abelian and monopole contributions to the static potential in four smooth gauges, i.e., the Laplacian Abelian, maximally Abelian Wilson loop, and L-type gauges in comparison with the maximally Abelian (MA) gauge. They all reproduce the string tension in good agreement with the $\mathrm{SU}\left(2\right)\mathrm{}$ string tension. The MA gauge is not the only choice of a good gauge which is suitable for the color confinement mechanism. Using an inverse Monte Carlo method and block spin transformation, we determine the effective monopole actions and the renormalization group (RG) flows of its coupling constants in various Abelian projection schemes. Every RG flow appears to converge to a unique curve which suggests gauge independence in the infrared region.

The final-state phases in $\overline{B}\to D\pi ,$ $D^{*}\pi ,$ and $D\rho$ decays appear to follow a pattern similar to those in $\overrightarrow{D}\overline{K}\pi ,$ $K^{*}\pi ,$ and $\overline{K}\rho$ decays. Each set of processes is characterized by three charge states but only two independent amplitudes, so the amplitudes form triangles in the complex plane. For the first two sets the triangles appear to have nonzero area, while for the $D\rho$ or $\overline{K}\rho$ decays the areas of the triangles are consistent with zero. Following an earlier discussion of this behavior for D decays, a similar analysis is performed for B decays, and the relative phases and magnitudes of contributing amplitudes are determined. The significance of recent results on $B^0\to D^{\left(*\right)0\mathrm{}}{K}^{\left(*\right)0\mathrm{}}$ is noted. Open theoretical and experimental questions are indicated.

We discuss different QCD approaches to calculate the form factor $F^{{\gamma }^{*}\gamma \pi }{(Q}^2)$ of the ${\gamma }^{*}\overrightarrow{\gamma }{\pi }^0$ transition giving preference to the light-cone QCD sum rules (LCSR) approach as being the most adequate. In this context we revise the previous analysis of the CLEO experimental data on $F^{{\gamma }^{*}\gamma \pi }{(Q}^2)$ by Schmedding and Yakovlev. Special attention is paid to the sensitivity of the results to the (strong radiative) ${\alpha }_s$ corrections and to the value of the twist-four coupling ${\delta }^2.$ We present a full analysis of the CLEO data at the NLO level of LCSRs, focusing particular attention on the extraction of the relevant parameters to determine the pion distribution amplitude, i.e., the Gegenbauer coefficients $a_2,a_4.$ Our analysis confirms our previous results and also the main findings of Schmedding and Yakovlev: both the asymptotic as well as the Chernyak-Zhitnitsky pion distribution amplitudes are completely excluded by the CLEO data. A novelty of our approach is to use the CLEO data as a means of determining the value of the QCD vacuum nonlocality parameter ${\lambda }_q^2=〈\overline{q}{D}^{2}q〉/〈\overline{q}q〉=0.4\mathrm{}{\mathrm{}\mathrm{GeV}}^2,$ which specifies the average virtuality of the vacuum quarks.

We study the consequences of assuming that the mass scale ${\Delta }_{\odot }$ corresponding to the solar neutrino oscillations and mixing angle $U_{e3\mathrm{}}$ corresponding to the electron neutrino oscillation at CHOOZ are radiatively generated through the standard electroweak gauge interactions. All the leptonic mass matrices having zero ${\Delta }_{\odot }$ and $U_{e3\mathrm{}}$ at a high scale lead to a unique low energy value for the ${\Delta }_{\odot }$ which is determined by the (known) size of the radiative corrections, solar and the atmospheric mixing angle and the Majorana mass of the neutrino observed in neutrinoless double beta decay. This prediction leads to the following consequences. (i) The MSSM radiative corrections generate only the dark side of the solar neutrino solutions. (ii) The inverted mass hierarchy $(m,-m,0)$ at the high scale fails in generating the LMA solution but it can lead to the LOW or vacuum solutions. (iii) The ${\Delta }_{\odot }$ generated in models with maximal solar mixing at a high scale is zero to the lowest order in the radiative parameter. It tends to get suppressed as a result of this and lies in the vacuum region. We discuss specific textures which can lead to the LMA solution in the present framework and provide a gauge theoretical realization of this in the context of the seesaw model.

In an attempt to explain the latest experimental result about the branching ratio of $\overrightarrow{\omega }{\pi }^0{\pi }^0\gamma$ decay, we reexamine the mechanism of this decay in a phenomenological framework in which the contributions of vector meson dominance, chiral loops, $\sigma$-meson intermediate state amplitudes, and the effects of $\omega -\rho$ mixing are considered. We conclude that in order to obtain the experimental value of the branching ratio $B\left(\overrightarrow{\omega }{\pi }^0{\pi }^0\gamma \right)$ the $\sigma$-meson amplitude, which makes a substantial contribution, should be included in the reaction mechanism and the effects of $\omega -\rho$ mixing should be taken into account. We also estimate the coupling constant $g_{\omega \sigma \gamma }$ as $g_{\omega \sigma \gamma }=0.11,$ which is much smaller than the values suggested by light cone QCD sum rule calculations.

We study the radiative ${\rho }^0\to {\pi }^{+}{\pi }^{-}\gamma$ and ${\rho }^0\to {\pi }^0{\pi }^0\gamma$ decays and we calculate their branching ratios using a phenomenological approach by adding to the amplitude calculated within the framework of chiral perturbation theory and vector meson dominance the amplitude of $\sigma$-meson intermediate state. Our results for the branching ratios are in good agreement with the experimental values.

It has been argued that by removing a pressure gradient term in the continuity equation, it is possible to obtain, with a semiclassical formulation, the same expression for the density contrast growing mode, as obtained in a full relativistic treatment. In this context, we reinvestigate the evolution of perturbations in an expanding Newtonian universe with pressure, but we consider a general scenario in which the equation of state parameter is time dependent and the perturbations are not necessarily adiabatic. We verify that, in this case, the suggested modification of the continuity equation does not provide equivalence between the relativistic and Newtonian descriptions.

We show that the Ginsparg-Wilson (GW) relation can play an important role in defining chiral structures in finite noncommutative geometries. Employing the GW relation, we can prove the index theorem and construct topological invariants even if the system has only finite degrees of freedom. As an example, we consider a gauge theory on a fuzzy two-sphere and give an explicit construction of a noncommutative analogue of the GW relation, chirality operator, and the index theorem. The topological invariant is shown to coincide with the first Chern class in the commutative limit.

We construct matter field theories in a “theory space” that is fractal, and invariant under geometrical renormalization group (RG) transformations. We treat in detail complex scalars, and discuss issues related to fermions, chirality, and Yang-Mills gauge fields. In the continuum limit these models describe physics in a noninteger spatial dimension which appears above a RG invariant “compactification scale” M. The energy distribution of KK modes above M is controlled by an exponent in a scaling relation of the vacuum energy (Coleman-Weinberg potential), and corresponds to the dimensionality. For truncated-$s$-simplex lattices with coordination number s the spacetime dimensionality is $1+[3+2\ln \mathrm{}(s)/\ln \mathrm{}(s+2\mathrm{}\left)\mathrm{}\right].$ The computations in theory space involve subtleties, owing to the $1+3$ kinetic terms, yet the resulting dimensionalites are equivalent to thermal spin systems. Physical implications are discussed.

We uncover a method of calculation that proceeds at every step without fixing the gauge or specifying details of the regularization scheme. Results are obtained by iterated use of integration by parts and gauge invariance identities. The initial stages can even be computed diagrammatically. The method is formulated within the framework of an exact renormalization group for $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$ Yang-Mills gauge theory, incorporating an effective cutoff through a manifest spontaneously broken $\mathrm{SU}\left(N|N\right)$ gauge invariance. We demonstrate the technique with a compact calculation of the one-loop beta function, achieving a manifestly universal result, and without gauge fixing, for the first time at finite N.

We study through numerical simulation the spherical collapse of isothermal gas in Newtonian gravity. We observe a critical behavior which occurs at the threshold of gravitational instability leading to core formation. This was predicted in a previous work by two of the present authors. We describe it in detail in this work. For a given initial density profile, we find a critical temperature $T^{*},$ which is of the same order as the virial temperature of the initial configuration. For the exact critical temperature, the collapse converges to a self-similar form, the first member in Hunter’s family of self-similar solutions. For a temperature close to $T^{*},$ the collapse first approaches this critical solution. Later on, in the supercritical case $(T<\mathrm{}{T}^{*}),$ the collapse converges to another self-similar solution, which is called the Larson-Penston solution. In the subcritical case $(T>\mathrm{}{T}^{*}),$ the gas bounces and disperses to infinity. We find two scaling laws with respect to $|T-T^{*}|:$ one for the collapsed mass in the supercritical case and the other, which was not predicted before, for the maximum density reached before dispersal in the subcritical case. The value of the critical exponent is measured to be $\simeq 0.11$ in the supercritical case, which agrees well with the predicted value $\simeq \mathrm{0.10567.}$ These critical properties are quite similar to those observed in the collapse of a radiation fluid in general relativity. We study the response of the system to temperature fluctuation and discuss astrophysical implications for the interstellar medium structure and for the star formation process. Newtonian critical behavior is important not only because it provides a simple model for general relativity but also because it is relevant for astrophysical systems such as molecular clouds.

We study the flavor changing neutral Higgs boson decays that can be induced from genuine supersymmetric particles at the one-loop level and within the context of the minimal supersymmetric standard model. We consider all the possible flavor changing decay channels of the three neutral Higgs bosons into second and third generation quarks, and focus on the supersymmetric-QCD corrections from squark-gluino loops which are expected to provide the dominant contributions. We assume here the more general hypothesis for flavor mixing, where there is misalignment between the quark and squark sectors, leading to a flavor nondiagonal squark mass matrix. The form factors involved and the corresponding Higgs partial decay widths and branching ratios are computed both analytically and numerically, and their behavior with the parameters of the minimal supersymmetric standard model and with the squark mass mixing is analyzed in full detail. The large rates found are explained in terms of the nondecoupling behavior of these squark-gluino loop corrections in the scenario with very large supersymmetric mass parameters. Our results show that if these decays are seen in future colliders, they could provide clear indirect signals of supersymmetry.

A method of reconstruction of the top quarks produced in the process $e^{+}{e}^{-}\to t\overline{t}\to 6\mathrm{jets}$ at a linear collider (LC) is proposed. The approach does not involve a kinematic fit, as well as assumptions on the invariant masses of the dijets originating from the decays of W bosons and, therefore, the method is expected to be less sensitive to theoretical and experimental uncertainties on the top-mass measurement than traditional reconstruction methods. For the first time, the reconstruction of the top quarks is investigated using the full LC detector simulation after taking into account the background arising from QCD multijet production.