We propose a two-zero-texture general Zee model, compatible with the large mixing angle Mikheyev-Smirnov-Wolfenstein solution. The washing out of the baryon number does not occur in this model for an adequate parameter range. We check the consistency of a model with the constraints coming from flavor changing neutral current processes, the recent cosmic microwave background observation, and the Z-burst scenario.

Results are presented on $J/\psi$ radiative decays to $K^{+}{K}^{-}$ and $K_S^0{K}_S^0$ based on a sample of 58M $J/\psi$ events taken with the BES II detector. A partial wave analysis is carried out using the relativistic covariant tensor amplitude method in the 1–2 GeV mass range. There is conspicuous production due to the $f_2^{\prime }\mathrm{}\left(1525\right)\mathrm{}$ and $f_0\mathrm{}\left(1710\right).$ The latter peaks at a mass of $1740\pm 4_{-25}^{+10\mathrm{}}\mathrm{MeV}$ with a width of ${166}_{-8-10}^{+5+15\mathrm{}}\mathrm{MeV}.$ Spin 0 is strongly preferred over spin 2. For the $f_2^{\prime }\mathrm{}\left(1525\right),$ the helicity amplitude ratios are determined to be $x^2=1.00\mathrm{}\pm {0.28}_{-0.36}^{+1.06\mathrm{}}$ and $y^2=0.44\mathrm{}\pm {0.08}_{-0.56}^{+0.10\mathrm{}}.$

In this work, the construction of supergravity duals to the noncommutative $\mathcal{N}=4\mathrm{}$ super Yang-Mills theory in the infinite momentum frame but with a constant momentum density is attempted. In the absence of noncommutativity, it has been known for some time that the previous ${\mathrm{AdS}}_5/{\mathrm{CFT}}_4$ correspondence should be replaced by the ${\mathrm{K}}_5/{\mathrm{CFT}}_4$ correspondence (with ${\mathrm{K}}_{\mathrm{}(p+2\mathrm{})\mathrm{}}$ denoting the generalized Kaigorodov spacetime) with a $\mathrm{pp}$ wave propagating on the Bogomol’nyi-Prasad-Sommerfield brane worldvolume. Interestingly enough, putting together the two additions, i.e., the introduction of noncommutativity and at the same time that of the $\mathrm{pp}$ wave along the brane worldvolume, leads to quite nontrivial consequences such as the emergence of “time-space” noncommutativity in addition to the “space-space” noncommutativity in the manifold on which the dual gauge theory is defined. Taking the gravity decoupling limit, it has been realized that, for small u, the solutions all reduce to ${\mathrm{K}}_5\times {\mathrm{S}}^5$ geometry, confirming our expectation that the IR dynamics of the dual gauge theory should be unaffected by the noncommutativity while, as $\overrightarrow{u}\infty ,$ the solutions start to deviate significantly from the ${\mathrm{K}}_5\times {\mathrm{S}}^5$ limit, indicating that the UV dynamics of dual gauge theory is heavily distorted by the effect of noncommutativity.

The boundary states for two dimensional anti–de Sitter $\left({\mathrm{AdS}}_2\right)$ Dirichlet-branes (D-branes) in Lorentzian ${\mathrm{AdS}}_3$ space-time are presented. ${\mathrm{AdS}}_2$ D-branes are algebraically defined by twisted Dirichlet boundary conditions and are located on twisted conjugacy classes of $\mathrm{SL}\mathrm{}(2,R).$ Using the free-field representation of symmetry currents in the $\mathrm{SL}\mathrm{}(2,R)\mathrm{}$ Wess-Zumino-Novikov-Witten model, the twisted Dirichlet gluing conditions among currents are translated to matching conditions among free fields and then to boundary conditions among the modes of free fields. The Ishibashi states are written as coherent states on ${\mathrm{AdS}}_3$ in the free field formalism and it is shown that twisted Dirichlet boundary conditions are satisfied on them. The tree-level amplitude of propagation of closed strings between two ${\mathrm{AdS}}_2$ D-branes is evaluated and by comparing it with the characters of $\mathrm{sl}^\mathrm{}(2,R)\mathrm{}$ Kac-Moody algebra it is shown that only states in the principal continuous series representation of $\mathrm{sl}^\mathrm{}(2,R)\mathrm{}$ Kac-Moody algebra contribute to the amplitude and thus they are the only ones that couple to ${\mathrm{AdS}}_2$ D-branes. The form of the character of $\mathrm{sl}^\mathrm{}(2,R)\mathrm{}$ principal continuous series and the boundary condition among the zero modes are used to determine the physical boundary states for ${\mathrm{AdS}}_2$ D-branes.

We present a toy model for five-dimensional heterotic M theory where bulk three-branes, originating in 11 dimensions from M five-branes, are modeled as kink solutions of a bulk scalar field theory. It is shown that the vacua of this defect model correspond to a class of topologically distinct M-theory compactifications. Topology change can then be analyzed by studying the time evolution of the defect model. In the context of a four-dimensional effective theory, we study in detail the simplest such process, that is, the time evolution of a kink and its collision with a boundary. We find that the kink is generically absorbed by the boundary thereby changing the boundary charge. This opens up the possibility of exploring the relation between more complicated defect configurations and the topology of brane-world models.

Quantum vacuum energy has been known to have observable consequences since 1948 when Casimir calculated the force of attraction between parallel uncharged plates, a phenomenon confirmed experimentally with ever increasing precision. Casimir himself suggested that a similar attractive self-stress existed for a conducting spherical shell, but Boyer obtained a repulsive stress. Other geometries and higher dimensions have been considered over the years. Local effects, and divergences associated with surfaces and edges were studied by several authors. Quite recently, Graham et al. have reexamined such calculations, using conventional techniques of perturbative quantum field theory to remove divergences, and have suggested that previous self-stress results may be suspect. Here we show that the examples considered in their work are misleading; in particular, it is well known that in two space dimensions a circular boundary has a divergence in the Casimir energy for massless fields, while for general spatial dimension D not equal to an even integer the corresponding Casimir energy arising from massless fields interior and exterior to a hyperspherical shell is finite. It has also long been recognized that the Casimir energy for massive fields is divergent for curved boundaries. These conclusions are reinforced by a calculation of the relevant leading Feynman diagram in D and in three dimensions. There is therefore no doubt of the validity of the conventional finite Casimir calculations.

We construct a seven-dimensional brane world in a slice of ${\mathrm{AdS}}_7,$ where the boundary matter content is fixed by the cancellation of anomalies. The seven-dimensional minimal $\mathcal{N}=2\mathrm{}$ gauged supergravity is compactified on the orbifold $S^1/Z_2,$ and the supersymmetric bulk-boundary Lagrangian is consistently derived for boundary vector and hypermultiplets up to fermionic bilinear terms. Anomaly cancellation then fixes the boundary gauge coupling in terms of the seven-dimensional Planck mass, and a topological mass parameter of the Chern-Simons term. In addition for gauge groups containing the standard model, anomaly cancellation restricts the gauge groups on the six-dimensional boundaries to be only one of the exceptional groups. There are also special values of the separation of the two boundaries, where the boundary couplings become singular, and lead to a possible phase transition in the boundary theory. Furthermore, by the AdS/CFT correspondence our brane world is dual to a six-dimensional conformal field theory, suggesting that our bulk theory describes the strong coupling dynamics of six-dimensional theories.

Direct photon production from a quark-gluon plasma (QGP) in thermal equilibrium is studied directly in real time. In contrast with the usual S-matrix calculations, the real time approach is valid for a QGP that formed and reached local thermal equilibrium a short time after a collision and of finite lifetime $(\sim 10–20\mathrm{fm}/c$ as expected at BNL RHIC or CERN LHC). We point out that during such a finite QGP lifetime the spectrum of emitted photons carries information on the initial state. There is an inherent ambiguity in separating the virtual from the observable photons during the transient evolution of the QGP. We propose a real time formulation to extract the photon yield which includes the initial stage of formation of the QGP parametrized by an effective time scale of formation ${\Gamma }^{-1}.$ This formulation coincides with the S-matrix approach in the infinite lifetime limit. It allows us to separate the virtual cloud as well as the observable photons emitted during the preequilibrium stage from the yield during the QGP lifetime. We find that the lowest order contribution $O\left({\alpha }_{\mathrm{em}}\right)$ which does not contribute to the S-matrix approach, is of the same order of or larger than the S-matrix contribution during the lifetime of the QGP for a typical formation time $\sim 1\mathrm{fm}/c.\mathrm{}$ The yield for momenta $\gtrsim 3\mathrm{GeV}/c$ features a power law fall-off $\sim T^3{\Gamma }^2{/k}^5$ and is larger than that obtained with the S-matrix for momenta $>~4\mathrm{GeV}/c.\mathrm{}$ We provide a comprehensive numerical comparison between the real time and S-matrix yields and study the dynamics of the build-up of the photon cloud and the different contributions to the radiative energy loss. The reliability of the current estimates on photon emission as well as theoretical uncertainties on the details of the initial state are discussed.

We study the light-front Schwinger model at finite temperature following the recent proposal of Alves, Das, and Perez. We show that the calculations are carried out efficiently by working with the full propagator for the fermion, which also avoids subtleties that arise with light-front regularizations. We demonstrate this with the calculation of the zero temperature anomaly. We show that temperature dependent corrections to the anomaly vanish, consistent with the results from the calculations in conventional quantization. The gauge self-energy is seen to have the expected nonanalytic behavior at finite temperature, but does not quite coincide with the conventional results. However, the two structures are exactly the same on shell. We show that the temperature does not modify the bound state equations and that the fermion condensate has the same behavior at finite temperature as that obtained in conventional quantization.

We perform numerical simulations of the critical gravitational collapse of a massive vector field. The result is that there are two critical solutions. One is equivalent to the Choptuik critical solution for a massless scalar field. The other is periodic.

In this paper it is shown that the entropy of the black hole horizon in Achúcarro-Ortiz spacetime, which is the most general two-dimensional black hole derived from the three-dimensional rotating Bañados-Teitelboim-Zanelli black hole, can be described by the Cardy-Verlinde formula. The latter is supposed to be an entropy formula of conformal field theory in any dimension.

We derive a new first-order formulation for Einstein’s equations which involves fewer unknowns than other first-order formulations that have been proposed. The new formulation is based on the $3+1$ decomposition with arbitrary lapse and shift. In the reduction to first-order form only eight particular combinations of the 18 first derivatives of the spatial metric are introduced. In the case of linearization about Minkowski space, the new formulation consists of a symmetric hyperbolic system in 14 unknowns, namely, the components of the extrinsic curvature perturbation and the eight new variables, from whose solution the metric perturbation can be computed by integration.

The occurrence of a big smash singularity which ends the universe in a finite time in the future is investigated in the context of superquintessence, i.e. dark energy with an effective equation of state parameter $w<\mathrm{}-1$ and $\mathrm{Ḣ}>0.\mathrm{}$ The simplest toy model of superquintessence based on a single nonminimally coupled scalar field exhibits big smash solutions which are attractors in phase space.

We propose a new scenario to simultaneously explain a large lepton asymmetry and a small baryon asymmetry. We consider a rolling scalar field and its derivative coupling to the lepton number current. The presence of an effective nonzero time derivative of the scalar field leads to CPT violation so that the lepton asymmetry can be generated even in thermal equilibrium as pointed out by Cohen and Kaplan. In this model, the lepton asymmetry varies with time. In particular, we consider the case where it grows with time. The final lepton asymmetry is determined by the decoupling of the lepton number violating interaction and can be as large as order unity. On the other hand, if the decoupling takes place after the electroweak phase transition, a small baryon asymmetry is obtained from the small lepton asymmetry at that time through sphaleron effects. We construct a model in which a rolling scalar field is identified with a quintessence field.

We compute the perturbative expansion of the pressure of hot QCD to order $g^6\ln g$ in the presence of finite quark chemical potentials. In this process we evaluate all two- and three-loop vacuum diagrams of the theory at arbitrary T and $\mu$ and then use these results to analytically verify the outcome of an old order $g^4$ calculation of Freedman and McLerran for the zero-temperature pressure. The results for the pressure and the different quark number susceptibilities at high T are compared with recent lattice simulations showing excellent agreement especially for the chemical potential dependent part of the pressure.

In this work we will study the polarizations of both leptons $\left(\tau \right)$ in the decay channel $\overrightarrow{B}{K}^{*}{\tau }^{-}{\tau }^{+}.$ In the case of the dileptonic inclusive decay $\overrightarrow{B}{K}^{*}{\mathcal{l}}^{-}{\mathcal{l}}^{+},$ where apart from the polarization asymmetries of a single lepton $\mathcal{l},$ one can also observe the polarization asymmetries of both leptons simultaneously. If this sort of measurement is possible then we can have, apart from decay rate, forward backward asymmetry and the six single lepton polarization asymmetries (three each for ${\mathcal{l}}^{-}$ and ${\mathcal{l}}^{+}),$ nine more double polarization asymmetries. This will give us a very useful tool in more strict testing of the standard model (SM) and the physics beyond. We discuss the double polarization asymmetries of the $\tau$ leptons in the decay mode $\overrightarrow{B}{K}^{*}{\tau }^{-}{\tau }^{+}$ within the SM and the minimal supersymmetric extension of it.

We study the effect of supersymmetric phases on rare decays of leptons and on their magnetic and electric dipole moments. We consider the most general mass matrices for sleptons within the minimal supersymmetric standard model including left-right mixing, flavor mixing and complex phases. We show that the phases also affect $\mathrm{CP}$ even observables. Moreover, we demonstrate that contrary to common belief the phase of $\mu$ can be large even for slepton masses as small as 200 GeV provided the lepton flavor violating parameters are complex.

The details of two recent calculations of the two-loop bosonic corrections to the muon lifetime in the standard model are presented. The matching to the Fermi theory is discussed. Renormalization in the on-shell and the modified minimal subtraction schemes is studied and the transition between the schemes is shown to lead to identical results. High precision numerical methods are compared with the mass difference and large mass expansions.

We consider a brane scenario with a massive scalar field in the five-dimensional bulk. We study the scalar states that are localized on the brane, which is assumed to be a de Sitter brane. These localized scalar modes are massive in general, their effective four-dimensional mass depending on the mass of the five-dimensional scalar field, on the Hubble parameter in the brane and on the coupling between the brane tension and the bulk scalar field. We then introduce a purely four-dimensional approach based on an effective potential for the projection of the scalar field in the brane, and discuss its regime of validity. Finally, we explore the quasilocalized scalar states, which have a nonzero width that quantifies their probability of tunneling from the brane into the bulk.

We consider a D-brane coupled with gravity in type IIB supergravity on $S^5$ and derive the effective theory on the D-brane in two different ways: that is, holographic and geometrical projection methods. We find that the effective equations on the brane obtained by these methods coincide. The theory on the D-brane described by the Born-Infeld action is not like Einstein-Maxwell theory in the lower order of the gradient expansion; i.e., the Maxwell field does not appear in the theory. Thus a careful analysis and statement for cosmology on a self-gravitating D-brane should be demanded in realistic models.