The tiny neutrino masses measured in neutrino oscillation experiments can be naturally explained via a supersymmetric seesaw mechanism. If supersymmetry breaking is mediated by gravity, such seesaw models may predict observable lepton flavor violating effects. In this work, we investigate the lepton flavor violating process $\overrightarrow{\mu }e\gamma$ in supersymmetric seesaw models with a “lopsided” charged lepton mass matrix. Constraints set by the muon anomalous magnetic moment are taken into account. We find that such models generally predict a branching ratio for $\overrightarrow{\mu }e\gamma$ far above the current experimental limit. Thus this process strongly constrains models of this type. Such restrictions suggest a novel form for the charged lepton mass matrix, featuring a “lopsided” structure for elements between both the 2-3 and the 1-3 generations. This structure produces a very small 1-3 mixing and a large 1-2 mixing in the charged lepton sector, leading naturally to a small $\mathrm{Br}\left(\overrightarrow{\mu }e\gamma \right)$ and to the large mixing angle solution for the solar neutrino problem.

We consider the Wilson line pseudo Nambu-Goldstone bosons (PNGB) which arises in a ${U\left(1\right)\mathrm{}}^N$ gauge theory, abstracted from a latticized, periodically compactified extra dimension $U\left(1\right).$ Planck scale breaking of the PNGB’s global symmetry is suppressed, providing natural candidates for the axion and quintessence. We construct an explicit model in which the axion may be viewed as the fifth component of the ${U\left(1\right)\mathrm{}}_Y$ gauge field in a $1+4$ latticized periodically compactified extra dimension. We also construct a quintessence PNGB model where the ultralow mass arises from Planck-scale suppressed physics itself.

The Laplacian gauge is a nonperturbative gauge fixing that reduces to the Landau gauge in the asymptotic limit. Like the Landau gauge, it respects Lorentz invariance, but it is free of Gribov copies; the gauge fixing is unambiguous. In this paper we study the infrared behavior of the lattice gluon propagator in the Laplacian gauge by using a variety of lattices with spacings from $a=0.125\mathrm{}$ to 0.35 fm, to explore finite volume and discretization effects. Three different implementations of the Laplacian gauge are defined and compared. The Laplacian gauge propagator has already been claimed to be insensitive to finite volume effects and this is tested on lattices with large volumes.

Recent years have seen extensive applications of the Nambu–Jona-Lasinio (NJL) model in the study of matter at high density. There is a good deal of interest in the predictions of diquark condensation and color superconductivity, with suggested applications to the study of the properties of neutron stars. As the researchers in this field note, the NJL model does not describe confinement, so that one is limited to the study of the deconfined phase, which may set in at several times nuclear matter density. Recently, we have extended the NJL model to include a covariant confinement model. Our model may be used to study the properties of the full range of light mesons, including their radial excitations, in the 1–3 GeV energy domain. Most recently we have used our extended model to provide an excellent fit to the properties of the $\eta \mathrm{}\left(547\right)\mathrm{}$ and ${\eta }^{\prime }\mathrm{}\left(958\right)\mathrm{}$ mesons and their radial excitations. The mixing angles and decay constants are given successfully in our model. In the present work our goal is to include a phenomenological model of deconfinement at finite matter density, using some analogy to what is known concerning “string breaking” and deconfinement at finite temperature. Various models may be used, but for this work we choose a specific model for the density dependence of the parameters of our confining interaction. We perform relativistic random-phase-approximation (RPA) calculations of the properties of the π(138), $K\left(495\right),$ $f_0\mathrm{}\left(980\right),$ $a_0\mathrm{}\left(980\right),$ and $K_0^{*}\mathrm{}\left(1430\right)\mathrm{}$ mesons and their radial excitations. In the model chosen for this work, there are no mesonic states beyond about $2{\rho }_{\mathrm{NM}},$ where ${\rho }_{\mathrm{NM}}$ is the density of nuclear matter. (The density for deconfinement in our model may be moved to higher values by the change of one of the parameters of the model.) This inability of the model to support bound hadronic states at large values of the density is taken as a signal of deconfinement. In addition to the density dependence of the confining interaction, we use the density-dependent quark mass values obtained in either the SU(2)- or SU(3)-flavor versions of the NJL model. We stress that other assumptions for the density dependence of the confinement potential, other than that used in this work, may be considered in future work, particularly if we are able to obtain further insight in the dynamics of deconfinement at finite matter density.

We study the radiative decay of ${\rm Y}$ into a scalar glueball $\overrightarrow{{\rm Y}}\gamma G_s$ using QCD factorization. We find that for this process the nonperturbative effects can be factorized into a matrix element well defined in nonrelativistic QCD (NRQCD) and the gluon distribution amplitude. The same NRQCD matrix element appears also in the leptonic decay of ${\rm Y}$ and therefore can be determined from data. In the asymptotic limit the gluon distribution amplitude is known up to a normalization constant. Using a QCD sum-rule calculation for the normalization constant, we obtain $\mathrm{Br}\left(\overrightarrow{{\rm Y}}\gamma G_s\right)$ to be in the range $(1\mathrm{}–2)\times {10}^{-3}.$ We also discuss some of the implications for $\overrightarrow{{\rm Y}}\gamma f_i$ decays. Near future data from CLEO-III can provide crucial information about scalar glueball properties.

In semileptonic decays of spin-1/2 baryons containing heavy quarks up to six charge assignments for the baryons and lepton are possible. We show that the radiative corrections to four of these possibilities can be directly obtained from the final results of the two possibilities previously studied. There is no need to recalculate integrals over virtual or real photon momentum or any traces.

The interaction of Reggeized gluons in multicolor QCD is considered in the Baxter-Sklyanin representation, where the wave function is expressed as a product of Baxter functions $Q\left(\lambda \right)$ and a pseudovacuum state. We find n solutions of the Baxter equation for a composite state of n gluons with poles of rank r in the upper $\lambda$ semiplane and of rank $n-1-r$ in the lower $\lambda$ semiplane $(0\mathrm{}<~r<~n-1).$ These solutions are related by $n-2$ linear equations with coefficients depending on $\coth \left(\pi \lambda \right).\mathrm{}$ The poles cancel in the wave-function bilinear combination of holomorphic and antiholomorphic Baxter functions, guaranteeing its normalizability. The quantization of the intercepts of the corresponding Regge singularities appears as a result of the physical requirements that the holomorphic energies for all solutions of the Baxter equation are the same and the total energies, calculated around two singularities $\lambda ,{\lambda }^{*}\to \pm i,$ coincide. It results in simple properties of the zeros of the Baxter functions. For illustration, we calculate the parameters of the Reggeon states constructed from three and four gluons. For the odderon, the ground state has conformal spin $|m-\tilde{m}|=1\mathrm{}$ and its intercept equals unity. The ground state of four Reggeized gluons possesses conformal spin $2$ and its intercept turns out to be higher than that for the BFKL Pomeron. We calculate the anomalous dimensions of the corresponding operators for arbitrary ${\alpha }_s/\omega .$

Assuming that $\mathrm{CPT}$ is violated in the neutrino sector seems to be a viable alternative to sterile neutrinos when it comes to reconciling the LSND anomaly with the remainder of the neutrino data. There are different (distinguishable) ways of incorporating $\mathrm{CPT}$ violation into the standard model, including postulating $m\ne \overline{m}.$ Here, I investigate the possibility of introducing $\mathrm{CPT}$ violation via Lorentz-invariance violating effective operators (“ether” potentials) which modify neutrino oscillation patterns such as ordinary matter effects. I argue that, within a simplified two-flavor-like oscillation analysis and restricting the analysis to the lowest order Lorentz-invariance violating operators only, one cannot solve the solar neutrino puzzle and LSND anomaly while still respecting constraints imposed by other neutrino experiments, and comment on whether significant improvements should be expected from a three-flavor analysis. If one turns the picture upside down, some of the most severe constraints on such $\mathrm{CPT}$ violating terms can already be obtained from the current neutrino data, while much more severe constraints can arise from future neutrino oscillation experiments.

We study a flavor-changing top-pion production process $e^{+}{e}^{-}\to t\overline{c}{\Pi }_t^0$ in the top-color-assisted technicolor (TC2) model. The studies show that, with the high center of mass energy in the DESY TESLA collider, the production cross section of $e^{+}{e}^{-}\to t\overline{c}{\Pi }_t^0$ is at the order of magnitude 0.1 fb in most parameter regions of the TC2 model and a few tens of events of a top-pion production can be produced each year. The resonance effect can enhance the cross section to a few fb when the top-pion mass is small. With a clean background, the top-pion events can possibly be detected at the TESLA collider. On the other hand, we find that there exists a narrow peak near $m_t-m_c$ in the top-pion–charm invariant mass distribution which could be clearly detected. Therefore, such a top-pion production process $e^{+}{e}^{-}\to t\overline{c}{\Pi }_t^0$ provides a unique chance to detect top-pion events and test the TC2 model.

We present the results of the first lattice QCD study of the strong coupling $g_{D^{*}D\pi }.$ From our simulations in the quenched approximation, we obtain $g_{D^{*}D\pi }=18.8\mathrm{}\pm {2.3}_{-2.0}^{+1.1\mathrm{}}$ and $g_c=0.67\mathrm{}\pm {0.08}_{-0.06}^{+0.04\mathrm{}}.$ Whereas previous theoretical studies gave different predictions, our result favors a large value for $g_c.$ It agrees very well with the recent experimental value by CLEO. $ĝ$ varies very little with the heavy mass and we find in the infinite mass limit $g_{\infty }=0.69\mathrm{}\left(18\right).$

A sizable rate of events where two pairs of b quarks are produced contemporarily is foreseen at the CERN LHC, as a consequence of the large parton luminosity. At very high energies both single and double parton scatterings contribute to the process, the latter mechanisms, although power suppressed, giving the dominant contribution to the integrated cross section.

In this paper, we study and try to find the constraint on the Cabibbo-Kobayashi-Maskawa (CKM) angle $\alpha$ from the experimental measurements of $\mathrm{CP}$ violation in $B_d^0\to {\pi }^{+}{\pi }^{-}$ decay, as reported very recently by the BaBar and Belle Collaborations. After considering the uncertainties of the data and the ratio r of the penguin to the tree amplitudes, we found that a strong constraint on both the CKM angle $\alpha$ and the strong phase $\delta$ can be obtained from the measured $\mathrm{CP}$ asymmetries $S_{\pi \pi }$ and $A_{\pi \pi }:$ (a) The ranges of $87°<~\alpha <~131°$ and $36°<~\delta <~144°$ are allowed by $1\sigma$ of the averaged data for $r=0.31;$ (b) for the Belle result alone, the limits on $\alpha$ and $\delta$ are $104°<~\alpha <~139°$ and $42°<~\delta <~138°$ for $0.32<~r<~0.41;$ and (c) an angle $\alpha$ larger than $90°$ is preferred.

We discuss the structure of the neutrino mass matrix as derived from a nonuniversal electroweak gauge interaction model. We discuss two interesting patterns of neutrino masses. The first pattern is hierarchal which fits the large mixing angle or low probability, low mass solution of solar neutrino data. The second pattern gives rise to an inverted mass spectrum which fits the currently not preferred small mixing angle solution. The mechanism for generating a light sterile neutrino mass is interesting and is briefly discussed.

$R$-parity violation in the supersymmetric standard model can be the source of neutrino masses and mixing. We analyze the neutrino mass matrix coming from either bilinear or trilinear R-parity violation and its collider signatures, assuming that the atmospheric and solar neutrino data are explained by three active neutrino oscillations. Taking the gauge mediated supersymmetry breaking mechanism, we show that the lightest neutralino decays well inside the detector and the model could be tested by observing its branching ratios in future colliders. In the bilinear model where only the small solar neutrino mixing angle can be accommodated, the relation ${10}^3\mathrm{BR}\left(\nu e^{\pm }{\tau }^{\mp }\right)\sim \mathrm{BR}\left(\nu {\mu }^{\pm }{\tau }^{\mp }\right)\approx \mathrm{BR}\left(\nu {\tau }^{\pm }{\tau }^{\mp }\right)$ serves as a robust test of the model. The large mixing angle solution can be realized in the trilinear model which predicts $\mathrm{BR}\left(\nu e^{\pm }{\tau }^{\mp }\right)\sim \mathrm{BR}\left(\nu {\mu }^{\pm }{\tau }^{\mp }\right)\sim \mathrm{BR}\left(\nu {\tau }^{\pm }{\tau }^{\mp }\right).\mathrm{}$ In either case, the relation $\mathrm{BR}\mathrm{}\left(\mathrm{ejj}\right)\mathrm{}\ll \mathrm{BR}\left(\mu jj\right)\sim \mathrm{BR}\left(\tau jj\right)$ should hold to be consistent with the atmospheric neutrino and CHOOZ experiments.

We consider “bubbles of nothing” constructed by analytically continuing black hole solutions in anti–de Sitter space. These provide interesting examples of smooth time-dependent backgrounds which can be studied through the AdS/CFT correspondence. Our examples include bubbles constructed from Schwarzschild-AdS, Kerr-AdS and Reissner-Nordström AdS. The Schwarzschild bubble is dual to Yang-Mills theory on three-dimensional de Sitter space times a circle. We construct the boundary stress tensor of the bubble spacetime and relate it to the properties of field theory on de Sitter space.

We show that any conformal field theory in d-dimensional Minkowski space, in a phase with spontaneously broken conformal symmetry and with the dilaton among its fields, can be rewritten in terms of the static gauge $\left(d-1\right)$-brane on ${\mathrm{AdS}}_{\mathrm{}(d+1\mathrm{})\mathrm{}}$ by means of an invertible change of variables. This nonlinear holographic transformation maps the Minkowski space coordinates onto the brane worldvolume ones and the dilaton onto the transverse AdS brane coordinate. One of the consequences of the existence of this map is that any $(d-1+m)$-brane worldvolume action on ${\mathrm{AdS}}_{\mathrm{}(d+1\mathrm{})\mathrm{}}\times X^m$ (with $X^m$ standing for the sphere $S^m$ or more complicated curved manifold) admits an equivalent description in Minkowski space as a nonlinear and higher-derivative extension of some conventional conformal field theory action, with the conformal group being realized in a standard way. The holographic transformation explicitly relates the standard realization of the conformal group to its field-dependent nonlinear realization as the isometry group of the brane ${\mathrm{AdS}}_{\mathrm{}(d+1\mathrm{})\mathrm{}}$ background. Some possible implications of this transformation, in particular for the study of the quantum effective action of $\mathcal{N}=4\mathrm{}$ super-Yang-Mills theory in the context of AdS/CFT correspondence, are briefly discussed.