We discuss two cosmological issues in a generic gauge-mediated supersymmetry- (SUSY-)breaking model, namely, the Universe’s baryon asymmetry and the gravitino dark-matter density. We show that both problems can be simultaneously solved if there exist extra matter multiplets of a SUSY-invariant mass of the order of the “μ term,” as suggested in several realistic SUSY grand-unified theories. We propose an attractive scenario in which the observed baryon asymmetry is produced in a way totally independent of the reheating temperature of inflation without causing any cosmological gravitino problem. Furthermore, in a relatively wide parameter space, we can also explain the present mass density of cold dark matter by the thermal relics of the gravitinos without an adjustment of the reheating temperature of inflation. We point out that there is an interesting relation between the baryon asymmetry and the dark-matter density.

It has been widely believed that variability of the fine-structure constant $\alpha$ would imply detectable violations of the weak equivalence principle. This belief is not justified in general. It is put to rest here in the context of the general framework for $\alpha$ variability [J. D. Bekenstein, Phys. Rev. D 25, 1527 (1982)] in which the exponent of a scalar field plays the role of the permittivity and inverse permeability of the vacuum. The coupling of particles to the scalar field is necessarily such that the anomalous force acting on a charged particle by virtue of its mass’s dependence on the scalar field is canceled by terms modifying the usual Coulomb force. As a consequence a particle’s acceleration in external fields depends only on its charge to mass ratio, in accordance with the principle. And the center of mass acceleration of a composite object can be proved to be independent of the object’s internal constitution, as the weak equivalence principle requires. Likewise the widely employed assumption that the Coulomb energy of matter is the principal source of the scalar field proves wrong; Coulomb energy effectively cancels out in the continuum description of the scalar field’s dynamics. This cancellation resolves a cosmological conundrum: with Coulomb energy as the source of the scalar field, the framework would predict a decrease of $\alpha$ with cosmological expansion, whereas an increase is claimed to be observed. Because of the said cancellation, magnetic energy of cosmological baryonic matter is the main source of the scalar field. Consequently the expansion is accompanied by an increase in $\alpha ;$ for reasonable values of the framework’s sole parameter, this occurs at a rate consistent with the observers’ claims.

The paper is divided into two independent parts. The first one contains the main subject of the paper: we calculate the number of photons produced per unit energy in a strong rotating magnetic field. Two different processes are considered: production through electron-positron pairs annihilation and direct production from the vacuum. In the second part, we calculate the probability of creating a Dirac neutrino-antineutrino pair in the presence of the same rotating magnetic field.

Anisotropic neutrino emission during neutron star formation can be the origin of the observed proper motions of pulsars. We derive a general expression for the momentum asymmetry in terms of the neutrino energy flux gradient, and show that a nonvanishing effect is induced at the lowest order by a deformed neutrinosphere. In particular, this result is valid for a neutrino flux transported through a spherical atmosphere with constant luminosity.

We establish a method to trace the Lagrangian evolution of extended objects consisting of a multicomponent scalar field in terms of a numerical calculation of field equations in three dimensional Eulerian meshes. We apply our method to the cosmological evolution of global strings and evaluate the energy density, peculiar velocity, Lorentz factor, formation rate of loops, and emission rate of Nambu-Goldstone (NG) bosons. We confirm the scaling behavior with a number of long strings per horizon volume smaller than the case of local strings by a factor of $\sim$ 10. The strategy and the method established here are applicable to a variety of fields in physics.

A light-cone QCD-inspired model, with the mass squared operator consisting of a harmonic oscillator potential as confinement and a Dirac delta interaction, is used to study S-wave meson spectra. The two parameters of the harmonic potential and quark masses are fixed by the masses of $\rho \mathrm{}\left(770\right),$ $\rho \mathrm{}\left(1450\right),$ $J/\psi ,$ $\psi \mathrm{}\left(2S\right),$ $K^{*}\mathrm{}\left(892\right),$ and $B^{*}.$ We apply a renormalization method to define the model, in which the pseudoscalar ground state mass fixes the renormalized strength of the Dirac delta interaction. The model presents a universal and satisfactory description of both singlet and triplet states of S-wave mesons and the corresponding radial excitations.

We study the potential of high-energy linear $e^{+}{e}^{-}$ colliders for the production of gluino pairs within the minimal supersymmetric standard model (MSSM). In this model, the process $e^{+}{e}^{-}\to \tilde{g}\tilde{g}$ is mediated by quark/squark loops, dominantly of the third generation, where the mixing of left- and right-handed states can become large. Taking into account realistic beam polarization effects, photon and $Z^0$ boson exchange, and current mass exclusion limits, we scan the MSSM parameter space for various $e^{+}{e}^{-}$ center-of-mass energies to determine the regions where gluino production should be visible.

We present a new parametrization of the minimal seesaw model, expressing the heavy-singlet neutrino Dirac Yukawa couplings ${(Y}_{\nu }{)}_{\mathrm{ij}}$ and Majorana masses $M_{N_i}$ in terms of effective light-neutrino observables and an auxiliary Hermitian matrix H. In the minimal supersymmetric version of the seesaw model, the latter can be related directly to other low-energy observables, including processes that violate charged lepton flavor and $\mathrm{CP}.\mathrm{}$ This parametrization enables one to respect the stringent constraints on muon-number violation while studying the possible ranges for other observables by scanning over the allowed parameter space of the model. Conversely, if any of the lepton-flavor-violating process is observed, this measurement can be used directly to constrain ${(Y}_{\nu }{)}_{\mathrm{ij}}$ and $M_{N_i}.$ As applications, we study flavor-violating $\tau$ decays and the electric dipole moments of leptons in the minimal supersymmetric seesaw model.

We reanalyze the constraints imposed on lepton-number violating interactions by radiative contributions to neutrino masses at the one- and two-loop levels in supersymmetric models without R parity. The interactions considered are the $\Delta L=1\mathrm{}$ superpotential operators ${\lambda }_{\mathrm{ijk}}{L}_i{L}_j{E}_k^c$ and ${\lambda }_{\mathrm{ijk}}^{\prime }{L}_i{Q}_j{D}_k^c,$ and the $\Delta L=1\mathrm{}$ soft terms $A_{\mathrm{ijk}}{L}_i{L}_j{E}_k^c$ and $A_{\mathrm{ijk}}^{\prime }{L}_i{Q}_j{D}_k^c.$ The two-loop contributions analyzed are those induced by the radiatively generated mass splitting between the $\mathrm{CP}$-even and $\mathrm{CP}$-odd sneutrino states. It is shown how the constraints on the couplings ${\lambda }_{\mathrm{ijk}}$ and ${\lambda }_{\mathrm{ijk}}^{\prime }$ coming from the one-loop analysis can be evaded. In such a case, the two-loop contributions to neutrino masses become important. The combined one- and two-loop analysis yields constraints on the couplings ${\lambda }_{i33\mathrm{}}$ and ${\lambda }_{i33\mathrm{}}^{\prime }$ that are rather difficult to escape. The two-loop analysis yields also constraints on $A_{i33\mathrm{}}$ and $A_{i33\mathrm{}}^{\prime },$ which are not bounded at the one-loop level. More freedom remains for the couplings ${\lambda }_{\mathrm{ijk}},$ ${\lambda }_{\mathrm{ijk}}^{\prime },$ and $A_{\mathrm{ijk}},$ $A_{\mathrm{ijk}}^{\prime },$ when j and k are first- or second-generation indices.

We analyze electroweak baryogenesis in supersymmetric theories with flavor-dependent $\mathrm{CP}$-violating phases. We generalize the standard approach to include the flavor dependence of the $\mathrm{CP}$-violating sources and obtain an analytical approximate expression for the baryon asymmetry of the universe induced by these sources. It is shown that in the framework where the $\mu$ term is real and the chargino sources vanish, large flavor mixing might lead to a substantial baryon asymmetry through the squark contributions, once the condition to have a strong first-order phase transition induced by light right-handed up squarks is relaxed. We derive model independent bounds on the relevant up-squark left-right mass insertions. We show that in supersymmetric models with nonminimal flavor structure these bounds can be reached and the required baryon asymmetry can be generated, while satisfying the constraints coming from the electric dipole moments.

We study the production and decays of top squarks at the Fermilab Tevatron collider in models of low-energy supersymmetry breaking. We consider the case where the lightest standard model (SM) superpartner is a light neutralino that predominantly decays into a photon and a light gravitino. Considering the lighter top squark to be the next-to-lightest standard model superpartner, we analyze top squark signatures associated with jets, photons and missing energy, which lead to signals naturally larger than the associated SM backgrounds. We consider both 2-body and 3-body decays of the top squarks and show that the reach of the Tevatron can be significantly larger than that expected within either the standard supergravity models or models of low-energy supersymmetry breaking in which the top squark is the lightest SM superpartner. For a modest projection of the final Tevatron luminosity, $\mathcal{L}\simeq 4{\mathrm{fb}}^{-1},$ top squark masses of order 300 GeV are accessible at the Tevatron collider in both 2-body and 3-body decay modes. We also consider the production and decay of ten degenerate squarks that are the supersymmetric partners of the five light quarks. In this case we find that common squark masses up to 360 GeV are easily accessible at the Tevatron collider, and that the reach increases further if the gluino is light.

We study the possibility of improving staggered fermions using various fat links in order to reduce perturbative corrections to the gauge-invariant staggered fermion operators. We prove five theorems on SU(3) projection, triviality in renormalization, multiple SU(3) projections, uniqueness, and equivalence. As a result of these theorems, we show that, at the one-loop level, the renormalization of staggered fermion operators is identical between SU(3) projected Fat7 links and hypercubic links, as long as the action and operators are constructed by imposing the same perturbative improvement condition. In addition, we propose a new view of SU(3) projection as a tool of tadpole improvement for the staggered fermion doublers. As a conclusion, we present alternative choices of constructing fat links to improve the staggered fermion action and operators, which deserve further investigation.

A different lattice fermion method is introduced. Staggered domain wall fermions are defined in $2n+1$ dimensions and describe $2^n$ flavors of light lattice fermions with exact $\mathrm{U}\mathrm{}\left(1\right)\mathrm{}\times \mathrm{U}\mathrm{}\left(1\right)\mathrm{}$ chiral symmetry in $2n$ dimensions. As the size of the extra dimension becomes large, $2^n$ chiral flavors with the same chiral charge are expected to be localized on each boundary and the full $\mathrm{SU}{(2\mathrm{}}^n)\times \mathrm{SU}{(2\mathrm{}}^n)$ flavor chiral symmetry is expected to be recovered. SDWF give a different perspective into the inherent flavor mixing of lattice fermions and by design present an advantage for numerical simulations of lattice QCD thermodynamics. The chiral and topological index properties of the SDWF Dirac operator are investigated. And, there is a surprise ending.

Production of electroweak bosons in $e^{+}{e}^{-}$ annihilation into quarks and into leptons at energies much greater than 100 GeV is considered. We account for double-logarithmic contributions to all orders in electroweak couplings. It is assumed that the bosons are emitted in multi-Regge kinematics. Explicit expressions for the scattering amplitudes of the process are obtained. It is shown that the cross sections of the photon and Z production have the identical energy dependence and asymptotically their ratio depends only on the Weinberg angle, whereas the energy dependence of the cross section of W production is suppressed by a factor of $s^{-0.4}$ compared to them.

We discuss the relation between the observed charged current, elastic scattering, and neutral current fluxes and the flavor fractional content of the solar neutrino flux seen by SNO. By using existing estimates of the cross sections for the charged and neutral current reactions which take into account the detector resolution, we show how the forthcoming SNO rates unconstrained by the standard ${}^8\mathrm{B}$ shape could test the oscillations into active states. We perform a model independent analysis for the Super-Kamiokande and SNO data, assuming a nondistorted spectrum.

We examine the constraints on the nonradiative decay of neutrinos from the observations of solar neutrino experiments. The standard oscillation hypothesis among three neutrinos solves the solar and atmospheric neutrino problems. The decay of a massive neutrino mixed with the electron neutrino results in the depletion of the solar neutrino flux. We introduce neutrino decay in the oscillation hypothesis and demand that decay does not spoil the successful explanation of solar and atmospheric observations. We obtain a lower bound on the ratio of the lifetime over the mass of ${\nu }_2,$ ${\tau }_2{/m}_2>22.7\mathrm{}\mathrm{s}/\mathrm{MeV}$ for the Mikheyev-Smirnov-Wolfenstein solution of the solar neutrino problem and ${\tau }_2{/m}_2>27.8\mathrm{}\mathrm{s}/\mathrm{MeV}$ for the vacuum oscillation solution (at $99\%$ C.L.).

We have performed a search for radiative b-hadron decays using events produced in $p\overline{p}$ collisions at $\sqrt{s}=1.8\mathrm{}\mathrm{TeV}$ and collected by the Collider Detector at Fermilab. The decays we considered were $B_d^0\to K^{*0}(\to K^{-}{\pi }^{+})\gamma ,$ $B_s^0\to \phi (\to K^{+}{K}^{-})\gamma ,$ ${\Lambda }_b^0\to \Lambda (\to p{\pi }^{-})\gamma ,$ and their charge conjugates. Two independent methods to identify photons from such decays were employed. In the first method, the photon was detected in the electromagnetic calorimeter. In the second method, the photon was identified by an electron-positron pair produced through the external photon conversion before the tracking detector volume. By combining the two methods we obtain upper limits on the branching fractions for the $B_d^0,$ $B_s^0,$ and ${\Lambda }_b^0$ radiative decays which, at the 95% confidence level, are found to be $\mathcal{B}(B_d^0\to K^{*0}\gamma )<\mathrm{}1.4\mathrm{}\times {10}^{-4},$ $\mathcal{B}(B_s^0\to \phi \gamma )<\mathrm{}1.6\mathrm{}\times {10}^{-4},$ and $\mathcal{B}({\Lambda }_b^0\to \Lambda \gamma )<\mathrm{}1.9\mathrm{}\times {10}^{-3}.$

The renormalization evolution of all parameters in the neutrino mass matrix depends only on one variable, the energy scale. This fact, coupled with rephasing considerations, leads to a set of renormalization invariants, correlating the evolution of physical parameters. We obtain these invariants explicitly and discuss their implications.

A four-parameter Majorana neutrino mass matrix is proposed, which is exactly diagonalizable with two mixing angles, one of which is $\pi /4\mathrm{}$ and the other large but less than $\pi /4.\mathrm{}$ The form of this mass matrix allows seven realizations of the present data on atmospheric and solar neutrino oscillations: three have the normal hierarchy, two have the inverse hierarchy, and two have three nearly degenerate masses. The possible inclusion of $\mathrm{CP}$ violation is also discussed.