We derive the general upper bounds on the mass of the lightest neutralino, as a function of the gluino mass, in different supersymmetry breaking models with minimal particle content and the standard model gauge group. This includes models with gravity mediated supersymmetry breaking, as well as models with anomaly mediated supersymmetry breaking. We include the next-to-leading order corrections in our evaluation of these bounds. We then expand the mass matrix in powers of $M_Z/\mu$ and find the upper bound on the mass of the lightest neutralino from this expansion. By scanning over all of the parameter space, we find that the bound we have obtained can be saturated. We compare the general upper bound on the lightest neutralino mass to the upper bound that is obtained when the radiative electroweak symmetry breaking scenario is assumed.

Models of supersymmetric grand unified theories based on the $\mathrm{SU}{\mathrm{}\left(5\right)\mathrm{}}_{\mathrm{GUT}}\times \mathrm{U}{\mathrm{}\left(N\right)\mathrm{}}_H$ gauge group $\mathrm{}(N=2,3\mathrm{})\mathrm{}$ have a symmetry that guarantees light Higgs doublets and the absence of dimension-5 proton-decay operators. We analyze the proton decay induced by the gauge-boson exchange in these models. Upper bounds on the proton lifetime are obtained: $\tau \left(\overrightarrow{p}{\pi }^0{e}^{+}\right)\lesssim 6.0\times {10}^{33}\mathrm{yr}$ in the $\mathrm{SU}{\mathrm{}\left(5\right)\mathrm{}}_{\mathrm{GUT}}\times \mathrm{U}{\mathrm{}\left(2\right)\mathrm{}}_H$ model and $\tau \left(\overrightarrow{p}{\pi }^0{e}^{+}\right)\lesssim 5.3\times {10}^{35}\mathrm{yr}$ in the $\mathrm{SU}{\mathrm{}\left(5\right)\mathrm{}}_{\mathrm{GUT}}\times \mathrm{U}{\mathrm{}\left(3\right)\mathrm{}}_H$ model. Various uncertainties in the predictions are also discussed.

For nonrelativistic QCD the velocity renormalization group correlates the renormalization scales for ultrasoft, potential and soft degrees of freedom. Here we discuss the renormalization of operators by ultrasoft gluons. We show that renormalization of soft vertices can induce new operators, and also present a procedure for correctly subtracting divergences in mixed potential-ultrasoft graphs. Our results affect the running of the spin-independent potentials in QCD. The change for the NNLL $t\overline{t}$ cross section near threshold is very small, being at the $\lesssim 1\%$ level and essentially independent of the energy. We also discuss implications for analyzing situations where ${\mathrm{mv}}^2\sim {\Lambda }_{\mathrm{QCD}}.$

We calculate the radiative corrections to the unpolarized and the four polarized spectrum and rate functions in the leptonic decay of a polarized $\mu$ into a polarized electron. The new feature of our calculation is that we keep the mass of the final state electron finite which is mandatory if one wants to investigate the threshold region of the decay. Analytical results are given for the energy spectrum and the polar angle distribution of the final state electron whose longitudinal and transverse polarization is calculated. We also provide analytical results on the integrated spectrum functions. We analyze the $m_e\to 0$ limit of our general results and investigate the quality of the $m_e\to 0$ approximation. In the $m_e\to 0$ case we discuss in some detail the role of the $O\left(\alpha \right)$ anomalous helicity flip contribution of the final electron which survives the $m_e\to 0$ limit. The results presented in this paper also apply to the leptonic decays of polarized $\tau$ leptons for which we provide numerical results.

We study the transition form factors between pseudoscalar and vector mesons using a covariant fermion field theory model in $3+1$ dimensions. Performing the light-front calculation in the $q^{+}=0\mathrm{}$ frame in parallel with the manifestly covariant calculation, we note that the suspected nonvanishing zero-mode contribution to the light-front current $J^{+}$ does not exist in our analysis of transition form factors. We also perform the light-front calculation in a purely longitudinal $q^{+}>0\mathrm{}$ frame and confirm that the form factors obtained directly from the timelike region are identical to the ones obtained by the analytic continuation from the spacelike region. Our results for the $\overrightarrow{B}{D}^{*}l{\nu }_l$ decay process satisfy the constraints on the heavy-to-heavy semileptonic decays imposed by the flavor independence in the heavy quark limit.

We show that the correction to the Paschos-Wolfenstein relation associated with charge symmetry violation in the valence quark distributions is essentially model independent. It is proportional to a ratio of quark momenta that is independent of $Q^2.$ This result provides a natural explanation of the surprisingly good agreement found between our earlier estimates within several different models. When applied to the recent NuTeV measurement, this effect significantly reduces the discrepancy with other determinations of the Weinberg angle.

Just as the single fluxbrane is quantum mechanically unstable to the nucleation of a locally charged spherical brane, so intersecting fluxbranes are unstable to various decay modes. Each individual element of the intersection can decay via the nucleation of a spherical brane, but uncharged spheres can also be nucleated in the region of intersection. For special values of the fluxes, however, intersecting fluxbranes are supersymmetric, and so are expected to be stable. We explicitly consider the instanton describing the decay modes of the two-element intersection (an F5-brane in the string theory context), and show that in dimensions greater than four the action for the decay mode of the supersymmetric intersection diverges. This observation allows us to show that stable intersecting fluxbranes should also exist in type 0A string theory.

Here we address the problem of bosonizing massive fermions without making expansions in the fermion masses in both massive ${\mathrm{QED}}_2$ and ${\mathrm{QED}}_3$ with N fermion flavors including also a Thirring coupling. We start from two-point correlators involving the $U\left(1\right)\mathrm{}$ fermionic current and the gauge field. From the tensor structure of those correlators we prove that the $U\left(1\right)\mathrm{}$ current must be identically conserved (topological) in the corresponding bosonized theory in both $D=2\mathrm{}$ and $D=3\mathrm{}$ dimensions. We find an effective generating functional in terms of bosonic fields which reproduces these two-point correlators and from that we obtain a map of the Lagrangian density ${\overline{\psi }}^r$$\left(i\partial /-m\right){\psi }^r$ into a bosonic one in both dimensions. This map is nonlocal but it is independent of the electromagnetic and Thirring couplings, at least in the quadratic approximation for the fermionic determinant.

Using the eternal BTZ black hole as a concrete example, we show how spacelike singularities and horizons can be described in terms of AdS/CFT amplitudes. Our approach is based on analytically continuing amplitudes defined in a Euclidean signature. This procedure yields finite Lorentzian amplitudes. The naive divergences associated with the Milne type singularity of BTZ black holes are regulated by an $i\epsilon$ prescription inherent in the analytic continuation and a cancellation between future and past singularities. The boundary description corresponds to a tensor product of two CFTs in an entangled state, as in previous work. We give two bulk descriptions corresponding to two different analytic continuations. In the first, only regions outside the horizon appear explicitly, and so amplitudes are manifestly finite. In the second, regions behind the horizon and on both sides of the singularity appear, thus yielding finite amplitudes for virtual particles propagating through the black hole singularity. This equivalence between descriptions only outside and both inside and outside the horizon is reminiscent of the ideas of black hole complementarity.

We discuss the holographic principle in a radiation-dominated, closed Friedmann-Robertson-Walker universe with a positive cosmological constant. By introducing a cosmological D bound on the entropy of matter in the universe, we can write the Friedmann equation governing the evolution of the universe in the form of the Cardy formula. When the cosmological D bound is saturated, the Friedmann equation coincides with the Cardy-Verlinde formula describing the entropy of radiation in the universe. As a concrete model, we consider a brane universe in the background of Schwarzschild–de Sitter black holes. It is found that the cosmological D bound is saturated when the brane crosses the black hole horizon of the background. At that moment, the Friedmann equation coincides with the Cardy-Verlinde formula describing the entropy of radiation matter on the brane.

We propose that the observed baryon asymmetry of the Universe can naturally arise from a net asymmetry generated in the right-handed sneutrino sector at fairly low reheat temperatures. The initial asymmetry in the sneutrino sector is produced from the decay of the inflaton, and is subsequently transferred into the standard model (s)lepton doublet via three-body decay of the sneutrino. Our scenario relies on two main assumptions: a considerable branching ratio for the inflaton decay to the right-handed (s)neutrinos, and Majorana masses which are generated by the Higgs mechanism. The marked feature of this scenario is that the lepton asymmetry is decoupled from the neutrino Dirac Yukawa couplings. We exhibit that our scenario can be embedded within minimal models which seek the origin of a tiny mass for neutrinos.

In this work, we present the gravitational field generated by a cosmic string carrying a timelike current in the scalar-tensor gravities. The mechanism of formation and evolution of wakes is fully investigated in this framework. We show explicitly that the inclusion of electromagnetic properties for the string induces logarithmic divergences in the accretion problem.

Simple curvaton models can generate a mixture of correlated primordial adiabatic and isocurvature perturbations. The baryon and cold dark matter isocurvature modes differ only by an observationally null mode in which the two perturbations almost exactly compensate, and therefore have proportional effects at linear order. We discuss the cosmic microwave background (CMB) anisotropy in general mixed models, and give a simple approximate analytic result for the large scale CMB anisotropy. Working numerically we use the latest Wilkinson Microwave Anisotropy Probe (WMAP) observations and a variety of other data to constrain the curvaton model. We find that models with an isocurvature contribution are not favored relative to simple purely adiabatic models. However a significant primordial totally correlated baryon isocurvature perturbation is not ruled out. Certain classes of curvaton model are thereby ruled out; other classes predict enough non-Gaussianity to be detectable by the Planck satellite. In the Appendixes we review the relevant equations in the covariant formulation and give series solutions for the radiation dominated era.

In the quintessential inflationary model, the same master field that drives inflation becomes, later on, the dynamical source of the (present) accelerated expansion. Quintessential inflationary models require a curvature scale at the end of inflation around ${10}^{-6}{M}_{\mathrm{P}}$ in order to explain the large scale fluctuations observed in the microwave sky. If the curvature scale at the end of inflation is much smaller than ${10}^{-6}{M}_{\mathrm{P}},$ the large scale adiabatic mode may be produced thanks to the relaxation of a scalar degree of freedom, which will be generically denoted, according to the recent terminology, as the curvaton field. The production of the adiabatic mode is analyzed in detail in the case of the minimal quintessential inflationary model originally proposed by Peebles and Vilenkin.

We investigate first order phase transitions from β-equilibrated hadronic matter to color-flavor-locked quark matter in a compact star interior. The hadronic phase including hyperons and a Bose-Einstein condensate of $K^{-}$ mesons is described by a relativistic field theoretical model with density dependent meson-baryon couplings. The early appearance of hyperons and/or a Bose-Einstein condensate of $K^{-}$ mesons delays the onset of the phase transition to higher density. In the presence of hyperons and/or a $K^{-}$ condensate, the overall equations of state become softer, resulting in smaller maximum masses than the cases without hyperons and a $K^{-}$ condensate. We find that the maximum mass neutron stars may contain a mixed phase core of hyperons, $K^{-}$ condensate, and color superconducting quark matter. Depending on the parameter space, we also observe that there is a stable branch of superdense stars called the third family branch beyond the neutron star branch. Compact stars in the third family branch may contain a pure color superconducting core and have radii smaller than those of the neutron star branch. Our results are compared with the recent observations on RX J185635-3754 and the recently measured mass-radius relationship by the X-ray Multi Mirror–Newton observatory.

We analyze and discuss the quantum noise in signal-recycled laser interferometer gravitational-wave detectors, such as Advanced LIGO, using a heterodyne readout scheme and taking into account the optomechanical dynamics. Contrary to homodyne detection, a heterodyne readout scheme can simultaneously measure more than one quadrature of the output field, providing an additional way of optimizing the interferometer sensitivity, but at the price of additional noise. Our analysis provides the framework needed to evaluate whether a homodyne or heterodyne readout scheme is more optimal for second generation interferometers from an astrophysical point of view. As a more theoretical outcome of our analysis, we show that as a consequence of the Heisenberg uncertainty principle the heterodyne scheme cannot convert conventional interferometers into (broadband) quantum non-demolition interferometers.

According to quantum measurement theory, “speed meters”—devices that measure the momentum, or speed, of free test masses—are immune to the standard quantum limit (SQL). It is shown that a Sagnac-interferometer gravitational-wave detector is a speed meter and therefore in principle it can beat the SQL by large amounts over a wide band of frequencies. It is shown, further, that, when one ignores optical losses, a signal-recycled Sagnac interferometer with Fabry-Perot arm cavities has precisely the same performance, for the same circulating light power, as the Michelson speed-meter interferometer recently invented and studied by Purdue and the author. The influence of optical losses is not studied, but it is plausible that they be fairly unimportant for the Sagnac interferometer, as for other speed meters. With squeezed vacuum (squeeze factor $e^{-2R}=0.1)$ injected into its dark port, the recycled Sagnac interferometer can beat the SQL by a factor $\sqrt{10}\simeq 3$ over the frequency band $10\mathrm{Hz}\lesssim f\lesssim 150\mathrm{Hz}$ using the same circulating power $I_c\sim 820$ kW as is to be used by the (quantum limited) second-generation Advanced LIGO interferometers—if other noise sources are made sufficiently small. It is concluded that the Sagnac optical configuration, with signal recycling and squeezed-vacuum injection, is an attractive candidate for third-generation interferometric gravitational-wave detectors (LIGO-III and EURO).

We perform a complete analysis of $\Delta S=2\mathrm{}$ processes in the kaon system and evaluate $\Delta M_K$ and ${\epsilon }_K$ in the left-right supersymmetric model. We include analytic expressions for the contributions of gluinos, neutralinos, and charginos. We obtain general constraints on off-diagonal mass terms between the first two generations of both down-type and up-type squarks. In the down-squark sector, we compare the results with gluino-only estimates. In the up-squark sector, we find a complete set of bounds on all combinations of chirality conserving or chirality flipping parameters. Finally, we comment on the size of the bounds obtained by imposing left-right symmetry in the squark sector.

The Z boson can decay to a pair of light gluinos through loop-mediated processes. Based on unitarity of the S matrix, the imaginary part of the decay amplitude is computed in the presence of a light bottom squark. This imaginary part can provide useful information on the full amplitude. Implications are discussed for a recently proposed light gluino and light bottom squark scenario.

In this paper we take the first step towards a complete next-to-next-to-leading logarithmic (NNLL) calculation of the inclusive decay rate for $\overrightarrow{B}{X}_s\gamma .$ We consider the virtual corrections of the order of ${\alpha }_s^2{n}_f$ to the matrix elements of the operators $O_1,$ $O_2$ and $O_8$ and evaluate the real and virtual contributions to $O_7.$ These corrections are expected to be numerically important. We observe a strong cancellation between the contributions from the current-current operators and $O_7$ and obtain, after applying naive non-Abelianization, a reduction of the branching ratio of 3.9% (for $\mu =3.0\mathrm{}\mathrm{GeV})$ and an increase of 3.4% (for $\mu =9.6\mathrm{}\mathrm{GeV}).\mathrm{}$