One of the most disturbing difficulties in thinking about the cosmological constant is that it is not stable under radiative corrections. The feedback mechanism proposed by Mukohyama and Randall is a dynamical way to protect a zero or small cosmological constant against radiative corrections. Hence, while this by itself does not solve the cosmological constant problem, it can help in solving the problem. In the present paper we investigate stability and gravity in this approach and show that the feedback mechanism is both classically and quantum mechanically stable and has self-consistent, stable dynamics.

We explore the possibility that the masses for the first two generations of fermions and the quark flavor violation are generated radiatively in the Minimal Supersymmetric Standard Model. We assume that the source of all flavor violation resides in the the supersymmetry-breaking sector and is transmitted radiatively to the Standard Model fermion sector through finite corrections at low-energy. The approximate radiative alignment between the Yukawa and soft supersymmetry-breaking matrices, helps to suppress some of the supersymmetric contributions to flavor changing processes, overcoming current experimental constraints. This mechanism may also explain the nonobservation of proton decay, since flavor conservation in the superpotential would imply the suppression of dimension-five operators in supersymmetric grand unified theories.

We construct an effective low energy Lagrangian using constraints imposed by the renormalization group. Degrees of freedom are gluons and a scalar glueball. This effective theory has a dual description as classical gluodynamics on a curved conformal background. Color fields are dynamically confined, and the strong coupling freezes at distances larger than the glueball size. We make specific predictions (in particular, on the $N_c$ dependence of glueball properties) which can be tested in lattice simulations of gluodynamics.

We present an approximate gap equation for different crystalline structures of the Larkin-Ovchinnikov-Fulde-Ferrel phase of high density QCD at $T=0$. This equation is derived by using an effective condensate term obtained by averaging the inhomogeneous condensate over distances of the order of the crystal lattice size. The approximation is expected to work better far off any second-order phase transition. As a function of the difference of the chemical potentials of the up and down quarks, $\delta \mu$, we get that the octahedron is energetically favored from $\delta \mu ={\Delta }_0/\sqrt{2}$ to $0.95{\Delta }_0$, where ${\Delta }_0$ is the gap for the homogeneous phase, while in the range $0.95{\Delta }_0–1.32{\Delta }_0$ the face-centered cube prevails. At $\delta \mu =1.32{\Delta }_0$ a first-order phase transition to the normal phase occurs.

A model for baryonic Regge trajectories compatible with the threshold behavior required by unitarity and asymptotic behavior in agreement with analyticity constraints is given in explicit form. Widths and masses of the baryonic resonances on the $N$ and $\Delta$ trajectories are reproduced. The MacDowell symmetry is exploited and an application is given.

We find the condition that the primordial baryon asymmetry is not washed out in the $\mathrm{S}\mathrm{U}(2{)}_L$ triplet Higgs model by solving the Boltzmann equation. We further require that the model is compatible with the recent results of the neutrino oscillation experiments and the Wilkinson Microwave Anisotropy Probe, and the constraints on the $\rho$ parameter imposed by the CERN LEP. We finally obtain the allowed region of the parameters in the model.

We search for lepton flavor violating couplings via doubly charged bilepton (or doubly charged Higgs) exchange in electron-positron annihilation process ${\mathrm{e}}^{+}{\mathrm{e}}^{-}\to {\mu }^{+}{\mu }^{-},{\tau }^{+}{\tau }^{-}$ using CERN LEP data at the center of mass energies between 189–207 GeV. Standard model program ZFITTER has been used to calculate radiative corrections. We find that $g_L^2/M_L^2<O({10}^{-6})\mathrm{G}\mathrm{e}{\mathrm{V}}^{\mathrm{-}\mathrm{2}}$ at 95% C.L. for flavor violating scalar and vector bilepton couplings.

Using the well-known “displace, cut and reflect” method used to generate disks from given solutions of Einstein field equations, we construct static charged disks made of perfect fluid based on the Reissner-Nordström solution in isotropic coordinates. We also derive a simple stability condition for charged and noncharged perfect fluid disks. As expected, we find that the presence of charge increases the regions of instability of the disks.

We introduce $N$-parameter perturbation theory as a new tool for the study of nonlinear relativistic phenomena. The main ingredient in this formulation is the use of the Baker-Campbell-Hausdorff formula. The associated machinery allows us to prove the main results concerning the consistency of the scheme to any perturbative order. Gauge transformations and conditions for gauge invariance at any required order can then be derived from a generating exponential formula via a simple Taylor expansion. We outline the relation between our novel formulation and previous developments.

Part of the CMB polarization signal in the direction of galaxy clusters is produced by Thomson scattering of the CMB temperature quadrupole. In principle this allows measurement of the CMB power spectrum harmonic $C_2(z)$ with higher accuracy (at $z>0$) than the cosmic variance limit imposed by sample variance on one CMB sky. However the observed signals are statistically correlated if the comoving separation between the clusters is small enough. Thus one cannot reduce the sample variance by more than roughly the number of separate regions available which produce uncorrelated signals, as first pointed out by Kamionkowski and Loeb. In this paper we analyze in detail the procedure outlined by Kamionkowski and Loeb, computing the correlation of the polarization signals by considering the variation of the spherical harmonic expansion coefficients of the temperature anisotropy on our past light cone. Given a hypothetical set of Stokes parameter measurements of the CMB polarization in the directions of galaxy clusters, distributed at random on a given redshift shell, we show how to construct an estimator of the angular power spectrum harmonic $C_2$ at that redshift. We then compare the variance of this estimator with the cosmic variance of the CMB multipole on our sky which probes the same scale. We find that in fact the cosmic variance is not reducible below the single sky CMB value using the cluster method. Thus this method is not likely to be of use for reconstruction of the primordial power spectrum. However the method does yield a measurement of $C_2$ as a function of redshift with increasing accuracy at higher redshift, and thus potentially a probe of the mechanism which may have suppressed the quadrupole. We also examine to what extent the redshift dependence of $C_2$ can be used to probe the time changing potential anisotropy as the universe evolves into the vacuum dominated phase (the late-time integrated Sachs-Wolfe effect). We find that this effect is not observable in the time dependence of $C_2$ since it is swamped by cosmic variance, but there is an observable signature in the correlation functions of the Stokes parameters.

We discuss the prospects for detection of high energy neutrinos from dark matter (DM) annihilation at the galactic center (GC). Despite the large uncertainties associated with our poor knowledge of the distribution of dark matter in the innermost regions of the Galaxy, we determine an upper limit on the neutrino flux by requiring that the associated gamma-ray emission does not exceed the observed flux. We conclude that a neutrino flux from the GC will not be observable by Antares if dark matter is made of neutralinos with mass smaller than 650 GeV, while for heavier neutralinos, corresponding to models that will soon be probed by HESS (high energy stereoscopic system), the upper limit on the neutrino flux is barely above the Antares sensitivity. The detection of a larger flux would either require an alternative explanation, in terms of astrophysical processes, or the adoption of other dark matter candidates, disfavouring the case for neutralinos.

This article derives an optimal (i.e., unbiased, minimum variance) estimator for the pseudodetector strain for a pair of colocated gravitational wave interferometers (such as the pair of LIGO interferometers at its Hanford Observatory), allowing for possible instrumental correlations between the two detectors. The technique is robust and does not involve any assumptions or approximations regarding the relative strength of gravitational wave signals in the Hanford pair with respect to other sources of correlated instrumental or environmental noise. An expression is given for the effective power spectral density of the combined noise in the pseudodetector. This can then be introduced into the standard optimal Wiener filter used to cross-correlate detector data streams in order to obtain an optimal estimate of the stochastic gravitational wave background. In addition, a dual to the optimal estimate of strain is derived. This dual is constructed to contain no gravitational wave signature and can thus be used as an “off-source” measurement to test algorithms used in the “on-source” observation.

In supersymmetry, the flavor mixing between top-squark (stop) and charm-squark (scharm) induces the flavor-changing neutral-current (FCNC) stop decay ${\tilde{t}}_1\to c{\tilde{\chi }}_1^0$. Searching for this decay serves as a probe of soft supersymmetry breaking parameters. Focusing on the stop pair production followed by the FCNC decay of one stop and the charge-current decay of the other stop, we investigate the potential of detecting this FCNC stop decay at the Fermilab Tevatron, the CERN Large Hadron Collider and the next-generation $e^{+}{e}^{-}$ linear collider. We find that this decay may not be accessible at the Tevatron, but could be observable at the Large Hadron Collider and the linear collider with high sensitivity for some part of parameter space.

We explore the transitions $B(0^{+})$ to $B\pi$ and $B_s(0^{+})$ to $BK$ from lattice QCD with $N_f=2$ flavors of sea quark, using the static approximation for the heavy quark. We evaluate the effective coupling constants, predicting a $B(0^{+})$ to $B\pi$ width of around 160 MeV. Our result for the coupling strength adds to the evidence that the $B_s(0^{+})$ meson is not predominantly a molecular state ($BK$).

The nature of Mashhoon’s spin-rotation coupling is the interaction between a particle spin (gravitomagnetic moment) and a gravitomagnetic field. Here we will consider the coupling of graviton spin to the weak gravitomagnetic fields by analyzing the Lagrangian density of weak gravitational field, and hence study the purely gravitational generalization of Mashhoon’s spin-rotation couplings.

A single massless fermionic field with an Abelian $U(1)$ gauge interaction (electrodynamics of a massless Dirac fermion) is studied by a variational method. Even without the insertion of any extra interaction the vacuum is shown to be unstable towards a particle-antiparticle condensate. The single particle excitations do acquire a mass and behave as massive Fermi particles. An explicit low-energy gap equation has been derived and numerically solved. Some consequences of condensation and mass generation are discussed in the framework of the standard model.

The periodic standing-wave method for binary inspiral computes the exact numerical solution for periodic binary motion with standing gravitational waves, and uses it as an approximation to slow binary inspiral with outgoing waves. Important features of this method presented here are: (i) the mathematical nature of the “mixed” partial differential equations to be solved, (ii) the meaning of standing waves in the method, (iii) computational difficulties, and (iv) the “effective linearity” that ultimately justifies the approximation. The method is applied to three-dimensional nonlinear scalar model problems, and the numerical results are used to demonstrate extraction of the outgoing solution from the standing-wave solution, and the role of effective linearity.

The inflationary production of magnetic field seeds for galaxies is discussed. The analysis is carried out by writing the wave equation of the electromagnetic field in curved space-times. The conformal invariance is broken by taking into account the interaction of the electromagnetic field with the curvature tensor of the form $\lambda R_{\alpha \beta \gamma \delta }{F}^{\alpha \beta }{F}^{\gamma \delta }$. Such a term induces an amplification of the magnetic field during the reheating phase of the universe, but no growth of the magnetic field occurs in the de Sitter epoch. The resulting primordial magnetic field turns out to have strengths of astrophysical interest.

We suggest a new cosmological scenario which naturally guarantees the smallness of scalar masses and vacuum expectation values , without invoking supersymmetry or any other (nongravitationally coupled) new physics at low energies. In our framework, the scalar masses undergo discrete jumps due to nucleation of closed branes during (eternal) inflation. The crucial point is that the step size of variation decreases in the direction of decreasing scalar mass. This scenario yields exponentially large domains with a distribution of scalar masses, which is sharply peaked around a hierarchically small value of the mass. This value is the “attractor point” of the cosmological evolution.

We discuss the dynamics of the accretion flow onto a black hole driven by Poynting flux in a simplified model of a two-dimensional accretion disk. In this simplified model, the condition of the stationary accretion flow is found to impose a nontrivial constraint on the magnetic field configuration. The effect of the magnetic field on the accretion flow is discussed in detail using the paraboloidal- and hyperboloidal-type configurations for the poloidal structure suggested by Blandford in 1976. It is demonstrated explicitly that the angular velocity of the disk ${\Omega }_D$ deviates from the Keplerian angular velocity. The angular velocity of the rigidly rotating magnetic surface ${\Omega }_F$ does not have to be the same as the angular velocity of the disk for the paraboloidal-type configuration. But for the hyperboloidal type configuration, it is found that we can set ${\Omega }_F={\Omega }_D$, which corresponds to an accretion disk of perfect conductor. We discuss the numerical solutions of the stream equation for stationary accretion flow in the Schwarzschild background using a paraboloidal-type configuration. The dynamics of the accretion disk is found to depend strongly on the ratio of the accretion rate to the magnetic field strength.