Solar neutrino observations coupled with the recent KamLAND data suggest that spin-flavor precession scenario does not play a major role in neutrino propagation in the solar matter. We provide approximate analytical formulas and numerical results to estimate the contribution of the spin-flavor precession, if any, to the electron neutrino survival probability when the magnetic moment and magnetic field combination is small.

We present a measurement of the $t\overline{t}$ production cross section using $194{\mathrm{pb}}^{-1}$ of CDF II data using events with a high transverse momentum electron or muon, three or more jets, and missing transverse energy. The measurement assumes 100% $t\to Wb$ branching fraction. Events consistent with $t\overline{t}$ decay are found by identifying jets containing heavy-flavor semileptonic decays to muons. The dominant backgrounds are evaluated directly from the data. Based on 20 candidate events and an expected background of $9.5\pm 1.1$ events, we measure a production cross section of $5.3\pm {3.3}_{-1.0}^{+1.3}\mathrm{pb}$, in agreement with the standard model.

We develop a semiclassical approximation scheme for the constraint equations of supersymmetric canonical quantum gravity. This is achieved by a Born-Oppenheimer type of expansion, in analogy to the case of the usual Wheeler-DeWitt equation. The formalism is only consistent if the states at each order depend on the gravitino field. We recover at consecutive orders the Hamilton-Jacobi equation, the functional Schrödinger equation, and quantum gravitational correction terms to this Schrödinger equation. In particular, the following consequences are found: (i) the Hamilton-Jacobi equation and therefore the background spacetime must involve the gravitino, (ii) a (many-fingered) local time parameter has to be present on super Riem $\Sigma$ (the space of all possible tetrad and gravitino fields), (iii) quantum supersymmetric gravitational corrections affect the evolution of the very early Universe. The physical meaning of these equations and results, in particular, the similarities to and differences from the pure bosonic case, are discussed.

We explore the dynamics of assisted quintessence, where more than one scalar field is present with the same potential. For potentials with tracking solutions, the fields naturally approach the same values—in the context of inflation this leads to the assisted inflation phenomenon where several fields can cooperate to drive a period of inflation though none is able to individually. For exponential potentials, we study the fixed points and their stability confirming results already in the literature, and then carry out a numerical analysis to show how assisted quintessence is realized. For inverse power-law potentials, we find by contrast that there is no assisted behavior—indeed those are the unique (monotonic) potentials where several fields together behave just as a single field in the same potential. More generally, we provide an algorithm for generating a single-field potential giving equivalent dynamics to multifield assisted quintessence.

We investigate the possibility that dark matter and the baryon asymmetry of the Universe are generated by the same mechanism, following an idea initially proposed by Kuzmin and recently discussed by Kitano and Low. In our model, based on a left-right extension of the standard model, the baryon asymmetry is generated through leptogenesis and dark matter is made of relic stable right-handed neutrinos with mass $\sim \mathrm{\text{few}}\mathrm{GeV}$. Constraints on the model imply that this form of dark matter would unfortunately escape detection.

We investigate the cosmology of a recently proposed deformation of Einstein gravity, emerging from quantum gravity heuristics. The theory is constructed to have de Sitter space as a vacuum solution, and thus to be relevant to the accelerating universe. However, this solution turns out to be unstable, and the true phase space of cosmological solutions is significantly more complex, displaying two late-time power-law attractors—one accelerating and the other dramatically decelerating. It is also shown that nonaccelerating cosmologies sit on a separatrix between the two basins of attraction of these attractors. Hence it is impossible to pass from a decelerating cosmology to an accelerating one, as required in standard cosmology for consistency with nucleosynthesis and structure formation and compatibility with the data inferred from supernovae Ia. We point out that alternative models of the early universe, such as the one investigated here might provide possible ways to circumvent these requirements.

The recently observed color-suppressed ${\overline{B}}^0\to D^0{\pi }^0$, $D^0{\eta }^{(\prime )}$, $D_s^{+}{K}^{-}$ and $D^0{\overline{K}}^0$ decay modes all have rates larger than expected, hinting at the presence of final state interactions. We study rescattering effects in $\overline{B}\to DP$, $D\overline{K}$ and $\overline{D}\overline{K}$ modes in the quasielastic approach, which is extended to accommodate $D^0{\eta }^{\prime }$ without using U(3) symmetry. The ${\overline{D}}^0\overline{K}$ modes are of interest in the determination of the unitarity angle ${\varphi }_3/\gamma$. The updated $DP$ data are used to extract the effective Wilson coefficients $a_1^{\mathrm{eff}}\simeq 0.92$, $a_2^{\mathrm{eff}}\simeq 0.22$, three strong phases $\delta \simeq 62°$, $\theta \simeq 24°$, $\sigma \simeq 127°$, and the mixing angle $\tau \simeq 2°$. The values of $\delta$ and $\theta$ are close to our previous results. The smallness of $\tau$ implies small mixing of $D^0{\eta }_1$ with other modes. Predictions for $D^0{K}^{-}$, $D^{+}{K}^{-}$ and $D^0{\overline{K}}^0$ agree with data. Since strong interaction respects charge conjugation symmetry, the framework applies to $\overline{B}\to \overline{D}\overline{K}$, and rates for ${\overline{D}}^0{K}^{-}$, $D^{-}{K}^0$, $D_s^{-}{\pi }^0$, $D_s^{-}\eta$ and $D_s^{-}{\eta }^{\prime }$ modes are predicted. From $B^{-}\to {\overline{D}}^0{K}^{-}$ and $D^0{K}^{-}$ rates, we find $r_B=0.09\pm 0.02$, where the error is propagated from the experimental $DP$ rate uncertainties. The error on $r_B$ is doubled when the universality on $a_2^{\mathrm{eff}}$ is relaxed.

Using explicit solutions of the QCD transport equations, we derive an effective potential for an anisotropic quark-gluon plasma which under plausible assumptions holds beyond the Hard Loop approximation. The configurations, which are unstable in the linear response approach, are characterized by a negative quadratic term of the effective potential. The signs of higher-order terms can be either negative or positive, depending on the parton momentum distribution. In the case of a Gaussian momentum distribution, the potential is negative and unbound from below. Therefore, the modes, which are unstable for gauge fields of small amplitude, remain unstable for arbitrary large amplitudes. We also present an example of a momentum distribution which gives a negative quadratic term of the effective potential but the whole potential has a minimum and it grows for sufficiently large gauge fields. Then, the system is weakly unstable. The character of the instability is important for the dynamical evolution of the plasma system.

We show that a double seesaw framework for neutrino masses with $\mu -\tau$ exchange symmetry can lead to one of the right-handed seesaw partners of the light neutrinos being massless. This can play the role of a light sterile neutrino, giving a $3+1$ model that explains the Liquid Scintillator Neutrino Detector (LSND) results. We get a very economical scheme, which makes it possible to predict the full $4\times 4$ neutrino mass matrix if $CP$ is conserved. Once $CP$ violation is included, the effect of the LSND mass range sterile neutrino is to eliminate the lower bound on neutrinoless double beta decay rate which exists for the three neutrino case with inverted mass hierarchy. The same strategy can also be used to generate a natural $3+2$ model for LSND, which is also equally predictive for the $CP$ conserving case in the limit of exact $\mu -\tau$ symmetry.

We study the polarization of antihyperon in lepton induced reactions such as $e^{+}{e}^{-}\to \overline{H}+X$ and $l+p\to l^{\prime }+\overline{H}+X$ with polarized beams using different models for spin transfer in high energy fragmentation processes. We compare the results with the available data and those for hyperons. We make predictions for future experiments.

We consider $\mathrm{d}{\mathrm{S}}_2/\mathrm{CF}{\mathrm{T}}_1$ where the asymptotic symmetry group of the de Sitter spacetime contains the Virasoro algebra. We construct representations of the Virasoro algebra realized in the Fock space of a massive scalar field in de Sitter space, built as excitations of the Euclidean vacuum state. These representations are unitary, without highest weight, and have vanishing central charge. They provide a prototype for a new class of conformal field theories dual to de Sitter backgrounds in string theory. The mapping of operators in the CFT to bulk quantities is described in detail. We comment on the extension to $\mathrm{d}{\mathrm{S}}_3/\mathrm{CF}{\mathrm{T}}_2$.

We consider non(anti)commutative superspace with coordinate-dependent deformation parameters $C^{\alpha \beta }$. We show that a chiral $\mathcal{N}=1/2$ supersymmetry can be defined and that chiral and antichiral superfields are still closed under the Moyal-Weyl associative product implementing the deformation. A consistent $\mathcal{N}=1/2$ super Yang-Mills deformed theory can be constructed provided $C^{\alpha \beta }$ satisfies a suitable condition which can be connected with the graviphoton background at the origin of the deformation. After adding matter, we also discuss the Konishi anomaly and the gluino condensation.

We show that the BFT embedding method is problematic for mixed systems (systems possessing both first and second class constraints). The Chern-Simons theory as an example is worked out in detail. We give two methods to solve the problem leading to two different types of finite order BFT embedding for Chern-Simons theory.

When the neutral current neutrino-neutrino interaction is treated completely, rather than as an interaction among angle-averaged distributions, or as a set of flavor-diagonal effective potentials, the result can be flavor mixing at a speed orders of magnitude faster than that one would anticipate from the measured neutrino oscillation parameters. It is possible that the energy spectra of the three active species of neutrinos emerging from a supernova are nearly identical.

We introduce a new formulation of baryon chiral perturbation theory which improves the ultraviolet behavior of propagators and can be interpreted as a smooth cutoff regularization scheme. It is equivalent to the standard approach, preserves all symmetries, and therefore satisfies the Ward identities. Our formulation is equally well defined in the vacuum, one-nucleon, and few-nucleon sectors of the theory. The equations (Bethe-Salpeter, Lippmann-Schwinger, etc.) for the scattering amplitudes of the few-nucleon sector are free of divergences in the new approach. Unlike the usual cutoff regularization, our “cutoffs” are parameters of the Lagrangian and do not have to be removed.

It is shown that a nonrotating macroscopic black hole with very large horizon area can remain in stable thermal equilibrium with Hawking radiation provided its mass, as a function of horizon area, exceeds its microcanonical entropy, i.e., its entropy when isolated, without thermal radiation or accretion, and having a constant horizon area (in appropriate units). The analysis does not use properties of specific classical spacetimes, but depends only on the plausible assumption that the mass is a function of the horizon area for large areas.

We study the fully nonlinear dynamical evolution of binary black hole data, whose orbital parameters are specified via the effective potential method for determining quasicircular orbits. The cases studied range from the Cook-Baumgarte innermost stable circular orbit (ISCO) to significantly beyond that separation. In all cases we find the black holes to coalesce (as determined by the appearance of a common apparent horizon) in less than half an orbital period. The results of the numerical simulations indicate that the initial holes are not actually in quasicircular orbits, but that they are in fact nearly plunging together. The dynamics of the final horizon are studied to determine physical parameters of the final black hole, such as its spin, mass, and oscillation frequency, revealing information about the inspiral process. We show that considerable resolution is required to extract accurate physical information from the final black hole formed in the merger process, and that the quasinormal modes of the final hole are strongly excited in the merger process. For the ISCO case, by comparing physical measurements of the final black hole formed to the initial data, we estimate that less than 3% of the total energy is radiated in the merger process.

We calculate the systematic errors in the weak gravitational lensing power spectrum which would be caused by spatially varying calibration (i.e. multiplicative) errors, such as might arise from uncorrected seeing or extinction variations. The systematic error is fully described by the angular two-point correlation function of the systematic in the case of the 2D lensing that we consider here. We investigate three specific cases: Gaussian, “patchy,” and exponential correlation functions. In order to keep systematic errors below statistical errors in future LSST-like surveys, the spatial variation of calibration should not exceed $3\%$ rms. This conclusion is independently true for all forms of correlation function we consider. The relative size of the E- and B-mode power spectrum errors does, however, depend upon the form of the correlation function, indicating that one cannot repair the E-mode power spectrum systematics by means of the B-mode measurements.

We present a nonthermal leptogenesis scenario following standard supersymmetric hybrid inflation, in the case where light neutrinos acquire mass via the usual seesaw mechanism and inflaton decay to heavy right-handed neutrino superfields is kinematically disallowed, or the right-handed neutrinos which can be decay products of the inflaton are unable to generate sufficient baryon asymmetry via their subsequent decay. The primordial lepton asymmetry is generated through the decay of the inflaton into light particles by the interference of one-loop diagrams with exchange of different right-handed neutrinos. The mechanism requires superpotential couplings explicitly violating a U(1) R-symmetry and R-parity. We take into account the constraints from neutrino masses and mixing and the preservation of the primordial asymmetry. We consider two models, one without and one with $\mathrm{SU}(2{)}_R$ gauge symmetry. We show that the former is viable, whereas the latter is ruled out. Although the broken R-parity need not have currently observable low-energy signatures, some R-parity-violating slepton decays may be detectable in the future colliders.