Supernova experiments to characterize dark energy require a well designed low redshift program; we consider this for both ongoing/near term (e.g. Supernova Legacy Survey) and comprehensive future (e.g. SNAP) experiments. The derived criteria are: a supernova sample centered near $z\approx 0.05$ comprising 150–500 (in the former case) and 300–900 (in the latter case) well measured supernovae. Low redshift Type Ia supernovae play two important roles for cosmological use of the supernova distance-redshift relation: as an anchor for the Hubble diagram and as an indicator of possible systematics. An innate degeneracy in cosmological distances implies that 300 nearby supernovae nearly saturate their cosmological leverage for the first use, and their optimum central redshift is $z\approx 0.05$. This conclusion is strengthened upon including velocity flow and magnitude offset systematics. Limiting cosmological parameter bias due to supernova population drift (evolution) systematics plausibly increases the requirement for the second use to less than about 900 supernovae.

Perturbative dynamics of gravity is investigated for high-energy scattering and in black hole backgrounds. In the latter case, a straightforward perturbative analysis fails, in a close parallel to the failure of the former when the impact parameter reaches the Schwarzschild radius. This suggests a flaw in a semiclassical description of physics on spatial slices that intersect both outgoing Hawking radiation and matter that has carried information into a black hole; such slices are instrumental in a general argument for black hole information loss. This indicates a possible role for the proposal that nonperturbative gravitational physics is intrinsically nonlocal.

The approximate renormalized one-loop effective action of the quantized massive scalar, spinor and vector field in a large mass limit, i.e., the lowest order of the DeWitt-Schwinger expansion involves the coincidence limit of the Hadamard-DeWitt coefficient $a_3$. Building on this and using Wald’s approach we shall construct the general expression describing entropy of the spherically-symmetric static black hole being the solution of the semiclassical field equations. For the concrete case of the quantum-corrected Reissner-Nordström black hole this result coincides, as expected, with the entropy obtained by integration of the first law of black hole thermodynamics with a suitable choice of the integration constant. The case of the extremal quantum-corrected black hole is briefly considered.

A framework is developed in which one can write down the constraint equations on a three-dimensional hypersurface of arbitrary signature. It is then applied to isolated and dynamical horizons. The derived equations can be used to extract physically relevant quantities describing the horizon irrespective to whether it is isolated (null) or dynamical at a given instant of time. Furthermore, a small perturbation of isolated horizons are considered, and finally a family of an axially symmetric exact solution of the constraint equations on a dynamical horizon is presented.

We discuss some possible implications of a two-dimensional toy model for black hole evaporation in noncommutative field theory. While the noncommutativity we consider does not affect gravity, it can play an important role in the dynamics of massless and Hermitian scalar fields in the event horizon of a Schwarzschild black hole. We find that noncommutativity will affect the flux of outgoing particles and the nature of its UV/IR divergences. Moreover, we show that the noncommutative interaction does not affect Leahy’s and Unruh’s interpretation of thermal ingoing and outgoing fluxes in the black hole evaporation process. Thus, the noncommutative interaction still destroys the thermal nature of fluxes. In the process, some nonlocal implications of the noncommutativity are discussed.

Within the inflationary scenario, Planck scale physics should have affected the comoving modes’ initial conditions and early evolution, thereby potentially affecting the inflationary predictions for the cosmic microwave background (CMB). This issue has been studied extensively on the basis of various models for how quantum field theory (QFT) is modified and finally breaks down towards the Planck scale. In one model, in particular, an ultraviolet cutoff was implemented into QFT through generalized uncertainty relations which have been motivated from general quantum gravity arguments and from string theory. Here, we improve upon prior numerical and semianalytical results by presenting the exact mode solutions for both de Sitter and power-law inflation in this model. This provides an explicit map from the modes’ initial conditions, which are presumably set by quantum gravity, to the modes’ amplitudes at horizon crossing and thus to the inflationary predictions for the CMB. The solutions’ particular behavior close to the cutoff scale suggests unexpected possibilities for how the degrees of freedom of QFT emerge from the Planck scale.

The convergence of the iterative solutions of the transport equations of cosmic muon and tau neutrinos propagating through Earth is studied and analyzed. For achieving a fast convergence of the iterative solutions of the coupled transport equations of ${\nu }_{\tau }$, ${\overline{\nu }}_{\tau }$ and the associated ${\tau }^{\pm }$ fluxes, a new semianalytic input algorithm is presented where the peculiar $\tau$-decay contributions are implemented already in the initial zeroth order input. Furthermore, the common single transport equation for muon neutrinos is generalized by taking into account the contributions of secondary ${\nu }_{\mu }$ and ${\overline{\nu }}_{\mu }$ fluxes due to the prompt $\tau$-decay $\tau \to {\nu }_{\mu }$ initiated by the associated tau flux. Differential and total nadir-angle-integrated upward-going ${\mu }^{-}+{\mu }^{+}$ event rates are presented for underground neutrino telescopes and compared with the muon rates initiated by the primary ${\nu }_{\mu }$, ${\nu }_{\tau }$, and $\tau$ fluxes.

We present data for the axial coupling constant $g_A$ of the nucleon obtained in lattice QCD with two degenerate flavors of dynamical nonperturbatively improved Wilson quarks. The renormalization is also performed nonperturbatively. For the analysis we give a chiral extrapolation formula for $g_A$ based on the small scale expansion scheme of chiral effective field theory for two degenerate quark flavors. Applying this formalism in a finite volume, we derive a formula that allows us to extrapolate our data simultaneously to the infinite volume and to the chiral limit. Using the additional lattice data in finite volume, we are able to determine the axial coupling of the nucleon in the chiral limit without imposing the known value at the physical point.

We discuss a constraint of conformal symmetry in the analysis of the pion form factor. The usual power-law behavior of the form factor obtained in the perturbative QCD analysis can also be attained by taking negligible quark masses in the nonperturbative quark model analysis, confirming the recent AdS/CFT correspondence. We analyze the transition from soft to hard contributions in the pion form factor considering a momentum-dependent dynamical quark mass from an appreciable constituent quark mass at low momentum region to a negligible current quark mass at high momentum region. We find a correlation between the shape of nonperturbative quark distribution amplitude and the amount of soft and hard contributions to the pion form factor.

We consider the process of associated stop-chargino production in the MSSM at LHC and show that, at the simplest Born level, the production rate is dramatically sensitive to the choice of the benchmark points, oscillating from potentially visible maxima of the picobarn size to much smaller, hardly visible, values. Adopting a canonical choice of SM-type CKM matrices, we also show that in some visible cases the total rate exhibits a possibly relevant dependence on $\tan \beta$.

We present an improved measurement of the ${\eta }^{\prime }$ meson energy spectrum in ${\rm Y}(1S)$ decays, using $1.2{\mathrm{fb}}^{-1}$ of data taken at the ${\rm Y}(1S)$ center-of-mass energy with the CLEO III detector. We compare our results with models of the ${\eta }^{\prime }$ gluonic form factor that have been suggested to explain the unexpectedly large $B\to {\eta }^{\prime }{X}_s$ rate. Models based on perturbative QCD fail to fit the data for large ${\eta }^{\prime }$ energies, and thus an explanation outside the realm of the Standard Model or an improved understanding of nonperturbative QCD effects may be needed to account for this large rate.

We present a measurement of the top quark mass with the matrix element method in the $\mathrm{\text{lepton}}+\mathrm{\text{jets}}$ final state. As the energy scale for calorimeter jets represents the dominant source of systematic uncertainty, the matrix element likelihood is extended by an additional parameter, which is defined as a global multiplicative factor applied to the standard energy scale. The top quark mass is obtained from a fit that yields the combined statistical and systematic jet energy scale uncertainty. Using a data set of $0.4{\mathrm{fb}}^{-1}$ taken with the D0 experiment at Run II of the Fermilab Tevatron Collider, the mass of the top quark is measured using topological information to be: $m_{\mathrm{top}}^{\ell +\mathrm{jets}}(\mathrm{topo})={169.2}_{-7.4}^{+5.0}(\mathrm{stat}+JES{)}_{-1.4}^{+1.5}(\mathrm{syst})\mathrm{GeV}$, and when information about identified $b$ jets is included: $m_{\mathrm{top}}^{\ell +\mathrm{jets}}(b\mathrm{\text{-tag}})={170.3}_{-4.5}^{+4.1}(\mathrm{stat}+JES{)}_{-1.8}^{+1.2}(\mathrm{syst})\mathrm{GeV}$. The measurements yield a jet energy scale consistent with the reference scale.

It has been argued that the bosonic sectors of supersymmetric $SU(N)$ Yang-Mills theory, and of QCD with a single fermion in the antisymmetric (or symmetric) tensor representation, are equivalent in the $N\to \infty$ limit. If true, this correspondence can provide useful insight into properties of real QCD (with fundamental representation fermions), such as predictions [with $O(1/N)$ corrections] for the nonperturbative vacuum energy, the chiral condensate, and a variety of other observables. Several papers asserting to have proven this large $N$ “orientifold equivalence” have appeared. By considering theories compactified on ${\mathbb{R}}^3\times S^1$, we show explicitly that this large $N$ equivalence fails for sufficiently small radius, where our analysis is reliable, due to spontaneous symmetry breaking of charge-conjugation symmetry in QCD with an antisymmetric (or symmetric) tensor representation fermion. This theory is also chirally symmetric for small radius, unlike super-Yang-Mills theory. The situation is completely analogous to large-$N$ equivalences based on orbifold projections: simple symmetry realization conditions are both necessary and sufficient for the validity of the large $N$ equivalence. Whether these symmetry realization conditions are satisfied depends on the specific nonperturbative dynamics of the theory under consideration. Unbroken charge-conjugation symmetry is necessary for validity of the large $N$ orientifold equivalence. Whether or not this condition is satisfied on ${\mathbb{R}}^4$ (or ${\mathbb{R}}^3\times S^1$ for sufficiently large radius) is not currently known.

The nonuniform black-strings branch, which emerges from the critical Gregory-Laflamme string, is numerically constructed in dimensions $6\le D\le 11$ and extended into the strongly nonlinear regime. All the solutions are more massive and less entropic than the marginal string. We find the asymptotic values of the mass, the entropy and other physical variables in the limit of large horizon deformations. By explicit metric comparison we verify that the local geometry around the waist of our most nonuniform solutions is conelike with less than 10% deviation. We find evidence that in this regime the characteristic length scale has a power-law dependence on a parameter along the branch of the solutions, and estimate the critical exponent.

Motivated by the lessons of black hole complementarity, we develop a causal patch description of eternal inflation. We argue that an observer cannot ascribe a semiclassical geometry to regions outside his horizon, because the large-scale metric is governed by the fluctuations of quantum fields. In order to identify what is within the horizon, it is necessary to understand the late time asymptotics. Any given worldline will eventually exit from eternal inflation into a terminal vacuum. If the cosmological constant is negative, the universe crunches. If it is zero, then we find that the observer’s fate depends on the mechanism of eternal inflation. Worldlines emerging from an eternal inflation phase driven by thermal fluctuations end in a singularity. By contrast, if eternal inflation ends by bubble nucleation, the observer can emerge into an asymptotic, locally flat region. As evidence that bubble collisions preserve this property, we present an exact solution describing the collision of two bubbles.

We reconsider constraints on Brans-Dicke theories arising from the requirement of successful big bang nucleosynthesis. Such constraints typically arise by imposing that the universe be radiation-dominated at early times, and therefore restricting the contribution that a Brans-Dicke scalar could make to the energy budget of the universe. However, in this paper we show how the dynamics of the Brans-Dicke scalar itself can mimic a radiation-dominated kinematics, thereby allowing successful nucleosynthesis with a sizable contribution to the total cosmic energy density. In other words Newton’s constant may dynamically acquire values quite different from that today, even though the evolution mimics radiation domination. This possibility significantly relaxes the existing bounds on Brans-Dicke fields, and opens the door to new possibilities for early universe cosmology. The necessary fine tunings required by such an arrangement are identified and discussed.

We investigate whether postulating the existence of Lorentz-violating, $CPT$-conserving interactions allows three-neutrino solutions to the LSND anomaly that are also consistent with all other neutrino data. We show that Lorentz-violating interactions that couple only to one of the active neutrinos have the right properties to explain all the data. The details of the data make this solution unattractive. We find, for example, that a highly nontrivial energy dependence of the Lorentz-violating interactions is required.

We measure the dependence of ${\overline{B}}^0\to D^{*+}{e}^{-}{\overline{\nu }}_e$ on the decay angles and momentum transfer. The data sample consists of $\sim 86\times {10}^6$ $B\overline{B}$-pairs accumulated on the $\mathit{{\rm Y}}(4\mathrm{S})$ resonance by the BABAR detector at the asymmetric $e^{+}{e}^{-}$ collider PEP-II. We specify the three form factors by two ratios $R_1$ and $R_2$, and by a single parameter ${\rho }^2$ characterizing the polynomial representing $h_{A_1}$, the function which describes the momentum-transfer dependence of the form factor $A_1$. We determine $R_1$, $R_2$, and ${\rho }^2$ using an unbinned maximum likelihood fit to the full decay distribution. The results are $R_1=1.396\pm 0.060\pm 0.035\pm 0.027$, $R_2=0.885\pm 0.040\pm 0.022\pm 0.013$, and ${\rho }^2=1.145\pm 0.059\pm 0.030\pm 0.035$. The stated uncertainties are the statistical from the data, statistical from the size of the Monte Carlo sample and the systematic uncertainty, respectively. In addition, based on this measurement, we give an updated value for the CKM matrix element $|V_{cb}|$.

We propose a method of construction of a cubic interaction in massless higher spin gauge theory both in flat and in AdS space-times of arbitrary dimensions. We consider a triplet formulation of the higher spin gauge theory and generalize the higher spin symmetry algebra of the free model to the corresponding algebra for the case of cubic interaction. The generators of this new algebra carry indexes which label the three higher spin fields involved into the cubic interaction. The method is based on the use of oscillator formalism and on the Becchi-Rouet-Stora-Tyutin (BRST) technique. We derive general conditions on the form of cubic interaction vertex and discuss the ambiguities of the vertex which result from field redefinitions. This method can in principle be applied for constructing the higher spin interaction vertex at any order. Our results are a first step towards the construction of a Lagrangian for interacting higher spin gauge fields that can be holographically studied.