We describe a search for $Z$ boson pair production in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ with the D0 detector at the Fermilab Tevatron Collider using a data sample corresponding to an integrated luminosity of $2.7{\mathrm{fb}}^{-1}$. Using the final state decay $ZZ\to {\ell }^{+}{\ell }^{-}\nu \overline{\nu }$ (where $\ell =e$ or $\mu$) we find a signal with a 2.6 standard deviations significance (2.0 expected) corresponding to a cross section of $\sigma (p\overline{p}\to ZZ+X)=2.01\pm 0.93(\mathrm{stat})\pm 0.29(\mathrm{sys})\mathrm{pb}$.

Photoproduction of beauty quarks in events with two jets and an electron associated with one of the jets has been studied with the ZEUS detector at HERA using an integrated luminosity of $120{\mathrm{pb}}^{-1}$. The fractions of events containing $b$ quarks, and also of events containing $c$ quarks, were extracted from a likelihood fit using variables sensitive to electron identification as well as to semileptonic decays. Total and differential cross sections for beauty and charm production were measured and compared with next-to-leading-order QCD calculations and Monte Carlo models.

It was recently proposed by the second author to consider lattice formulations of QCD in which complete actions, including the gauge part, are built explicitly from a given Dirac operator $D$. In a simple example of such theory, the gauge action is proportional to the trace of Ginsparg–Wilson operator $D$ chosen to define the quark dynamics. This construction relies on the proposition that the classical limit of lattice gauge operator $\mathrm{tr}D(x,x)$ is proportional to $\mathrm{tr}{F}^2(x)$ (up to an additive constant). Here we show this for the case of the overlap Dirac operator using both analytical and numerical methods. We carry out the same analysis also for the tensor component of $D$, which is similarly related to the field-strength tensor $F$, and obtain results identical to our previous derivation that used a different approach. The corresponding proportionality constants are computed to high precision for a wide range of the negative mass parameter values, and it is verified that they are the same in finite and infinite volumes.

We introduce braneworlds with nonconstant tension, strengthening the analogy with fluid membranes, which exhibit a temperature dependence according to the empirical law established by Eötvös. This new degree of freedom allows for evolving gravitational and cosmological constants, the latter being a natural candidate for dark energy. We establish the covariant dynamics on a brane with variable tension in full generality, by considering asymmetrically embedded branes and allowing for nonstandard model fields in 5-dimensional space-time. Then we apply the formalism for a perfect fluid on a Friedmann brane, which is embedded in a 5-dimensional charged Vaidya-anti-de Sitter space-time.

In this paper, we study the physical properties and characteristics of matter forming thin accretion disks in static and spherically symmetric wormhole spacetimes. In particular, the time averaged energy flux, the disk temperature, and the emission spectra of the accretion disks are obtained for these exotic geometries and are compared with the Schwarzschild solution. It is shown that more energy is emitted from the disk in a wormhole geometry than in the case of the Schwarzschild potential and the conversion efficiency of the accreted mass into radiation is more than a factor of 2 higher for the wormholes than for static black holes. These effects in the disk radiation are confirmed in the radial profiles of temperature corresponding to theses flux distributions, and in the emission spectrum $\omega L(\omega )$ of the accretion disks. We conclude that specific signatures appear in the electromagnetic spectrum, thus leading to the possibility of distinguishing wormhole geometries by using astrophysical observations of the emission spectra from accretion disks.

If gravity respects quantum mechanics, it is important to identify the essential postulates of a quantum framework capable of incorporating gravitational phenomena. Such a construct likely requires elimination or modification of some of the “standard” postulates of quantum mechanics, in particular, those involving time and measurement. This paper proposes a framework that appears sufficiently general to incorporate some expected features of quantum gravity. These include the statement that space and time may only emerge approximately and relationally. One perspective on such a framework is as a sort of generalization of the S-matrix approach to dynamics. Within this framework, more dynamical structure is required to fully specify a theory; this structure is expected to lack some of the elements of local quantum field theory. Some aspects of this structure are discussed, both in the context of scattering of perturbations about a flat background, and in the context of cosmology.

We survey observational constraints on the parameter space of inflation and axions and map out two allowed windows: the classic window and the inflationary anthropic window. The cosmology of the latter is particularly interesting; inflationary axion cosmology predicts the existence of isocurvature fluctuations in the cosmic microwave background, with an amplitude that grows with both the energy scale of inflation and the fraction of dark matter in axions. Statistical arguments favor a substantial value for the latter, and so current bounds on isocurvature fluctuations imply tight constraints on inflation. For example, an axion Peccei-Quinn scale of ${10}^{16}\mathrm{GeV}$ excludes any inflation model with energy scale $>3.8\times {10}^{14}\mathrm{GeV}$ ($r>2\times {10}^{-9}$) at 95% confidence, and so implies negligible gravitational waves from inflation, but suggests appreciable isocurvature fluctuations.

The evolution of dark matter in central areas of galaxies is considered (the Milky Way is taken as an example). It is driven by the scattering off of dark matter particles by bulge stars, their absorption by the supermassive black hole, and self-annihilation. This process is described by the diffusion equation in the phase space of energy and angular momentum. The equation was integrated for several different models of initial dark matter distribution and using various assumptions about the dynamical factors. It turns out that because the Milky Way center is rather dynamically old ($\sim 4$ relaxation times $t_r$), the difference in initial conditions almost vanishes. The density attains a nearly universal profile, and the $\gamma$-ray flux from dark matter annihilation lies in a rather narrow range, which enables a more robust determination of the dark matter parameters. By presenting the mass of dark matter inside the black hole, the sphere of influence ($r<2\mathrm{pc}$) has been reduced approximately twice, mostly because of heating by stars. It is shown that the dynamics of dark matter for $t\gtrsim t_r$ is determined mainly by stars outside the sphere of influence.

We develop a new method for reconstructing cluster-mass profiles and large-scale structure from the cosmic microwave background (CMB). By analyzing the likelihood of CMB lensing, we analytically prove that standard quadratic estimators for CMB lensing are unbiased and achieve the optimal condition only in the limit of no lensing; they become progressively biased and suboptimal, when the lensing effect is large, especially for clusters that can be found by ongoing Sunyaev-Zel’dovich surveys. Adopting an alternative approach to the CMB likelihood, we construct a new maximum likelihood estimator that utilizes delensed CMB temperature fields based on an assumed model. We analytically show that this estimator asymptotically approaches the optimal condition as our assumed model is refined, and we numerically show that as we iteratively apply it to CMB maps our estimator quickly converges to the true model with a factor of 10 less number of clusters than standard quadratic estimators need. For realistic CMB experiments, we demonstrate the applicability of the maximum likelihood estimator with tests against numerical simulations in the presence of CMB secondary contaminants. With significant improvement on the signal-to-noise ratio, our new maximum likelihood estimator can be used to measure the cluster-mass cross-correlation functions at different redshifts, probing the evolution of dark energy.

We implement the Wang-Landau algorithm in the context of $SU(N)$ lattice gauge theories. We study the quenched, reduced version of the lattice theory and calculate its density of states for $N=20$, 30, 40, 50. We introduce a variant of the original algorithm in which the weight function used in the update does not asymptote to a fixed function, but rather continues to have small fluctuations that enhance tunneling. We formulate a method to evaluate the errors in the density of states, and use the result to calculate the dependence of the average action density and the specific heat on the ‘t Hooft coupling $\lambda$. This allows us to locate the coupling ${\lambda }_t$ at which a strongly first-order transition occurs in the system. For $N=20$ and 30 we compare our results with those obtained using Ferrenberg-Swendsen multihistogram reweighting and find agreement with errors of 0.2% or less. Extrapolating our results to $N=\infty$, we find $({\lambda }_t{)}^{-1}=0.3148(2)$. We remark on the significance of this result for the validity of quenched large-$N$ reduction of $SU(N)$ lattice gauge theories.

Numerical simulations with access to all possible meson quantum numbers $J^{PC}$ are presented using two-flavor (up and down) quenched twisted mass lattice QCD with three different lattice spacings and four different quark masses. The connection between the quantum numbers ($P$ and $C$) and the symmetries of the twisted mass action is discussed, as is the connection between $J$ and the lattice rotation group, for the 400 operators used in this study. Curve fitting of this large data set is accomplished by using an evolutionary fitting algorithm. Results are reported for conventional and exotic quantum numbers.

For some time, the Draco dwarf spheroidal galaxy has garnered interest as a possible source for the indirect detection of dark matter. Its large mass-to-light ratio and relative proximity to the Earth provide favorable conditions for the production of a detectable flux of gamma rays from dark matter self-annihilation in its core. The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is an atmospheric Cherenkov telescope located in Albuquerque, NM capable of detecting gamma rays at energies above 100 GeV. We present the results of the STACEE observations of Draco during the 2005–2006 observing season totaling 10.2 hours of live time after cuts. We do not detect a significant gamma-ray signal from Draco, and place an upper limit on a power-law spectrum of $\frac{dN}{dE}{|}_{\mathrm{Draco}}<1.6\times {10}^{-13}(\frac{E}{220\mathrm{GeV}}{)}^{-2.2}\gamma {\mathrm{s}}^{-1}{\mathrm{cm}}^{-2}{\mathrm{GeV}}^{-1}$ Assuming a smooth Navarro-Frenk-White profile for the dark-matter halo and an annihilation spectrum, we also derive upper limits for the cross-section-velocity product ($⟨\sigma v⟩$) for weakly interacting massive particles self-annihilation.

The topological susceptibility is calculated within the Hamiltonian approach to Yang-Mills theory in Coulomb gauge, using the vacuum wave functional previously determined by a variational solution of the Yang-Mills Schrödinger equation. The numerical result agrees qualitatively with the predictions of lattice simulations.

The walls of bubbles in a first-order phase transition can propagate either as detonations, with a velocity larger than the speed of sound, or deflagrations, which are subsonic. We calculate the gravitational radiation that is produced by turbulence during a phase transition which develops via deflagration bubbles. We take into account the fact that a deflagration wall is preceded by a shock front which distributes the latent heat throughout space and influences other bubbles. We show that turbulence can induce peak values of ${\Omega }_{\mathrm{GW}}$ as high as $\sim {10}^{-9}$. We discuss the possibility of detecting at LISA (Laser Interferometer Space Antennae) gravitational waves produced in the electroweak phase transition with wall velocities $v_w\lesssim {10}^{-1}$, which favor electroweak baryogenesis.

We investigate the Born-Infeld–anti–de Sitter (BIAdS) black hole solutions in the four dimensions, which is a nonlinear generalization of the Reissner-Norström-AdS (RNAdS) black hole. We analyze all thermodynamic quantities of the BIAdS black hole in the canonical ensembles, which are characterized by the charge $Q$, the mass $M$, the nonlinear parameter $b$, comparing with those of the RNAdS and Schwarzschild-AdS black hole. We find the forbidden region of $0\le bQ<0.5$ for the presence of a charged BIAdS black hole. We also discuss the Hawking-Page phase transitions in the BIAdS black holes. Here we obtain a new Hawking-Page phase transition for the $bQ=0.5$ critical BIAdS black hole.

In this paper, we show that dark matter in the form of dense matter/antimatter nuggets could provide a natural and unified explanation for several distinct bands of diffuse radiation from the core of the Galaxy spanning over 13 orders of magnitude in frequency. We fix all of the phenomenological properties of this model by matching to x-ray observations in the keV band, and then calculate the unambiguously predicted thermal emission in the microwave band, at frequencies smaller by 11 orders of magnitude. Remarkably, the intensity and spectrum of the emitted thermal radiation are consistent with—and could entirely explain—the so-called “WMAP haze”: a diffuse microwave excess observed from the core of our Galaxy by the Wilkinson Microwave Anisotropy Probe (WMAP). This provides another strong constraint of our proposal, and a remarkable nontrivial validation. If correct, our proposal identifies the nature of the dark matter, explains baryogenesis, and provides a means to directly probe the matter distribution in our Galaxy by analyzing several different types of diffuse emissions.

The influence of a possible nonzero chemical potential $\mu$ on the nature of dark energy is investigated by assuming that the dark energy is a relativistic perfect simple fluid obeying the equation of state, $p=\omega \rho$ ($\omega <0$, constant). The entropy condition, $S\ge 0$, implies that the possible values of $\omega$ are heavily dependent on the magnitude, as well as on the sign of the chemical potential. For $\mu >0$, the $\omega$ parameter must be greater than $-1$ (vacuum is forbidden) while for $\mu <0$ not only the vacuum but even a phantomlike behavior ($\omega <-1$) is allowed. In any case, the ratio between the chemical potential and temperature remains constant, that is, $\mu /T={\mu }_0/T_0$. Assuming that the dark energy constituents have either a bosonic or fermionic nature, the general form of the spectrum is also proposed. For bosons $\mu$ is always negative and the extended Wien’s law allows only a dark component with $\omega <-1/2$, which includes vacuum and the phantomlike cases. The same happens in the fermionic branch for $\mu <0$. However, fermionic particles with $\mu >0$ are permitted only if $-1<\omega <-1/2$. The thermodynamics and statistical arguments constrain the equation-of-state parameter to be $\omega <-1/2$, a result surprisingly close to the maximal value required to accelerate a Friedmann-Robertson-Walker–type universe dominated by matter and dark energy ($\omega \lesssim -10/21$).

It has been found recently that propagators, e.g. the cross correlation spectra of the cosmic fields with the initial density field, decay exponentially at large $k$ in an Eulerian description of the dynamics. We explore here similar quantities defined for a Lagrangian space description. We find that propagators in Lagrangian space do not exhibit the same properties: they are found not to be monotonic functions of time, and to track back the linear growth rate at late time (but with a renormalized amplitude). These results have been obtained with a novel method which we describe alongside. It allows the formal resummation of the same set of diagrams as those that led to the known results in Eulerian space. We provide a tentative explanation for the marked differences seen between the Eulerian and the Lagrangian cases, and we point out the role played by the vorticity degrees of freedom that are specific to the Lagrangian formalism. This provides us with new insights into the late-time behavior of the propagators.

We study the spectrum of cosmological fluctuations in the D3/D7 brane inflationary universe with particular attention to the parametric excitation of entropy modes during the reheating stage. The same tachyonic instability which renders reheating in this model very rapidly leads to an exponential growth of entropy fluctuations during the preheating stage which in turn may induce a large contribution to the large-scale curvature fluctuations. We take into account the effects of long wavelength quantum fluctuations in the matter fields. As part of this work, we perform an analytical analysis of the reheating process. We find that the initial stage of preheating proceeds by the tachyonic instability channel. An upper bound on the time it takes for the energy initially stored in the inflaton field to convert into fluctuations is obtained by neglecting the local fluctuations produced during the period of tachyonic decay and analyzing the decay of the residual homogeneous field oscillations, which proceeds by parametric resonance. We show that, in spite of the fact that the resonance is of the narrow-band type, it is sufficiently efficient to rapidly convert most of the energy of the background fields into matter fluctuations.