The dynamic process of unstable D-branes decaying into stable ones with one dimension lower can be described by a tachyon field with a Dirac-Born-Infeld effective action. In this paper we investigate the fluctuation modes of the tachyon field around a two-parameter family of static solutions representing an array of brane-antibrane pairs. Besides a pair of zero modes associated with the parameters of the solution, and instabilities associated with annihilation of the brane-antibrane pairs, we find states corresponding to excitations of the tachyon field around the brane and in the bulk. In the limit that the brane thickness tends to zero, the support of the eigenmodes is limited to the brane, consistent with the idea that propagating tachyon modes drop out of the spectrum as the tachyon field approaches its ground state. The zero modes, and other low-lying excited states, show a fourfold degeneracy in this limit, which can be identified with some of the massless superstring modes in the brane-antibrane system. Finally, we also discuss the slow motion of the solution corresponding to the decay process in the moduli space, finding a trajectory which oscillates periodically between the unstable D-brane and the brane-antibrane pairs of one dimension lower.

In studying the dynamics of large $N_c$, $SU(N_c)$ gauge theory at finite temperature with fundamental quark flavors in the quenched approximation, we observe a first order phase transition. A quark condensate forms at finite quark mass, and the value of the condensate varies smoothly with the quark mass for generic regions in parameter space. At a particular value of the quark mass, there is a finite discontinuity in the condensate’s vacuum expectation value, corresponding to a first order phase transition. We study the gauge theory via its string dual formulation using the AdS/CFT conjecture, the string dual being the near-horizon geometry of $N_c$ D3-branes at finite temperature, ${\mathrm{AdS}}_5\mathrm{\text{−}}\mathrm{\text{Schwarzschild}}\times S^5$, probed by a D7-brane. The D7-brane has topology ${\mathbb{R}}^4\times S^3\times S^1$ and allowed solutions correspond to either the $S^3$ or the $S^1$ shrinking away in the interior of the geometry. The phase transition represents a jump between branches of solutions having these two distinct D-brane topologies. The transition also appears in the meson spectrum.

All order Seiberg-Witten maps of gauge parameter, gauge field, and matter fields are given as a closed recursive formula. These maps are obtained by analyzing the order by order solutions of the gauge consistency and equivalence conditions as well as by directly solving Seiberg-Witten differential equations. The explicit third order non-Abelian and fourth order Abelian Seiberg-Witten maps of gauge parameter and gauge field are also presented.

Within the superfield formalism, we study the ultraviolet properties of the three-dimensional supersymmetric quantum electrodynamics. The theory is shown to be finite at all loop orders in a particular gauge.

We investigate the canonical quantization in the framework of $N=1$ simple supergravity for the case of a very simple gravitational midisuperspace described by Gowdy $T^3$ cosmological models. We consider supersymmetric quantum cosmology in the mentioned midisuperspace, where a matrix representation for the gravitino covector-spinor is used. The full Lorentz constraint and its implications for the wave function of the Universe are analyzed in detail. We found that there are indeed physical states in the midisuperspace sector of the theory in contrast to the case of minisuperspace where there exist no physical states.

We examine static perfect fluid spheres in the presence of a cosmological constant. Because of the cosmological constant, new classes of exact matter solutions are found. One class of solutions requires the Nariai metric in the vacuum region. Another class generalizes the Einstein static universe such that neither its energy density nor its pressure is constant throughout the spacetime. Using analytical techniques we derive conditions depending on the equation of state to locate the vanishing pressure surface. This surface can, in general, be located in regions where, going outwards, the area of the spheres associated with the group of spherical symmetry is decreasing. We use numerical methods to integrate the field equations for realistic equations of state and find consistent results.

We study perturbations of a Schwarzschild black hole in Chern-Simons modified gravity. We begin by showing that Birkhoff’s theorem holds for a wide family of Chern-Simons coupling functions, a scalar field present in the theory that controls the strength of the Chern-Simons correction to the Einstein-Hilbert action. After decomposing the perturbations in spherical harmonics, we study the linearized modified field equations and find that axial and polar modes are coupled, in contrast to general relativity. The divergence of the modified equations leads to the Pontryagin constraint, which forces the vanishing of the Cunningham-Price-Moncrief master function associated with axial modes. We analyze the structure of these equations and find that the appearance of the Pontryagin constraint yields an overconstrained system that does not allow for generic black hole oscillations. We illustrate this situation by studying the case characterized by a canonical choice of the coupling function and pure-parity perturbative modes. We end with a discussion of how to extend Chern-Simons modified gravity to bypass the Pontryagin constraint and the suppression of perturbations.

Interacting quintessence models have been proposed to explain or, at least, alleviate the coincidence problem of late cosmic acceleration. In this paper we are concerned with two aspects of these kind of models: (i) the dynamical evolution of the model of Chimento et al. [L. P. Chimento, A. S. Jakubi, D. Pavón, and W. Zimdahl, Phys. Rev. D 67, 083513 (2003).], i.e., whether its cosmological evolution gives rise to a right sequence of radiation, dark matter, and dark energy–dominated eras, and (ii) whether the dark matter dark energy ratio asymptotically evolves towards a nonzero constant. After showing that the model correctly reproduces these eras, we correlate three data sets that constrain the interaction at three redshift epochs: $z\le {10}^4$, $z={10}^3$, and $z=1$. We discuss the model selection and argue that even if the model under consideration fulfills both requirements, it is heavily constrained by observation. The prospects that the coincidence problem can be explained by the coupling of dark matter to dark energy are not clearly favored by the data.

The GLAST satellite mission will study the gamma ray sky with considerably greater exposure than its predecessor EGRET. In addition, it will be capable of measuring the arrival directions of gamma rays with much greater precision. These features each significantly enhance GLAST’s potential for identifying gamma rays produced in the annihilations of dark matter particles. The combined use of spectral and angular information, however, is essential if the full sensitivity of GLAST to dark matter is to be exploited. In this paper, we discuss the separation of dark matter annihilation products from astrophysical backgrounds, focusing on the galactic center region, and perform a forecast for such an analysis. We consider both pointlike and diffuse astrophysical backgrounds and model them using a point-spread-function for GLAST. While the results of our study depend on the specific characteristics of the dark matter signal and astrophysical backgrounds, we find that in many scenarios it is possible to successfully identify dark matter annihilation radiation, even in the presence of significant astrophysical backgrounds.

This is the second paper in the series that confronts predictions of a model of the landscape with cosmological observations. We show here how the modifications of the Friedmann equation due to the decohering effects of long wavelength modes on the wave function of the Universe defined on the landscape leave unique signatures on the CMB spectra and large scale structure (LSS). We show that the effect of the string corrections is to suppress ${\sigma }_8$ and the CMB temperature-temperature (TT) spectrum at large angles, thereby bringing WMAP and SDSS data for ${\sigma }_8$ into agreement. We find interesting features imprinted on the matter power spectrum $P(k)$: power is suppressed at large scales indicating the possibility of primordial voids competing with the integrated Sachs-Wolfe effect. Furthermore, power is enhanced at structure and substructure scales, $k\simeq {10}^{-2-0}h{\mathrm{Mpc}}^{-1}$. Our smoking gun for discriminating this proposal from others with similar CMB and LSS predictions comes from correlations between cosmic shear and temperature anisotropies, which here indicate a noninflationary channel of contribution to LSS, with unique ringing features of nonlocal entanglement displayed at structure and substructure scales.

We investigate the effects of quantum entanglement between our horizon patch and others due to the tracing out of long wavelength modes in the wave function of the Universe as defined on a particular model of the landscape. In this, the first of two papers devoted to this topic, we find that the SUSY breaking scale is bounded both above and below: ${10}^{-10}{M}_{\mathrm{P}}\le M_{\mathrm{SUSY}}\le {10}^{-8}{M}_{\mathrm{P}}$ for grand unified theory (GUT) scale inflation. Bounds on the SUSY breaking parameter depend on the scale of inflation. If inflation occurred at GUT energies, the lower bound on $b$ is at least 5 orders of magnitude larger than the expected value of this parameter, soon to be tested by LHC.

I consider a (long-lived) sterile neutrino dark matter scenario in a five dimensional (5D) warped extra dimension model where the fields can live in the bulk, which is partly motivated from the absence of the absolutely stable particles in a simple Randall-Sundrum model. The dominant production of the sterile neutrino can come from the decay of the radion (the scalar field representing the brane separation) around the electroweak scale. The suppressions of the 4D parameters due to the warp factor and the small wave function overlaps in the extra dimension help alleviate the exceeding fine-tunings typical for a sterile neutrino dark matter scenario in a 4D setup.

The picture of the “multiverse” arising in diverse cosmological scenarios involves transitions between metastable vacuum states. It was pointed out by Krauss and Dent that the transition rates decrease at very late times, leading to a dependence of the transition probability between vacua on the age of each vacuum region. I investigate the implications of this non-Markovian, age-dependent decay on the global structure of the spacetime in landscape scenarios. I show that the fractal dimension of the eternally inflating domain is precisely equal to 3, instead of being slightly below 3, which is the case in scenarios with purely Markovian, age-independent decay. I develop a complete description of a non-Markovian landscape in terms of a nonlocal master equation. Using this description I demonstrate by an explicit calculation that, under some technical assumptions about the landscape, the probabilistic predictions of our position in the landscape are essentially unchanged, regardless of the measure used to extract these predictions. I briefly discuss the physical plausibility of realizing non-Markovian vacuum decay in cosmology in view of the possible decoherence of the metastable quantum state.

The couplings of charmonia and charmonium hybrids (generically $\Psi$) to $p\overline{p}$ are of great interest in view of future plans to study these states using an antiproton storage ring at GSI. These low to moderate energy $\Psi p\overline{p}$ couplings are not well understood theoretically, and currently must be determined from experiment. In this paper we note that the two independent Dirac (${\gamma }_{\mu }$) and Pauli (${\sigma }_{\mu \nu }$) $p\overline{p}$ couplings of the $J/\psi$ and ${\psi }^{\prime }$ can be constrained by the angular distribution of $e^{+}{e}^{-}\to (J/\psi ,{\psi }^{\prime })\to p\overline{p}$ on resonance. A comparison of our theoretical results to recent unpolarized data allows estimates of the $p\overline{p}$ couplings; in the better determined $J/\psi$ case the data is inconsistent with a pure Dirac (${\gamma }_{\mu }$) coupling, and can be explained by the presence of a ${\sigma }_{\mu \nu }$ term. This Pauli coupling may significantly affect the cross section of the PANDA process $p\overline{p}\to {\pi }^{0}J/\psi$ near threshold. There is a phase ambiguity that makes it impossible to uniquely determine the magnitudes and relative phase of the Dirac and Pauli couplings from the unpolarized angular distributions alone; we show in detail how this can be resolved through a study of the polarized reactions.

We propose and discuss the phenomenology of a topcolor-assisted technicolor model with a flavor-universal hypercharge sector. After discussing the symmetry-breaking pattern and low-energy effective Lagrangian, we examine various experimental and theoretical constraints, finding that precision electroweak measurements yield the strongest bounds on the model. We perform a combined fit to all available $Z$-pole and LEP2 data and find that the goodness of fit for hypercharge-universal topcolor is comparable to that of the standard model. In contrast, topcolor-assisted technicolor models with a flavor nonuniversal hypercharge sector are markedly disfavored by the data.

We present results of a calculation of the cross section for the production of a charged Higgs boson in association with an electron and a neutrino at electron-positron colliders ($e^{+}{e}^{-}\to H^{+}{e}^{-}{\overline{\nu }}_e$, $H^{-}{e}^{+}{\nu }_e$). We study predictions for the cross section in the minimal supersymmetric standard model (MSSM) and the two Higgs doublet model (THDM), highlighting possible differences. The process is effectively loop-induced in both models. Hence, the cross section is expected to be strongly model-dependent. Most notably, due to the presence of superpartners, the MSSM amplitude contains Feynman graphs of pentagon-type, which are not present in the THDM. This is the first complete one-loop calculation of the cross section for this process in the THDM and the MSSM. For both models, so far, only approximate results with limited ranges of validity were available. Our main aim here is to clarify several open questions in the existing literature on this process. Specifically, we will discuss the validity of the heavy fermion loop approximation in both models, and of the fermion/sfermion loop approximation in the MSSM.

We classify ${\Lambda }_{\mathrm{QCD}}/m_b$ power corrections to nonleptonic $B\to M_1{M}_2$ decays, where $M_{1,2}$ are charmless nonisosinglet mesons. Using recent developments in soft-collinear effective theory, we prove that the leading contributions to annihilation amplitudes of order ${\alpha }_s(m_b){\Lambda }_{\mathrm{QCD}}/m_b$ are real. The leading annihilation amplitudes depend on twist-2 and twist-3 three-parton distributions. A complex nonperturbative parameter from annihilation first appears at $\mathcal{O}[{\alpha }_s^2(\sqrt{\Lambda m_b}){\Lambda }_{\mathrm{QCD}}/m_b]$. “Chirally enhanced” contributions are also factorizable and real at lowest order. Thus, incalculable strong phases are suppressed in annihilation amplitudes, unless the ${\alpha }_s(\sqrt{\Lambda m_b})$ expansion breaks down. Modeling the distribution functions, we find that $(11\pm 9)\%$ and $(15\pm 11)\%$ of the absolute values of the measured ${\overline{B}}^0\to K^{-}{\pi }^{+}$ and $B^{-}\to K^{-}{K}^0$ penguin amplitudes come from annihilation. This is consistent with the expected size of power corrections.

This paper serves as a report on the large amount of analysis done in conjunction with the polarized proton program at the Relavitistic Heavy Ion Collider at Brookhaven National Laboratory. This comprises elastic scattering data of protons on protons in colliding beam or fixed target mode and proton beams on carbon targets. In addition to providing a model for the energy dependence of the analyzing power of elastic scattering needed for proton polarimetry, it also provides some significant information about the spin dependence of dominant Regge poles. Most notably, the data indicate that the Pomeron has a significant spin-flip coupling. This allows the exploration of the double-spin flip asymmetry $A_{NN}$ for which some data over a wide energy range are now available, along with a concrete realization of a proposed Odderon search.

Different approaches to take into account nonzero lepton mass effects in the Rein-Sehgal model are compared. Modification of the axial current due to a pion pole term is included, and it is shown that it leads to large reduction of the antineutrino cross section and a change of the shape of $d\sigma /d{Q}^2$.

We give a perturbation theory of neutrino oscillation in the Earth. The perturbation theory is valid for neutrinos with energy $E\gtrsim 0.5\mathrm{GeV}$. It is formulated using trajectory dependent average potential. Nonadiabatic contributions are included as the first order effects in the perturbation theory. We analyze neutrino oscillation with standard matter effect and with nonstandard matter effect. In a three flavor analysis we show that the perturbation theory gives a precise description of neutrino conversion in the Earth. The effect of the Earth matter is substantially simplified in this formulation.