The growth and virialization of spherical top-hat fluctuations, in coupled dark energy models, causes segregation between dark matter (DM) and baryons, as the gravitational infall into the potential well proceeds more slowly for the baryons than for DM. As a consequence, after attaining their turnaround and before full virialization, halos have outer layers rich of baryons. Accordingly, a natural ambiguity exists on the definition of the virial density contrast. In fact, when the outer baryon layers infall onto the DM-richer core, they carry with them DM materials outside the original fluctuation; hence, no time exists when all materials originally belonging to the fluctuation—and only they—have virialized. Baryon-DM segregation can have various astrophysical consequences on different length scales. The smallest halos may loose up to 50% of the original baryonic contents and become hardly visible. Subhalos in cluster-size halos may loose much baryonic materials, which could then be observed as intracluster light. Isolated halos, in general, can be expected to have a baryon component richer than the cosmological proportions, due to the cosmic enrichement of baryons lost in small halo encounters.

Although a simple argument implies that the distribution of dark matter in galactic halos is characterized by discrete flows and caustics, their presence is often ignored in discussions of galactic dynamics and of dark matter detection strategies. Discrete flows and caustics can in fact be irrelevant if the number of flows is very large. We estimate the number of dark matter flows as a function of galactocentric distance and consider the various ways in which that number can be increased, in particular, by the presence of structure on small scales (dark matter clumps) and the scattering of the flows by inhomogeneities in the matter distribution. We find that, when all complicating factors are taken into account, discrete flows and caustics in galactic halos remain a robust prediction of cold dark matter cosmology with extensive implications for observation and experiment.

The reconstruction of scalar-field dark energy models is studied for a general Lagrangian density $p(\varphi ,X)$, where $X$ is a kinematic term of a scalar-field $\varphi$. We implement the coupling $Q$ between dark energy and dark matter and express reconstruction equations using two observables: the Hubble parameter $H$ and the matter density perturbation ${\delta }_m$. This allows us to determine the structure of corresponding theoretical Lagrangian together with the coupling $Q$ from observations. We apply our formula to several forms of Lagrangian and present concrete examples of reconstruction by using the recent Gold dataset of supernovae measurements. This analysis includes a generalized ghost condensate model as a way to cross a cosmological-constant boundary even for a single-field case.

We describe an algorithm which directly determines the quintessence potential from observational data, without using an equation of state parametrization. The strategy is to numerically determine observational quantities as a function of the expansion coefficients of the quintessence potential, which are then constrained using a likelihood approach. We further impose a model selection criterion, the Bayesian Information Criterion, to determine the appropriate level of the potential expansion. In addition to the potential parameters, the present day quintessence field velocity is kept as a free parameter. Our investigation contains unusual model types, including a scalar field moving on a flat potential, or in an uphill direction, and is general enough to permit oscillating quintessence field models. We apply our method to the “gold“ Type Ia supernovae sample of Riess et al. [A. G. Riess et al. (Supernova Search Team Collaboration), Astrophys. J. 607, 665 (2004)] confirming the pure cosmological constant model as the best description of current supernovae luminosity-redshift data. Our method is optimal for extracting quintessence parameters from future data.

In split-supersymmetry (split-SUSY), gluino is a metastable particle and thus can freeze out in the early universe. The late decay of such a long-life gluino into the lightest supersymmetric particle (LSP) may provide much of the cosmic dark-matter content. In this work, assuming the LSP is gravitino produced from the late decay of the metastable gluino, we examine the Wilkinson microwave anisotropy probe (WMAP) dark-matter constraints on the gluino mass. We find that to provide the full abundance of dark matter, the gluino must be heavier than about 14 TeV and thus not accessible at the CERN large hadron collider (LHC).

A recently developed standard-model extension (SME) formalism for neutrino oscillations that includes Lorentz and $CPT$ violation is used to analyze the sidereal time variation of the neutrino event excess measured by the liquid scintillator neutrino detector (LSND) experiment. The LSND experiment, performed at Los Alamos National Laboratory, observed an excess, consistent with neutrino oscillations, of ${\overline{\nu }}_e$ in a beam of ${\overline{\nu }}_{\mu }$. It is determined that the LSND oscillation signal is consistent with no sidereal variation. However, there are several combinations of SME coefficients that describe the LSND data; both with and without sidereal variations. The scale of Lorentz and $CPT$ violation extracted from the LSND data is of order ${10}^{-19}\mathrm{GeV}$ for the SME coefficients $a_L$ and $E\times c_L$. This solution for Lorentz and $CPT$ violating neutrino oscillations may be tested by other short baseline neutrino oscillation experiments, such as the MiniBooNE experiment.

We study the possibility that charge breaking (CB) minima occur in the Zee model. We reach very different conclusions from those attained in simpler, two Higgs doublet models, and the reason for this is traced back to the existence of cubic terms in the potential. A scan of the Zee model’s parameter space shows that CB is restricted to a narrow region of values of the parameters.

We study the lattice model for the supersymmetric Yang-Mills theory in two-dimensions proposed by Cohen, Kaplan, Katz, and Unsal. We re-examine the formal proof for the absence of susy-breaking counterterms as well as the stability of the vacuum by an explicit perturbative calculation for the case of $U(2)$ gauge group. Introducing fermion masses and treating the bosonic zero momentum mode nonperturbatively, we avoid the infra-red divergences in the perturbative calculation. As a result, we find that there appear mass counterterms for finite volume which vanish in the infinite volume limit so that the theory needs no fine-tuning. We also find that the supersymmetry plays an important role in stabilizing the lattice spacetime by the deconstruction.

The pion electromagnetic form factor is calculated within the QCD light-cone sum rule method and using a renormalon model for the higher twist distribution amplitudes (DAs). The theoretical predictions are compared with the experimental data and constraints on the pion leading and twist-4 DAs are extracted. An upper bound on the twist-4 contribution to the form factor and estimates of effects due to higher conformal spins in the pion twist-4 DAs are obtained.

In this paper the production of excited vector and pseudoscalar charmonium mesons in $e^{+}{e}^{-}$ annihilation is analyzed in the framework of the light cone. In particular the cross sections $e^{+}{e}^{-}\to \psi (2S){\eta }_c(1S),\psi (1S){\eta }_c(2S),\psi (2S){\eta }_c(2S)$ have been calculated. It is shown that contrary to NRQCD, the cross sections calculated in the framework of the light cone agree with experimental data.

We study the effect of random magnetic fields in the spin-flavor precession of solar neutrinos in a three generation context, when a nonvanishing transition magnetic moment is assumed. While this kind of precession is strongly constrained when the magnetic moment involves the first family, such constraints do not apply if we suppose a transition magnetic moment between the second and third families. In this scenario we can have a large nonelectron antineutrino flux arriving on Earth, which can lead to some interesting phenomenological consequences, as, for instance, the suppression of day-night asymmetry. We have analyzed the high-energy solar neutrino data and the KamLAND experiment to constrain the solar mixing angle, ${\theta }_{\odot }$, and solar mass difference, $\Delta m_{\odot }^2$, and we have found a large shift of allowed values. Also, sizable effects in the Borexino experiment are expected which can discriminate this scenario and standard large mixing angle solution to the solar neutrino problem.

A search for the direct production of Higgs bosons in the di-tau decay mode is performed with $86.3\pm 3.5{\mathrm{pb}}^{-1}$ of data collected with the Collider Detector at Fermilab during the 1994–1995 data taking period of the Tevatron. We search for events where one tau decays to an electron plus neutrinos and the other tau decays hadronically. We perform a counting experiment and set limits on the cross section for supersymmetric Higgs boson production where $\tan \beta$ is large and $m_A$ is small. For a benchmark parameter space point where $m_{A^0}=100\mathrm{GeV}/c^2$ and $\tan \beta =50$, we limit the production cross section multiplied by the branching ratio to be less than 77.9 pb at the 95% confidence level compared to the theoretically predicted value of 11.0 pb. This is the first search for Higgs bosons decaying to tau pairs at a hadron collider.

We report the observation of the decay $B^{-}\to D_{{\pi }^{+}{\pi }^{-}{\pi }^0}{K}^{-}$, where $D_{{\pi }^{+}{\pi }^{-}{\pi }^0}$ indicates a neutral $D$ meson detected in the final state ${\pi }^{+}{\pi }^{-}{\pi }^0$, excluding $K_S^0{\pi }^0$. This doubly Cabibbo-suppressed decay chain can be used to measure the CKM phase $\gamma$. Using about $229\times {10}^6$ $e^{+}{e}^{-}\to B\overline{B}$ events recorded by the BABAR experiment at the PEP-II $e^{+}{e}^{-}$ storage ring, we measure the branching fraction $\mathcal{B}(B^{-}\to D_{{\pi }^{+}{\pi }^{-}{\pi }^0}{K}^{-})=(5.5\pm 1.0(\mathrm{stat}.)\pm 0.7(\mathrm{syst}.))\times {10}^{-6}$ and the decay rate asymmetry $A(B^{-}\to D_{{\pi }^{+}{\pi }^{-}{\pi }^0}{K}^{-})=-0.02\pm 0.16(\mathrm{stat}.)\pm 0.03(\mathrm{syst}.)$ for the full decay chain.

We propose a new scenario of nonthermal production of neutralino cold dark matter, in which the overproduction problem of lightest supersymmetric particles (LSPs) in the standard thermal history is naturally solved. The mechanism requires a heavy modulus field which decays mainly to ordinary particles releasing large entropy to dilute gravitinos produced just after inflation and thermal relics of LSPs. Significant amount of gravitinos are also pair-produced at the decay, which subsequently decay into the neutralinos. We identify the regions of the parameter space in which the requisite abundance of the neutralino dark matter is obtained without spoiling the big-bang nucleosynthesis by injection of hadronic showers from gravitino decay. The neutralino abundance obtained in this mechanism is insensitive to the details of the superparticle mass spectrum, unlike the standard thermal abundance. We also briefly mention the testability of the scenario in future experiments.

We calculated the next-to-leading order (NLO) QCD corrections to the cross sections for direct top quark productions induced by model-independent flavor-changing neutral current couplings at hadron colliders. The NLO results increase the experimental sensitivity to the anomalous couplings. Our results show that the NLO QCD corrections enhance the leading order (LO) total cross sections at the Tevatron Run 2 about $60\%$ for both ${\kappa }_{tc}^g$ and ${\kappa }_{tu}^g$ couplings, and enhance the LO total cross sections at the LHC about $40\%$ for ${\kappa }_{tc}^g$ couplings and $50\%$ for ${\kappa }_{tu}^g$ couplings, respectively. Moreover, the NLO QCD corrections vastly reduce the dependence of the total cross sections on the renormalization or factorization scale, which leads to increased confidence in predictions based on these results.

We provide an analytic solution to the short wave length limit of the integro-differential equation describing the damping of the tensor modes of gravitational waves.

We consider the mirage cosmology by an unstable probe brane whose action is represented by Dirac-Born-Infeld action with tachyon. We study how the presence of tachyon affects the evolution of the brane inflation. At the early stage of the brane inflation, the tachyon kinetic term can play an important role in curing the superluminal expansion in mirage cosmology.

Within the axiomatic premetric approach to classical electrodynamics, we derive under which covariant conditions the quartic Fresnel surface represents a unique light cone without birefringence in vacuum.

Quasinormal frequencies of electromagnetic and gravitational perturbations in asymptotically anti-de Sitter spacetime can be identified with poles of the corresponding real-time Green’s functions in a holographically dual finite temperature field theory. The quasinormal modes are defined for gauge-invariant quantities which obey an incoming-wave boundary condition at the horizon and a Dirichlet condition at the boundary. As an application, we explicitly find poles of retarded correlation functions of $R$-symmetry currents and the energy-momentum tensor in strongly coupled finite temperature $\mathcal{N}=4$ supersymmetric $SU(N_c)$ Yang-Mills theory in the limit of large $N_c$.