We explore the possible signatures of dark matter pair annihilations in the nearby dwarf spheroidal galaxy Draco. After investigating the mass models for Draco in the light of available observational data, we carefully model the dark matter density profile, taking advantage of numerical simulations of hierarchical structure formation. We then analyze the gamma-ray and electron/positron yield expected for weakly interacting dark matter particle (WIMP) models, including an accurate treatment of the propagation of the charged particle species. We show that unlike in larger dark matter structures—such as galaxy clusters—spatial diffusion plays here an important role. While Draco would appear as a pointlike gamma-ray source, synchrotron emission from electrons and positrons produced by WIMP annihilations features a spatially extended structure. Depending upon the cosmic ray propagation setup and the size of the magnetic fields, the search for a diffuse radio emission from Draco can be a more sensitive indirect dark matter search probe than gamma rays. Finally, we show that available data are consistent with the presence of a black hole at the center of Draco: if this is indeed the case, very significant enhancements of the rates for gamma rays and other emissions related to dark matter annihilations are expected.

We propose a simple power-law parametrized quintessence model with time-varying equation of state and obtain corresponding quintessence potential of this model. This model is compared with Supernova Type Ia (SNIa) Gold sample data, size of baryonic acoustic peak from Sloan Digital Sky Survey (SDSS), the position of the acoustic peak from the CMB observations and structure formation from the 2dFGRS survey and put constrain on the parameters of model. The parameters from the best fit indicates that the equation of state of this model at the present time is $w_0=-{1.40}_{-0.65}^{+0.40}$ at $1\sigma$ confidence level. Finally we calculate the age of universe in this model and compare it with the age of old cosmological objects.

In the theoretical framework of the minimal supersymmetric extension of the standard model (MSSM), we study the pair production of heavy charged and neutral Higgs bosons in $e^{+}{e}^{-}$ collisions with a center-of-mass energy of 3 TeV, at the Compact Linear Collider (CLIC). The high-energy beam-beam effects at the interaction point are taken into account in our simulations. With an integrated luminosity of $3000{\mathrm{fb}}^{-1}$, the hadronic cascade decays of $H^{+}{H}^{-}$ and $A^0{H}^0$ pairs can be observed over a wide range of Higgs boson masses, extending beyond 1 TeV. The Higgs mass parameter $m_A$ can be derived from a ${\chi }^2$-analysis, and the corresponding statistical error was found to be smaller than 1%. In addition, by comparing the signal rates of different decay channels, one can determine the ratio between the vacuum expectation values $\tan \beta$ with a good accuracy in the intermediate region, i.e. when $\tan \beta$ lies between 6 and 11 typically.

We study the phase diagram of quark matter at finite temperature ($T$) and chemical potential ($\mu$) in the strong coupling limit of lattice QCD for color SU(3). We derive an analytical expression of the effective free energy as a function of $T$ and $\mu$, including baryon effects. The finite temperature effects are evaluated by integrating over the temporal link variable exactly in the Polyakov gauge with an antiperiodic boundary condition for fermions. The obtained phase diagram shows the first and the second order phase transition at low and high temperatures, respectively, and those are separated by the tricritical point in the chiral limit. Baryon has effects to reduce the effective free energy and to extend the hadron phase to a larger $\mu$ direction at low temperatures.

We analyze the azimuthal dependence of the heavy-quark-initiated contributions to the lepton-nucleon deep inelastic scattering (DIS). First we derive the relations between the parton-level semi-inclusive structure functions and the helicity ${\gamma }^{*}Q$ cross sections in the case of arbitrary values of the heavy quark mass. Then the azimuth-dependent $\mathcal{O}({\alpha }_s)$ lepton-quark DIS is calculated in the helicity basis. Finally, we investigate numerically the properties of the $\cos \phi$ and $\cos 2\phi$ distributions caused by the photon-quark scattering (QS) contribution. It turns out that, contrary to the basic photon-gluon fusion (GF) component, the QS mechanism is practically $\cos 2\phi$-independent. This fact implies that measurements of the azimuthal distributions in charm leptoproduction could directly probe the charm density in the proton.

In this paper, we investigate phenomenologically several weak decays of charmed mesons emitting a pseudoscalar meson and an axial-vector meson. Decay amplitudes are obtained using the factorization scheme in the spectator quark model. Branching ratios for the Cabibbo angle-favored, Cabibbo angle-suppressed, and Cabibbo angle-doubly-suppressed decays are obtained and compared with available experimental results.

The $\mathcal{O}(\alpha )$ virtual weak radiative corrections to many hadron collider processes are known to become large and negative at high energies, due to the appearance of Sudakov-like logarithms. At the same order in perturbation theory, weak boson emission diagrams contribute. Since the $W$ and $Z$ bosons are massive, the $\mathcal{O}(\alpha )$ virtual weak radiative corrections and the contributions from weak boson emission are separately finite. Thus, unlike in QED or QCD calculations, there is no technical reason for including gauge boson emission diagrams in calculations of electroweak radiative corrections. In most calculations of the $\mathcal{O}(\alpha )$ electroweak radiative corrections, weak boson emission diagrams are therefore not taken into account. Another reason for not including these diagrams is that they lead to final states which differ from that of the original process. However, in experiment, one usually considers partially inclusive final states. Weak boson emission diagrams thus should be included in calculations of electroweak radiative corrections. In this paper, I examine the role of weak boson emission in those processes at the Fermilab Tevatron and the CERN LHC for which the one-loop electroweak radiative corrections are known to become large at high energies (inclusive jet, isolated photon, $Z+1$ jet, Drell-Yan, di-boson, $\overline{t}t$, and single top production). In general, I find that the cross section for weak boson emission is substantial at high energies and that weak boson emission and the $\mathcal{O}(\alpha )$ virtual weak radiative corrections partially cancel.

The polarization of ${\Xi }^0$ and ${\overline{\Xi }}^0$ hyperons produced by $800\mathrm{GeV}/c$ protons on a BeO target at a fixed targeting angle of 4.8 mrad is measured by the KTeV experiment at Fermilab. Our result of 9.7% for ${\Xi }^0$ polarization shows no significant energy dependence when compared to a result obtained at $400\mathrm{GeV}/c$ production energy and at twice our targeting angle. The polarization of the ${\overline{\Xi }}^0$ is measured for the first time and found to be consistent with zero. We also examine the dependence of polarization on production $p_t$.

The branching ratio of the rare decay ${\pi }^0\to e^{+}{e}^{-}$ has been measured precisely, using the complete data set from the KTeV E799-II experiment at Fermilab. We observe 794 candidate ${\pi }^0\to e^{+}{e}^{-}$ events using $K_L\to 3{\pi }^0$ as a source of tagged ${\pi }^0$s. The expected background is $52.7\pm 11.2$ events, predominantly from high $e^{+}{e}^{-}$ mass ${\pi }^0\to e^{+}{e}^{-}\gamma$ decays. We have measured $\mathrm{B}({\pi }^0\to e^{+}{e}^{-},(m_{e^{+}{e}^{-}}/m_{{\pi }^0}{)}^2>0.95)=(6.44\pm {0.25}_{\mathrm{stat}}\pm {0.22}_{\mathrm{syst}})\times {10}^{-8}$, which is above the unitary bound from ${\pi }^0\to \gamma \gamma$ and within the range of theoretical expectations from the standard model.

We develop an action formulation for the generalized Chaplygin gas (GCG). The most general form for the nonrelativistic GCG action is derived consistent with the equation of state. We also discuss a relativistic formulation for GCG by providing a detailed analysis of the Poincare algebra.

The averaged null energy condition (ANEC) requires that the average along a complete null geodesic of the projection of the stress-energy tensor onto the geodesic tangent vector can never be negative. It is sufficient to rule out many exotic phenomena in general relativity. Subject to certain conditions, we show that the ANEC can never be violated by a quantized minimally coupled free scalar field along a complete null geodesic surrounded by a tubular neighborhood in which the geometry is flat and whose intrinsic causal structure coincides with that induced from the full spacetime. In particular, the ANEC holds in flat space with boundaries, as in the Casimir effect, for geodesics which stay a finite distance away from the boundary.

The main result of the paper is a new representation for the Weyl Lagrangian (massless Dirac Lagrangian). As the dynamical variable we use the coframe, i.e. an orthonormal tetrad of covector fields. We write down a simple Lagrangian—wedge product of axial torsion with a lightlike element of the coframe—and show that variation of the resulting action with respect to the coframe produces the Weyl equation. The advantage of our approach is that it does not require the use of spinors, Pauli matrices, or covariant differentiation. The only geometric concepts we use are those of a metric, differential form, wedge product, and exterior derivative. Our result assigns a variational meaning to the tetrad representation of the Weyl equation suggested by Griffiths and Newing.

In this work we analyze, using quantum field theory at tree level, the massive scalar radiation emitted by a source in uniform circular motion in Minkowski spacetime, assuming Newtonian gravitation, and in the curved spacetime of a chargeless static black hole, assuming general relativity. the computations are performed analytically for the case of Minkowski spacetime and numerically for the case of Schwarzschild spacetime. We verify, for stable circular orbits, that the emission rate and the emitted power in Schwarzschild spacetime are smaller than the ones obtained in Minkowski spacetime assuming Newtonian gravitation. We obtain that only a small amount of the emitted radiation is absorbed by the black hole. We also verify that the difference between Schwarzschild and Minkowski cases decreases when the mass of field is increased. The amount of radiation absorbed by the black hole increases for higher values of the mass of the scalar field.

We discuss two aspects of $f(R)$ theories of gravity in metric formalism. We first study the reasons to introduce a scalar-tensor representation for these theories and the behavior of this representation in the limit to General Relativity, $f(R)\to R$. We find that the scalar-tensor representation is well behaved even in this limit. Then we work out the exact equations for spherically symmetric sources using the original $f(R)$ representation, solve the linearized equations, and compare our results with recent calculations of the literature. We observe that the linearized solutions are strongly affected by the cosmic evolution, which makes very unlikely that the cosmic speedup be due to $f(R)$ models with correcting terms relevant at low curvatures.

The first three years of observation of the Wilkinson Microwave Anisotropy Probe (WMAP) have provided the most precise data on the anisotropies of the cosmic microwave background (CMB) to date. We investigate the impact of these results and their combination with data from other astrophysical probes on cosmological models with a dynamical dark energy component. By considering a wide range of such models, we find that the constraints on dynamical dark energy are significantly improved compared to the first year data.

We study scalar mode perturbations (magnetosonic waves) induced by a helical stochastic cosmological magnetic field and derive analytically the corresponding cosmic microwave background (CMB) temperature and polarization anisotropy angular power spectra. We show that the presence of a stochastic magnetic field, or an homogeneous magnetic field, influences the acoustic oscillation pattern of the CMB anisotropy power spectrum, effectively acting as a reduction of the baryon fraction. We find that the scalar magnetic energy density perturbation contribution to the CMB temperature anisotropy is small compared to the contribution to the CMB $E$-polarization anisotropy.

We present an example of a realistic Higgsless model that makes use of alternative $SU(2{)}_R$ assignments for the top and bottom quarks recently proposed by Agashe et al. which results in an enhanced custodial symmetry. Using these new representations reduces the deviations in the $Z{b}_{\ell }{\overline{b}}_{\ell }$ coupling to $\sim 4\%$ for a wide range of parameters, while this remaining correction can also be eliminated by varying the localization parameter (bulk mass) for $b_r$.

Using $5.63{\mathrm{pb}}^{-1}$ of data accumulated at the $\psi (2S)$ resonance with the CLEO III and CLEO-c detectors corresponding to $3.08\times {10}^6$ $\psi (2S)$ decays, a search is performed for the decay $\psi (2S)\to {\eta }_c{\pi }^{+}{\pi }^{-}{\pi }^0$ to test a theoretical prediction based upon the assumption that the $c\overline{c}$ pair in the $\psi (2S)$ does not annihilate directly into three gluons but rather survives before annihilating. No signal is observed, and a combined upper limit from six ${\eta }_c$ decay modes is determined to be $\mathcal{B}(\psi (2S)\to {\eta }_c{\pi }^{+}{\pi }^{-}{\pi }^0)\le 1.0\times {10}^{-3}$ at 90% C.L. This upper limit is about an order of magnitude below the theoretical expectation.

We reconsider the original model of quadratic hybrid inflation in light of the WMAP three-year results and study the possibility of obtaining a spectral index of primordial density perturbations, $n_s$, smaller than 1 from this model. The original hybrid inflation model naturally predicts $n_s\ge 1$ in the false vacuum dominated regime but it is also possible to have $n_s<1$ when the quadratic term dominates. We therefore investigate whether there is also an intermediate regime compatible with the latest constraints, where the scalar field value during the last 50 e-folds of inflation is less than the Planck scale.

A simple example is used to show that renormalization group limit cycles of effective quantum theories can be studied in a new way. The method is based on the similarity renormalization group procedure for Hamiltonians. The example contains a logarithmic ultraviolet divergence that is generated by both real and imaginary parts of the Hamiltonian matrix elements. Discussion of the example includes a connection between asymptotic freedom with one scale of bound states and the limit cycle with an entire hierarchy of bound states.