We investigate the critical end point of QCD with two flavours of light dynamical quarks at finite lattice cutoff $a=1/4T$ using a Taylor expansion of the baryon number susceptibility. We find a strong volume dependence of its radius of convergence. In the large volume limit we obtain ${\mu }_B/T\approx 1.1$ as the radius of convergence at $T/T_c\approx 0.95$ where $T_c$ is the crossover temperature at zero chemical potential. Since this estimate is a lower bound on the critical end point of QCD, the above small value of $\mu$ may place it in the range of observability in energy scans at the Relativistic Heavy-Ion Collider (RHIC).

We analyze the effect of the nonuniversal $Z$ boson in the rare decays $B_s\to l^{+}{l}^{-}$, $B_s\to l^{+}{l}^{-}\gamma$, and $Z\to b\overline{s}$ decays. These decays involve the flavor changing neutral current (FCNC) mediated $b\to s$ transitions, and are found to be very small in the standard model. The smallness of these decays in the standard model makes them sensitive probe for new physics. We find an enhancement of at least an order in these branching ratios because of the nonuniversal $Zbs$ coupling.

We obtain the exact solution of the Klein-Gordon equation describing the propagation of a particle in two regions of different constant magnetic field, separated by an infinite plane wall. The continuity of the wave function and of its derivative at the interface is satisfied when including evanescent-wave terms. We analyze solutions on truncated spaces and compare them with previously obtained approximate solutions. The findings of this work have applications in the problem of the propagation of particles in the presence of a bubble wall in the midsts of an electroweak phase transition, where the two regions separated by the wall are influenced by different (hyper)magnetic-field strengths.

I propose a model, in the framework of five dimensions with warped geometry, in which small neutrino Majorana masses are generated by tree-level coupling of lepton doublets to a $SU(2{)}_L$-triplet scalar field, which is coupled to a bulk standard model singlet. The neutrino mass scale is determined by the bulk mass term $({\alpha }_S)$ of the singlet as $v{e}^{-2({\alpha }_S-1)\pi kR}$. This suppression is due to a small overlap between the profile of the singlet zero mode and the triplet, which is confined to the TeV brane. The generic form for the neutrino mass matrix due to the overlap between the fermions is not compatible with the large mixing angle solution. This is overcome by imposing a $Z_4$ symmetry, which is softly broken by couplings of the triplet Higgs to the lepton doublets. This model successfully reproduces the observed masses and mixing angles in the charged lepton sector as well as in the neutrino sector, in addition to having a prediction of $|U_{e3}|\sim \mathcal{O}(0.01)$. The mass of the triplet is of the order of a TeV and could be produced at upcoming collider experiments. The doubly charged member of the triplet can decay into two same sign charged leptons, yielding the whole triplet coupling matrix which, in turn, gives the mixing matrix in the neutrino sector.

It is shown that the recently claimed two new Brans-Dicke wormhole solutions [F. He and S-W. Kim, Phys. Rev. D 65, 084022 (2002)] are not really new solutions. They are just the well known Brans-Dicke solutions of Class I and II in a different conformal gauge.

Eccentricities of the mass center from the geometric center of two cylindrical source masses used in the HUST-99 measurement of the Newtonian gravitational constant $G$ are determined by means of an electronic balance. Considering a linear density distribution of source masses as well as the effect of the air buoyancy, our value of $G$ should be revised to be $6.6723(9)\times {10}^{-11}{\mathrm{m}}^3{\mathrm{kg}}^{-1}{\mathrm{s}}^{-2}$, which is 0.036% larger than our previous published value in Phys. Rev. D 59, 042001 (1999).

Gregory and Laflamme (hep-th/9301052) have argued that an instability causes the Schwarzschild black string to break up into disjoint black holes. On the other hand, Horowitz and Maeda (arXiv:hep-th/0105111) derived bounds on the rate at which the smallest sphere can pinch off, showing that, if it happens at all, such a pinch-off can occur only at infinite affine parameter along the horizon. An interesting point is that, if a singularity forms, such an infinite affine parameter may correspond to a finite advanced time—which is in fact a more appropriate notion of time at infinity. We argue below that pinch-off at a finite advanced time is in fact a natural expectation under the bounds derived by Horowitz and Maeda.

We reanalyze the question of black hole creation in high energy scattering via shock wave collisions. We find that string corrections tend to increase the scattering cross section. We analyze corrections in a more physical setting, of Randall-Sundrum type and of higher dimensionality. We also analyze the scattering inside anti–de Sitter backgrounds.

We study the dynamics of a bounded collapsing configuration emitting gravitational waves, whose exterior spacetime is described by the Robinson-Trautman metric. In this process mass is lost due to gravitational wave emission until the Schwarzschild black hole is formed. By performing a careful computation of the distribution of the mass fraction extracted by gravitational radiation, we have shown that it satisfies the distribution law of Tsallis nonextensive statistics, and this result is independent of the initial data considered.

We investigate highly damped quasinormal modes of regular black hole coupled to nonlinear electrodynamics. Using the WKB approximation combined with complex-integration technique, we show that the real part of the frequency disappears in the highly damped limit. If we use the Bohr’s correspondence principle, the area spectrum of this black hole is continuous. We discuss its implications for loop quantum gravity.

The inelastic scattering of the brane fields induced by $t$-channel gravi-Reggeons exchanges in the Randall-Sundrum (RS) model with a small curvature $\kappa$ is considered, and the imaginary part of the eikonal is analytically calculated. It is demonstrated that the results can be obtained from the corresponding formulae previously derived in the Arkani-Hamed—Dimopoulos—Dvali (ADD) model with one extra dimension of the size $R_c$ by formal replacement $R_c\to (\pi \kappa {)}^{-1}$. The inelastic cross section for the scattering of ultrahigh neutrino off the nucleon is numerically estimated for the case $\kappa \ll {\overline{M}}_5\sim 1\mathrm{TeV}$, where ${\overline{M}}_5$ is a reduced Planck scale in five warped dimensions.

We study here the effect of a varying $G$ on the evolution of the early Universe and, in particular, on primordial nucleosynthesis. This variation of $G$ is modeled using the Brans-Dicke theory as well as a more general class of scalar-tensor theories. Modified nucleosynthesis codes are used to investigate this effect and the results obtained are used to constrain the parameters of the theories. We extend previous studies of primordial nucleosynthesis in scalar-tensor theories by including effects which can cause a slow variation of $G$ during radiation domination and by including a late-time accelerating phase to the Universe’s history. We include a brief discussion on the epoch of matter-radiation equality in Brans-Dicke theory, which is also of interest for determining the positions of the cosmic microwave background power-spectrum peaks.

In this work on the basis of Kadomtsev’s kinetic fluctuation theory we present the more general expression for noise-noise correlation function in effective theory for ultrasoft field modes.

The presence of the top-pions ${\pi }_t^{0,\pm }$ in the low-energy spectrum is an inevitable feature of the topcolor scenario. Taking into account the constraints of the present experimental limit of the lepton flavor violating (LFV) process $\mu \to e\gamma$ on the free parameters of topcolor-assisted technicolor models, we study the contributions of the neutral top-pion ${\pi }_t^0$ to the LFV processes ${\mu }^{+}{\mu }^{-}\to \tau \mu$ (or $\tau e$), $\gamma \gamma \to \tau \mu$ (or $\tau e$), $e^{+}{e}^{-}\to \tau \mu$, and $e\gamma \to e{\pi }_t^0\to e\tau \mu (e)$ via the flavor changing couplings ${\pi }_t^0{l}_i{l}_j$ and discuss the possibility of searching for the LFV signals via these processes in future lepton colliders.

We investigate $\Lambda (1520,3/2^{-},D_{03})$ photoproduction via the $\gamma N\to K{\Lambda }^{*}$ process. Using effective Lagrangians, we compute the total and differential cross sections. The dependence on the momentum transfer for the photoproduction at the tree-level is also examined. We find that the total cross sections for the proton target are well reproduced as compared with the experimental data. It turns out that the total cross sections for the neutron target are significantly smaller than those for the proton one. We also compare the present results with the $\gamma N\to \overline{K}{\Theta }^{+}$ reaction in order to extract information of ${\Theta }^{+}$. The role of $K^{*}$-exchange in the production reaction is also discussed.

The gapless color-flavor locked (gCFL) phase is a candidate for the second-densest phase of matter in the QCD phase diagram, making it a plausible constituent of the core of neutron stars. We show that even a relatively small region of gCFL matter in a star will dominate both the heat capacity $C_V$ and the heat loss by neutrino emission $L_{\nu }$. The gCFL phase is characterized by an unusual quasiparticle dispersion relation that makes both its specific heat $c_V$ and its neutrino emissivity ${\epsilon }_{\nu }$ parametrically larger than in any other phase of nuclear or quark matter. During the epoch in which the cooling of the star is dominated by direct Urca neutrino emission, the presence of a gCFL region does not strongly alter the cooling history because the enhancements of $C_V$ and $L_{\nu }$ cancel against each other. At late times, however, the cooling is dominated by photon emission from the surface, so $L_{\nu }$ is irrelevant, and the anomalously large heat capacity of the gCFL region keeps the star warm. The temperature drops with time as $T\sim t^{-1.4}$ rather than the canonical $T\sim t^{-5}$. This provides a unique and potentially observable signature of gCFL quark matter.

This work is devoted to the study of diquark correlations inside the nucleon. We analyze some matrix elements which encode information about the nonperturbative forces, in different color antitriplet diquark channels. We suggest a lattice calculation to check the quark-diquark picture and clarify the role of instanton-mediated interactions. We study in detail the physical properties of the $0^{+}$ diquark, using the random instanton liquid model. We find that instanton forces are sufficiently strong to form a diquark bound state, with a mass of $\sim 500\mathrm{MeV}$, which is compatible with earlier estimates. We also compute its electromagnetic form factor and find that the diquark is a broad object, with a size comparable with that of the proton.

In the minimal supersymmetric standard model extended by including right-handed neutrinos with seesaw mechanism, the neutrino Yukaka couplings can be as large as the top-quark Yukawa couplings and thus the neutrino/sneutrino may cause sizable effects in Higgs boson self-energy loops. Our explicit one-loop calculations show that the neutrino/sneutrino effects may have an opposite sign to top/stop effects and thus lighten the lightest Higgs boson. If the soft-breaking mass of the right-handed neutrino is very large (at the order of Majorana mass scale), such as in the split-supersymmetry (SUSY) scenario, the effects can lower the lightest Higgs boson mass by a few tens of GeV. So the Higgs mass bound of about 150 GeV in split-SUSY may be lowered significantly if right-handed neutrinos come into play with seesaw mechanism.

The phase diagram of the three-flavor QCD is mapped out in the low mass corner of the ($m_{\pi }-m_K$)-plane with help of the $S{U}_L(3)\times S{U}_R(3)$ linear sigma model ($L\sigma M$). A novel zero temperature parametrization is proposed for the mass dependence of the couplings away from the physical point based on the three-flavor chiral perturbation theory (U(3) ChPT). One-loop thermodynamics is constructed by applying optimized perturbation theory. The unknown dependence of the scalar spectra on the pseudoscalar masses limits the accuracy of the predictions. Results are compared to lattice data and similar investigations with other variants of effective chiral models. The critical value of the pion mass is below 65 MeV for all $m_K$ values $\lesssim 800\mathrm{MeV}$. Along the diagonal $m_{\pi }=m_K$, we estimate $m_{\mathrm{crit}}(\mathrm{diag})=40\pm 20\mathrm{MeV}$.

We construct smooth nonsupersymmetric soliton solutions with D1-brane, D5-brane, and momentum charges in type IIB supergravity compactified on $T^4\times S^1$, with the charges along the compact directions. This generalizes previous studies of smooth supersymmetric solutions. The solutions are obtained by considering a known family of $U(1)\times U(1)$ invariant metrics, and studying the conditions imposed by requiring smoothness. We discuss the relation of our solutions to states in the CFT describing the D1-D5 system and describe various interesting features of the geometry.