Interactions of Charmed Mesons with Light Pseudoscalar Mesons from Lattice QCD and Implications on the Nature of the $D_{s0}^*(2317)$
We study the scattering of charmed mesons (D, D{sub s}) with light pseudoscalar mesons ({pi}, K) in full lattice QCD. The S-wave scattering lengths are calculated using L{umlt u}schers finite volume technique. We use the relativistic Fermilab formulation for the charm quark. For the light quark, we use domain-wall fermions in the valence sector and improved Kogut-Susskind sea quarks. We calculate the scattering lengths of isospin-3/2 D{pi}, D{sub s}{pi}, D{sub s}K, isospin-0 D{anti K} and isospin-1 D{anti K} channels on the lattice. For the chiral extrapolation, we use the chiral unitary approach to next-to-leading order, which at the same time allows us to give predictions for other channels. Furthermore, the hadronic molecular interpretation of the D{sub s0}*(2317) is consistent with our results. The isospin breaking decay width {Gamma}(D{sub s0}*(2317){yields}D{sub s}{pi}) in the hadronic molecular picture is updated to be (89{+-}22)keV.

title: Interactions of Charmed Mesons with Light Pseudoscalar Mesons from Lattice QCD and Implications on the Nature of the $D_{s0}^*(2317)$
abstract: We study the scattering of charmed mesons (D, D{sub s}) with light pseudoscalar mesons ({pi}, K) in full lattice QCD. The S-wave scattering lengths are calculated using L{umlt u}schers finite volume technique. We use the relativistic Fermilab formulation for the charm quark. For the light quark, we use domain-wall fermions in the valence sector and improved Kogut-Susskind sea quarks. We calculate the scattering lengths of isospin-3/2 D{pi}, D{sub s}{pi}, D{sub s}K, isospin-0 D{anti K} and isospin-1 D{anti K} channels on the lattice. For the chiral extrapolation, we use the chiral unitary approach to next-to-leading order, which at the same time allows us to give predictions for other channels. Furthermore, the hadronic molecular interpretation of the D{sub s0}*(2317) is consistent with our results. The isospin breaking decay width {Gamma}(D{sub s0}*(2317){yields}D{sub s}{pi}) in the hadronic molecular picture is updated to be (89{+-}22)keV.

title: Quenched charmed meson spectra using tadpole improved quark action on anisotropic lattices
abstract: Charmed meson charmonium spectra are studied with improved quark actions on anisotropic lattices. We measured the pseudo-scalar and vector meson dispersion relations for four lowest lattice momentum modes with quark mass values ranging from the strange quark to charm quark with three different values of gauge coupling β and four different values of bare speed of light ν. With the bare speed of light parameter ν tuned in a mass-dependent way, we study the mass spectra of D, Ds, ηc, D*, Ds* and J/ψ mesons. The results extrapolated to the continuum limit are compared with the experiment, and a qualitative agreement is found.

title: Charmed Hadron Interactions
abstract: We compute the scattering lengths of charmed mesons and charmonia scattering with light hadrons in full QCD. We use Fermilab formulation for the charm quark and domain-wall fermions for the light quarks and staggered sea quarks. Four different light-quark masses are used to extrapolate to the physical point. The charmed baryon spectrum is also presented.

title: Tetraquarks, hadronic molecules, meson-meson scattering and disconnected contributions in lattice QCD
abstract: There are generally two types of Wick contractions in lattice QCD calculations of a correlation function: connected and disconnected ones. The disconnected contribution is difficult to calculate and noisy, thus it is often neglected. In the context of studying tetraquarks, hadronic molecules, and mesonmeson scattering, we show that whenever there are both connected and singly disconnected contractions, the singly disconnected part gives the leading order contribution, and thus should never be neglected. As an explicit example, we show that information about the scalar mesons sigma, f(0)(980), a(0)(980), and kappa will be lost when neglecting the disconnected contributions.

title: Singly and Doubly Charmed $J=1/2$ Baryon Spectrum from Lattice QCD
abstract: We compute the masses of the singly and doubly charmed baryons in full QCD using the relativistic Fermilab action for the charm quark. For the light quarks we use domain-wall fermions in the valence sector and improved Kogut-Susskind sea quarks. We use the low-lying charmonium spectrum to tune our heavy-quark action and as a guide to understanding the discretization errors associated with the heavy quark. Our results are in good agreement with experiment within our systematics. For the {Xi}{sub cc}, we find the isospin-averaged mass to be M{sub {Xi}{sub c{sub c}}}=3665{+-}17{+-}14{sub -78}{sup +0} MeV; the three given uncertainties are statistical, systematic, and an estimate of lattice discretization errors, respectively. In addition, we predict the mass splitting of the (isospin-averaged) spin-1/2 {Omega}{sub cc} with the {Xi}{sub cc} to be M{sub {Omega}{sub c{sub c}}}-M{sub {Xi}{sub c{sub c}}}=98{+-}9{+-}22{+-}13 MeV (in this mass splitting, the leading discretization errors are also suppressed by SU(3) symmetry). Combining this splitting with our determination of M{sub {Xi}{sub c{sub c}}} leads to our prediction of the spin-1/2 {Omega}{sub cc} mass, M{sub {Omega}{sub c{sub c}}}=3763{+-}19{+-}26{sub -79}{sup  MeV.

title: Moduli stabilisation in early superstring cosmology
abstract: We study the cosmological evolution induced by the free energy of a string gas at finite temperature. We first consider the maximally supersymmetric heterotic string in the weak coupling regime in dimension D ≥ 4. The free energy develops local minima associated to some gauge symmetry enhancement induced by perturbative states. This can stabilize all heterotic moduli except the dilaton. By string-string S-dualities, it follows that the dual type I moduli can be stabilized by either non perturbative D-string states or perturbative open string states. We next consider the type II string compactified on Calabi-Yau three-folds, which has = 2 supersymmetry in D = 4. The moduli space has singular loci where the Calabi-Yau space undergoes extremal transitions, accompanied with either conifold transitions or certain gauge symmetry enhancement. Also the free energy reaches local minima due to the emergence of extra non perturbative massless modes. Consequently, the type II moduli are attracted to these singular loci. Using the type II/heterotic string duality, we can stabilize the dual heterotic moduli, and in particular it is possible to stabilize the heterotic dilaton.

title: The quantized Schwarzschild Black Hole and the possible origin of Dark Matter

title: The quantum cosmology in the Brans-Dicke theory
abstract: In this paper, we try to establish the quantum cosmology based on the Brans-Dicke gravitational theory. The most remarkable property of it is that the scale factora(t) has a lower limit, where the cosmological wave function approaches zero.

title: Topological limit of gravity admitting an SU(2) connection formulation
abstract: We study the Hamiltonian formulation of the generally covariant theory defined by the Lagrangian 4-form L=e{sub I} and e{sub J} and F{sup IJ}({omega}), where e{sup I} is a tetrad field and F{sup IJ} is the curvature of a Lorentz connection . This theory can be thought of as the limit of the Holst action for gravity for the Newton constant G{yields}{infinity} and Immirzi parameter {gamma}{yields}0, while keeping the product G{gamma} fixed. This theory has for a long time been conjectured to be topological. We prove this statement both in the covariant phase space formulation as well as in the standard Dirac formulation. In the time gauge, the unconstrained phase space of theory admits an SU(2) connection formulation which makes it isomorphic to the unconstrained phase space of gravity in terms of Ashtekar-Barbero variables. Among possible physical applications, we argue that the quantization of this topological theory might shed new light on the nature of the degrees of freedom that are responsible for black entropy in loop quantum gravity.

title: Massless D-strings and moduli stabilization in type I cosmology
abstract: We consider the cosmological evolution induced by the free energy F of a gas of maximally supersymmetric heterotic strings at finite temperature and weak coupling in dimension D ≥ 4. We show that F, which plays the role of an effective potential, has minima associated to enhanced gauge symmetries, where all internal moduli can be attracted and dynamically stabilized. Using the fact that the heterotic/type I S-duality remains valid at finite temperature and can be applied at each instant of a quasi-static evolution, we find in the dual type I cosmology that all internal NS-NS and RR moduli in the closed string sector and the Wilson lines in the open string sector can be stabilized. For the special case of D = 6, the internal volume modulus remains a flat direction, while the dilaton is stabilized. An essential role is played by light D-string modes wrapping the internal manifold and whose contribution to the free energy cannot be omitted, even when the type I string is at weak coupling. As a result, the order of magnitude of the internal radii expectation values on the type I side is $ \sqrt {{{\lambda_{\text{I}}}{\alpha^{\prime}}}} $, where λI is the ten-dimensional string coupling. The non-perturbative corrections to the type I free energy can alternatively be described as effects of “thermal E1-instantons”, whose worldsheets wrap the compact Euclidean time cycle.