Continuum limit of proton decay matrix elements in quenched lattice QCD

We present a lattice QCD calculation of the parameters \alpha and \beta which are necessary in the theoretical estimation of the proton lifetime in grand unified theories (GUTs) using chiral lagrangian approach. The simulation is carried out using the Wilson quark action at three gauge coupling constants in the quenched approximation. We obtain |\alpha(2GeV)|=0.0091(08)(^{+10}_{-19})GeV^3 and |\beta(2GeV)|=0.0098(08)(^{+10}_{-20})GeV^3 in the continuum limit where the first error is statistical and the second one is due to scale setting.Comment: 3 pages, 2 figures, talk presented at Lattice2003(matrix

Inflation and Gauge Hierarchy in Randall-Sundrum Compactification

We obtain the general inflationary solutions for the slab of five-dimensional AdS spacetime where the fifth dimension is an orbifold $S^1/Z_2$ and two three-branes reside at its boundaries, of which the Randall-Sundrum model corresponds to the static limit. The investigation of the general solutions and their static limit reveals that the RS model recasts both the cosmological constant problem and the gauge hierarchy problem into the balancing problem of the bulk and the brane cosmological constants.Comment: 9 pages, revtex, minor changes and more references adde

Lattice QCD calculation of the proton decay matrix element in the continuum limit

We present a quenched lattice QCD calculation of the \alpha and \beta parameters of the proton decay matrix element. The simulation is carried out using the Wilson quark action at three values of the lattice spacing in the range a\approx 0.1-0.064 fm to study the scaling violation effect. We find only mild scaling violation when the lattice scale is determined by the nucleon mass. We obtain in the continuum limit, |\alpha(NDR,2GeV)|=0.0090(09)(^{+5}_{-19})GeV^3 and |\beta(NDR,2GeV)|=0.0096(09)(^{+6}_{-20})GeV^3 with \alpha and \beta in a relatively opposite sign, where the first error is statistical and the second is due to the uncertainty in the determination of the physical scale.Comment: 4 pages, 3 figure

Effective Gauss-Bonnet Interaction in Randall-Sundrum Compactification

The effective gravitational interaction below the Planck scale in the Randall-Sundrum world is shown to be the Gauss-Bonnet term. In this theory we find that there exists another static solution with a positive bulk cosmological constant. Also, there exist solutions for positive visible sector cosmological constant, which are needed for a later Friedman-Robertson-Walker universe.Comment: 10 pages, including 1 eps figur

Non-minimal Split Supersymmetry

We present an extension of the minimal split supersymmetry model, which is capable of explaining the baryon asymmetry of the Universe. Instead of MSSM we start from NMSSM and split its spectrum in such a way that the low energy theory contains neutral particles, in addition to the content of minimal split supersymmetry. They trigger the strongly first order electroweak phase transition (EWPT) and provide an additional source of CP-violation. In this model, we estimate the amount of the baryon asymmetry produced during EWPT, using WKB approximation for CP-violating sources in diffusion equations. We also examine the contribution of CP-violating interactions to the electron and neutron electric dipole moments and estimate the production of the neutralino dark matter. We find that both phenomenological and cosmological requirements can be fulfilled in this model.Comment: 31 pages, 9 figures, typos correcte

Cyanide-Bridged Decanuclear Cobalt–Iron Cage

A cyanide-bridged decanuclear [Co6Fe4] cluster was synthesized by a one-pot reaction, and the magnetic properties and electronic configuration were investigated. The complex displayed thermally controlled electron-transfer-coupled spin transition (ETCST) behavior between CoIII low-spin–NC–FeII low-spin and CoII high-spin–NC–FeIII low-spin states, as confirmed by single-crystal X-ray, magnetic, and Mössbauer analyses

Spectrum from the warped compactifications with the de Sitter universe

We discuss the spectrum of the tensor metric perturbations and the stability of warped compactifications with the de Sitter spacetime in the higher-dimensional gravity. The spacetime structure is given in terms of the warped product of the non-compact direction, the spherical internal dimensions and the four-dimensional de Sitter spacetime. To realize a finite bulk volume, we construct the brane world model, using the cut-copy-paste method. Then, we compactify the spherical directions on the brane. In any case, we show the existence of the massless zero mode and the mass gap of it with massive Kaluza-Klein modes. Although the brane involves the spherical dimensions, no light massive mode is excited. We also investigate the scalar perturbations, and show that the model is unstable due to the existence of a tachyonic bound state, which seems to have the universal negative mass square, irrespective of the number of spacetime dimensions.Comment: Journal version (JHEP

Scalar Hair of Global Defect and Black Brane World

We consider a complex scalar field in (p+3)-dimensional bulk with a negative cosmological constant and study global vortices in two extra-dimensions. We reexamine carefully the coupled scalar and Einstein equations, and show that the boundary value of scalar amplitude at infinity of the extra-dimensions should be smaller than vacuum expectation value. The brane world has a cigar-like geometry with an exponentially decaying warp factor and a flat thick p-brane is embedded. Since a coordinate transformation identifies the obtained brane world as a black p-brane world bounded by a horizon, this strange boundary condition of the scalar amplitude is understood as existence of a short scalar hair.Comment: 26 pages, 2 figure

Cosmological Challenges in Theories with Extra Dimensions and Remarks on the Horizon Problem

We consider the cosmology that results if our observable universe is a 3-brane in a higher dimensional universe. In particular, we focus on the case where our 3-brane is located at the $Z_2$ symmetry fixed plane of a $Z_2$ symmetric five-dimensional spacetime, as in the Ho\v{r}ava-Witten model compactified on a Calabi-Yau manifold. As our first result, we find that there can be substantial modifications to the standard Friedmann-Robertson-Walker (FRW) cosmology; as a consequence, a large class of such models is observationally inconsistent. In particular, any relationship between the Hubble constant and the energy density on our brane is possible, including (but not only) FRW. Generically, due to the existence of the bulk and the boundary conditions on the orbifold fixed plane, the relationship is not FRW, and hence cosmological constraints coming from big bang nucleosynthesis, structure formation, and the age of the universe difficult to satisfy. We do wish to point out, however, that some specific choices for the bulk stress-energy tensor components do reproduce normal FRW cosmology on our brane, and we have constructed an explicit example. As our second result, for a broad class of models, we find a somewhat surprising fact: the stabilization of the radius of the extra dimension and hence the four dimensional Planck mass requires unrealistic fine-tuning of the equation of state on our 3-brane. In the last third of the paper, we make remarks about causality and the horizon problem that apply to {\it any} theory in which the volume of the extra dimension determines the four-dimensional gravitational coupling. We point out that some of the assumptions that lead to the usual inflationary requirements are modified.Comment: 15 page REVTeX file; to appear in Phys. Rev. D; clarified the statement of being able to obtain any power dependence of the Hubble expansion rate on the energy density; added reference