Instanton-inspired model of QCD phase transitions and bubble dynamics
We have reinvestigated the collision of gluonic bubbles in an SU(2) model of QCD which was studied by Johnson, Choi, and Kisslinger in the context of the instanton-inspired model of QCD phase transition bubbles with plane-wave approximation. We discuss treacherous points of the instanton-inspired model that cause the violation of causality due to the presence of imaginary gluon fields. By constructing a new slightly modified Lorentzian model where we have three independent real gluon fields, we reanalyzed the process of bubble collisions. Our numerical results show some indication of forming a bubble wall in the colliding region.

title: ON WILSON SURFACES IN TOPOLOGICAL CHERN-SIMONS INTERACTION IN 3+1 DIMENSIONS
abstract: We comment on the regularization of the expectation values of Wilson surfaces for the bosonic string in 3+1 dimensions. We analyze the singular behaviors of propagators for the Chern-Simons action with the additional higher order terms.

title: Global and local D-vortices
abstract: Codimension-two objects on a system of brane-antibrane are studied in the context of Born-Infeld type effective field theory with a complex tachyon and U(1) × U(1) gauge fields. When the radial electric field is turned on in D2 ¯ D2, we find static regular global and local D-vortex solutions which could be candidates of straight cosmic D-strings in a superstring theory. A natural extension to DF-strings is briefly discussed.

title: Extraordinary vacuum black string solutions
abstract: In addition to the boosted static solution there are two other classes of stationary stringlike solutions of the vacuum Einstein equation in (4+1) dimensions. Each class is characterized by three parameters of mass, tension, and momentum flow along the fifth coordinate. We analyze the metric properties of one of the two classes, which was previously assumed to be naked singular, and show that the solution spectrum contains black string and wormhole in addition to the known naked singularity as the momentum flow to mass ratio increases. Interestingly, there does not exist new zero momentum solution in these cases.

title: An efficient representation of Euclidean gravity I
abstract: A bstractWe explore how the topology of spacetime fabric is encoded into the local structure of Riemannian metrics using the gauge theory formulation of Euclidean gravity. In part I, we provide a rigorous mathematical foundation to prove that a general Einstein manifold arises as the sum of SU(2)L Yang-Mills instantons and SU(2)R anti-instantons where SU(2)L and SU(2)R are normal subgroups of the four-dimensional Lorentz group Spin(4) = SU(2)L × SU(2)R. Our proof relies only on the general properties in four dimensions: The Lorentz group Spin(4) is isomorphic to SU(2)L × SU(2)R and the six-dimensional vector space Λ2T∗M of two-forms splits canonically into the sum of three-dimensional vector spaces of self-dual and anti-self-dual two-forms, i.e., $ {\Lambda^2}{T^{ * }}M = \Lambda_{ + }^2 \oplus \Lambda_{ - }^2 $. Consolidating these two, it turns out that the splitting of Spin(4) is deeply correlated with the decomposition of two-forms on four-manifold which occupies a central position in the theory of four-manifolds.

title: Classical stability of black D3-branes
abstract: We have investigated the classical stability of charged black D3-branes in the type-IIB supergravity under small perturbations. For s-wave perturbations it turns out that black D3-branes are unstable when they have small charge density. As the charge density increases for given mass density, however, the instability decreases down to zero at a certain finite value of the charge density, and then black D3-branes become stable all the way down to the extremal point. It has also been shown that such critical value at which its stability behavior changes agrees very well with the predicted one by the thermodynamic stability behavior of the corresponding black hole system through the Gubser-Mitra conjecture. Unstable mode solutions we found involve non-vanishing fluctuations of the self-dual five-form field strength. Some implications of our results are also discussed.

title: Gaugino masses from gravitino at one loop
abstract: The N=1 supergravity coupled to chiral and Yang-Mills superfields is regarded as the ultraviolet theory of the supersymmetric Standard Model. The gravitino acquires a mass from the hidden sector and participate in mediating supersymmetry breaking to the visible sector. We consider the quantum effects of the gravitino and evaluate its contribution to the gaugino masses at one loop level, which turns out to be irrespective of the SM gauge couplings. Due to the universality of gravitino, its contribution to the gaugino masses can significantly modify the gaugino mass relations of other supersymmetry breaking mechanisms depending on the gravitino mass. For a given gaugino mass the gravitino mass cannot be arbitrarily large even when other supersymmetry breaking mechanisms are dominant.

title: Bremsstrahlung radiation at a vacuum bubble wall
abstract: When charged particles collide with a vacuum bubble, they can radiate strong electromagnetic waves due to rapid deceleration. Owing to the energy loss of the particles by this bremsstrahlung radiation, there is a non-negligible damping pressure acting on the bubble wall even when thermal equilibrium is maintained. In the non-relativistic region, this pressure is proportional to the velocity of the wall and could have influenced the bubble dynamics in the early universe.

title: Radiation Damping at a Bubble Wall
abstract: The first order phase transition proceeds via nucleation and growth of true vacuum bubbles. When charged particles collide with the bubble they could radiate electromagnetic wave. We show that, due to an energy loss of the particles by the radiation, the damping pressure acting on the bubble wall depends on the velocity of the wall even in a thermal equilibrium state.

title: Optimal spin-quantization axes for the polarization of dileptons with large transverse momentum
abstract: The leading-order parton processes that produce a dilepton with large transverse momentum predict that the transverse polarization should increase with the transverse momentum for almost any choice of the quantization axis for the spin of the virtual photon. The rate of approach to complete transverse polarization depends on the choice of spin quantization axis. We propose axes that optimize that rate of approach. They are determined by the momentum of the dilepton and the direction of the jet that provides most of the balancing transverse momentum.

title: Variations in the Na—O anticorrelation in globular clusters: evidence for a deep mixing episode in red giant branch stars
abstract: The Na–O anticorrelation seen in almost all globular clusters ever studied using high-resolution spectroscopy is now generally explained by the primordial pollution from the first generation of the intermediate-mass asymptotic giant branch stars to the protostellar clouds of the second generation of stars. However, the primordial pollution scenario may not tell the whole story for the observed Na–O anticorrelations in globular clusters. Using the recent data by Carretta and his collaborators, the different shapes of the Na–O anticorrelations for red giant branch stars brighter than and fainter than the red giant branch bump can be clearly seen. If the elemental abundance measurements by Carretta and his collaborators are not greatly in error, this variation in the Na–O anticorrelation against luminosity indicates an internal deep mixing episode during the ascent of the low-mass red giant branch in globular clusters. Our result implies that the multiple stellar population division scheme solely based on [O/Fe] and [Na/Fe] ratios of a globular cluster, which is becoming popular, is not reliable for stars brighter than the red giant branch bump. Our result also suggests that sodium supplied by the deep mixing may alleviate the sodium underproduction problem within the primordial asymptotic giant branch pollution scenario.