14437282
Domain walls in noncommutative field theories
We study kinks in a wide class of noncommutative (NC) field theories. We find rich structure of the static kinks in DBI type NC tachyon action for an unstable Dp-brane with general constant open string metric and NC parameter. Among which thick topological BPS NC kink and tensionless half-kink are particularly intriguing. Reproduction of the correct decent relation between Dp and D(p−1) lets us interpret the obtained NC kinks as codimension-one D-brane and its composites. If we turn on DBI type NC U(1) gauge field on an unstable D2-brane, only constant field strength is allowed by gauge equation and NC Bianchi identity. Inclusion of the NC U(1) gauge field induces fundamental string charge localized on the codimension-one brane, which turns D(p−1) into D(p−1)F1.
2435715
Late time behaviors of an inhomogeneous rolling tachyon
We study an inhomogeneous decay of an unstable D-brane in the context of Dirac-Born-Infeld (DBI)-type effective action. We consider tachyon and electromagnetic fields with dependence of time and one spatial coordinate, and an exact solution is found under an exponentially decreasing tachyon potential, e{sup -|T|/{radical}}{sup (2)}, which is valid for the description of the late time behavior of an unstable D-brane. Though the obtained solution contains both time and spatial dependence, the corresponding momentum density vanishes over the entire spacetime region. The solution is governed by two parameters. One adjusts the distribution of energy density in the inhomogeneous direction, and the other interpolates between the homogeneous rolling tachyon and static configuration. As time evolves, the energy of the unstable D-brane is converted into the electric flux and tachyon matter.
14606908
Evolution of tachyon kink with electric field
We investigate the decay of an inhomogeneous D1-brane wrapped on a S1 with an electric field. The model that we consider consists of an array of tachyon kink and anti-kink with a constant electric flux. Beginning with an initially static configuration, we numerically evolve the tachyon field with some perturbations under a fixed boundary condition at diametrically opposite points on the circle S1. When the electric flux is smaller than the critical value, the tachyon kink becomes unstable; the tachyon field rolls down the potential, and the lower dimensional D0- and 0-brane become thin, which resembles the caustic formation known for this type of the system in the literature. For the supercritical values of the electric flux, the tachyon kink remains stable.
119244769
Solutions in IR Modified Horava-Lifshitz Gravity
In order to allow the asymptotically flat, we consider Ho\v{r}ava-Lifshitz gravity theory with a soft violation of the detailed balance condition and obtain various solutions. In particular, we find that such theory coupled to a global monopole leads to a solution representing a space with deficit solid angle, which is well matched with genuine feature of GR.
17425045
Tachyon Kinks
We study Born-Infeld type tachyonic effective action of unstable D2-brane with a runaway potential and find rich structure of static regular solitonic solutions. There exists only periodic array of tachyon kink-antikinks in pure tachyonic theory, however, in the presence of electromagnetic fields, solutions include periodic arrays, topological tachyon kinks, half kink, and bounces. Computed tension of each kink or single unit of the periodic array has T 1 = √ 2πT 2 or that with a multiplicative factor depending on electric field. When both electric and magnetic fields are turned on, fundamental string charge density has a confined component in addition to a constant piece. These evidences imply that the obtained codimension-1 objects are likely to be interpreted as D1-brane (and D1F1) or array of D1 ¯ D1 (and D1F1-¯ D1F1) as was the case without the electromagnetic fields. Generalization to unstable Dp-branes is straightforward.
118173758
Unstable D-branes and String Cosmology
Cosmological implication of rolling tachyons is reported in the context of effective field theory. With a brief review of rolling tachyons in both flat and curved spacetimes, we study the string cosmological model with both tachyon and dilaton. In the string frame, flat space solutions of both initial-stage and late-time are obtained in closed form. In the Einstein frame, every expanding solution is decelerating. When a Born-Infeld U(1) gauge field is coupled, enhancement of e-folding of scale factor is also discussed by numerical analysis.
34982894
Flavored quantum Boltzmann equations
We derive from first principles, using nonequilibrium field theory, the quantum Boltzmann equations that describe the dynamics of flavor oscillations, collisions, and a time-dependent mass matrix in the early universe. Working to leading nontrivial order in ratios of relevant time scales, we study in detail a toy model for weak-scale baryogenesis: two scalar species that mix through a slowly varying time-dependent and CP-violating mass matrix, and interact with a thermal bath. This model clearly illustrates how the CP asymmetry arises through coherent flavor oscillations in a nontrivial background. We solve the Boltzmann equations numerically for the density matrices, investigating the impact of collisions in various regimes.
119229852
Factorization of e+e- event shape distributions with hadronic final states in soft collinear effective theory
We present a new analysis of two-jet event shape distributions in soft collinear effective theory. Extending previous results, we observe that a large class of such distributions can be expressed in terms of vacuum matrix elements of operators in the effective theory. We match these matrix elements to the full theory in the two-jet limit without assuming factorization of the complete set of hadronic final states into independent sums over partonic collinear and soft states. We also briefly discuss the relationship of this approach to diagrammatic factorization in the full theory.
120085942
Nucleation of vacuum bubbles of a self-gravitating scalar field
The case of a self-gravitating scalar field under-going the first-order phase transition is studied. Particularly the effects of self gravity on the nucleation of vacuum bubbles is investigated. We also investigate what modifications are induced by the introduction of nonminimal coupling of the scalar field. The possibility of nucleation of false vacuum bubbles within the true vacuum background in the case of a nonminimally coupled scalar field is discussed.
119269079
Double non-global logarithms in-n-out of jets
A bstractWe derive the leading non-global logarithms (NGLs) of ratios of jet masses m1,2 and a jet energy veto Λ due to soft gluons splitting into regions in and out of jets. Such NGLs appear in any exclusive jet cross section with multiple jet measurements or with a veto imposed on additional jets. Here, we consider back-to-back jets of radius R produced in e+e− collisions, found with a cone or recombination algorithm. The leading NGLs are of the form $\alpha_{\text{s}}^2{\text{l}}{{\text{n}}^2}(\Lambda /{m_{{1},{2}}})$ or $\alpha_{\text{s}}^2{\text{l}}{{\text{n}}^2}({m_1}/{m_2})$. Their coefficients depend both on the algorithm and on R. We consider cone, kT, anti-kT, and Cambridge-Aachen algorithms. In addition to determining the full algorithmic and R dependence of the leading NGLs, we derive new relations among their coefficients. We also derive to all orders in αs a factorized form for the soft function S(kL, kR, Λ) in the cross section σ(m1, m2, Λ) in which dependence on each of the global logs of μ/kL, μ/kR and μ/Λ determined by the renormalization group are separated from one another and from the non-global logs. The same kind of soft function, its associated non-global structure, and the algorithmic dependence we derive here will also arise in exclusive jet cross sections at hadron colliders, and must be understood and brought under control to achieve precise theoretical predictions.
1357101
Pulsar magnetospheres: a general relativistic treatment
A fully general relativistic description of pulsar magnetospheres is provided. To be more specific, a study of pulsar magnetospheres is performed in the context of general relativistic magnetohydrodynamics (MHD) employing the so-called Grad–Shafranov approach. Not surprisingly, the resulting Grad–Shafranov equations and all the other related general relativistic MHD equations turn out to take essentially the same structures as those for a (rotating) black hole magnetosphere. Other different natures between the two cases including the structure of singular surfaces of MHD flows in each magnetosphere are essentially encoded in the different space–time (metric) contents. In this way, pulsar and black hole magnetospheres can be described in a unified fashion. Particularly, the direction of poloidal currents circulating in the neutron star magnetosphere turns out to be the same as that of currents circulating in a black hole magnetosphere, which in turn leads to pulsar and black hole spin-down via ‘magnetic braking’.