Unstable Dp-brane Research Articles

Note about D-branes in Carrollian background

This paper is devoted to the construction of stable and unstable Dp-branes in generalized Carroll space-times. We also study tachyon solutions on the world-volume of unstable Dp-brane in Carrollian background and discuss their physical interpretations.

Gravitational and dilatonic radiations from the parallel dressed-dynamical unstable D[formula omitted]-branes

In the context of the bosonic string theory, we shall extract the general radiation amplitude of a massless closed string from the interaction of two parallel unstable Dp-branes. The branes are non-stationary and have been dressed by background fields. The foregoing amplitude will be rewritten for the massless state radiation from the branes with the large distance. Besides, we shall study the gravitational and dilatonic radiations from this configuration.

Radiation of closed strings between the parallel dynamical-dressed unstable Dp-branes

We introduce a boundary state which is corresponding to a Dp-brane with tangential dynamics in the presence of the Kalb-Ramond field, a tachyonic field and a U(1) gauge potential in a special gauge. From the interaction of such branes radiation amplitude of a general massless closed string will be computed. The effects of the large distances of the branes on this radiation will be studied. In the large distances of the branes, the possibility of axion radiation will be investigated. Our calculations will be in the context of the bosonic string theory.

Stable and unstable Dp-branes in p-brane Newton–Cartan background

We formulate Dp-brane Newton–Cartan (NC) background through the limiting procedure from relativistic Dirac–Born–Infeld action and Wess–Zumino term. We also determine action for unstable D(p + 1)-brane in Dp-brane NC background and study its properties.

Note about covariant Hamiltonian formalism for strings, p-branes and unstable Dp-branes

In this short note we formulate Covariant Hamiltonian formalism for strings, p-branes and Non-BPS Dp-branes. We also analyse the vacuum tachyon condensation in case of unstable D1-brane.

Unstable D-brane in torsional Newton-Cartan background

This paper is devoted to the construction of unstable D-brane action in torsional Newton-Cartan background through T-duality along null direction. We determine corresponding equations of motion and analyze their solution that corresponds to lower dimensional non-relativistic D(p-1)-brane. We also find Hamiltonian for unstable Dp-brane and study tachyon vacuum solutions that can be interpreted as gas of non-relativistic strings.

Carroll limit of non-BPS Dp-brane

We find Carroll non-BPS Dp-brane action by performing Carroll limit of a canonical form of unstable Dp-brane action. We analyze different Carroll limits and discuss solutions of the equations of motion of Carroll non-BPS Dp-brane at the tachyon vacuum.

Note about unstable D-branes with dynamical tension

We propose an action for unstable Dp-brane with dynamical tension. We show that the equations of motion are equivalent to the equations of motion derived from DBI and WZ actions for non-BPS Dp-brane. We also find Hamiltonian formulation of this action and analyze properties of the solutions corresponding to the tachyon vacuum and zero tension solution.

Newp+1dimensional nonrelativistic theories from Euclidean stable and unstable Dp-branes

In this paper we continue the study of non-relativistic p+1 dimensional theories that we started at arXiv:0904.1343. We extend the analysis presented there to the case of stable and unstable Dp-branes.

Exact BPS Kink in BCFT, DBI EFT, NCFT, and BSFT

We discuss single topological BPS kinks with non-zero thickness, which are exact solutions in various contexts including Dirac-Born-Infeld type effective field theory, noncommutative field theory, boundary conformal field theory, and boundary string field theory. The tachyon field is monotonically increasing (or decreasing) and connects the isolated vacua at positive and negative infinity irrespective of the theories of our interest. It is expressed by a simple linear function, τ (X) ∝ X, in the case of boundary conformal field theory. The obtained tachyon kink in the presence of critical electromagnetic field is interpreted as a single thick BPS D(p− 1)-brane (or D(p− 1)F1-composite) inside an unstable Dp-brane with background fluid of fundamental strings.

Noncommutative Tachyon Kinks as D(p-1)-branes from Unstable Dp-brane

We study noncommutative (NC) field theory of a real NC tachyon and NC U(1) gauge field, describing the dynamics of an unstable D$p$-brane. For every given set of diagonal component of open string metric $G_{0}$, NC parameter $\theta_{0}$, and interpolating electric field ${\hat E}$, we find all possible static NC kinks as exact solutions, in spite of complicated NC terms, which are classified by an array of NC kink-antikink and topological NC kinks. By computing their tensions and charges, those configurations are identified as an array of D0${\bar {\rm D}}$0 and single stable D0 from the unstable D1, respectively. When the interpolating electric field has critical value as $G_{0}^{2}={\hat E}^{2}$, the obtained topological kink becomes a BPS object with nonzero thickness and is identified as BPS D0 in the fluid of fundamental strings. Particularly in the scaling limit of infinite $\theta_{0}$ and vanishing $G_{0}$ and ${\hat E}$, while keeping $G_{0}\theta_{0}={\hat E}\theta_{0}=1$, finiteness of the tension of NC kink corresponds to tensionless kink in ordinary effective field theory. An extension to stable D$(p-1)$ from unstable D$p$ is straightforward for pure electric cases with parallel NC parameter and interpolating two-form field.

Inhomogeneous fragmentation of the rolling tachyon

Dirac-Born-Infeld type effective actions reproduce many aspects of string theory classical tachyon dynamics of unstable Dp-branes. The inhomogeneous tachyon field rolling from the top of its potential forms topological defects of lower codimensions. In between them, as we show, the tachyon energy density fragments into a p-dimensional web-like high density network evolving with time. We present an analytic asymptotic series solution of the non-linear equations for the inhomogeneous tachyon and its stress energy. The generic solution for a tachyon field with a runaway potential in arbitrary dimensions is described by the free streaming of noninteracting massive particles whose initial velocities are defined by the gradients of the initial tachyon profile. Thus, relativistic particle mechanics is a dual picture of the tachyon field effective action. Implications of this picture for inflationary models with a decaying tachyon field are discussed.

A note on the singularity theorem for supergravity SD-branes

Recently, a singularity theorem for full SD-brane spacetimes was given in hep-th/0305055. We comment on the relation between this and previous work as well as provide a more geometric formulation interpreted as a no-go theorem. We then point out that some setups of physical interest escape the theorem: cosmological applications, half-SDp-branes and decaying unstable Dp-branes for general p. We also provide indications that the space-filling full SD8-brane (in d=10) escapes as well, because of the important role of Ramond-Ramond fields. In any case, tachyon cosmology is not ruled out by the no-go theorem. Lastly, we remark upon interesting directions for potential generalizations of the theorem, and quantum corrections.

Tachyon kinks on unstable Dp-branes

In the context of tachyon effective theory coupled to Born-Infeld electromagnetic fields, we obtain all possible singularity-free static flat configurations of codimension one on unstable Dp-branes. Computed tension and string charge density suggest that the obtained kinks are D(p-1) or D(p-1)F1-branes.

String fluid, tachyon matter, and domain walls

We study classical dynamics of an open string tachyon $T$ of unstable D$p$-brane coupled to the gauge field $A_\mu$. In the vacuum with vanishing potential, V=0, two fluid-like degrees of freedom, string fluid and tachyon matter, survive the tachyon condensation. We offer general analysis of the associated Hamiltonian dynamics in arbitrary background. The canonical field equations are organized into two sets, fluid equations of motion augmented by an integrability condition. We show that a large class of motionless and degenerate family of classical solutions exist and represent arbitrary transverse distribution of tachyon matter and flux lines. We further test their stability by perturbing the fluid equation up to the second order. Second half of this note considers possibility of $V \neq 0$ in the dynamics. We incorporate $V$ in the Hamiltonian equation of motion and consider interaction between domain walls and string fluid. During initial phase of tachyon condensation, topological defect at T=0 is shown to attract nearby and parallel flux lines. The final state is fundamental strings absorbed and spread in some singular D$(p-1)$ brane soliton. When string fluid is transverse to the domain wall, the latter is known to turn into a smooth solution. We point out that a minimal solution of this sort exists and saturates a BPS energy bound of fundamental string ending on a D$(p-1)$ brane.

D-branes and KK-theory in Type I String Theory

We analyse unstable D-brane systems in type I string theory. Generalizing the proposal in hep-th/0108085, we give a physical interpretation for real KK-theory and claim that the D-branes embedded in a product space X x Y which are made from the unstable Dp-brane system wrapped on Y are classified by a real KK-theory group KKO^{p-1}(X,Y). The field contents of the unstable D-brane systems are systematically described by a hidden Clifford algebra structure. We also investigate the matrix theory based on non-BPS D-instantons and show that the spectrum of D-branes in the theory is exactly what we expect in type I string theory, including stable non-BPS D-branes with Z_2 charge. We explicitly construct the D-brane solutions in the framework of BSFT and analyse the physical property making use of the Clifford algebra.

Noncommutative tachyons

When unstable Dp-branes in type II string theory are placed in a B-field, the resulting tachyonic world-volume theory becomes noncommutative. We argue that for large noncommutativity parameter, condensation of the tachyon as a noncommutative soliton leads to new decay modes of the Dp-brane into (p-2)-brane configurations, which we interpret as suitably smeared BPS D(p-1)-branes. Some of these configurations are metastable. We discuss various generalizations of this decay process.