333 research outputs found
Towards the Formal Specification and Verification of Maple Programs
In this paper, we present our ongoing work and initial results on the formal
specification and verification of MiniMaple (a substantial subset of Maple with
slight extensions) programs. The main goal of our work is to find behavioral
errors in such programs w.r.t. their specifications by static analysis. This
task is more complex for widely used computer algebra languages like Maple as
these are fundamentally different from classical languages: they support
non-standard types of objects such as symbols, unevaluated expressions and
polynomials and require abstract computer algebraic concepts and objects such
as rings and orderings etc. As a starting point we have defined and formalized
a syntax, semantics, type system and specification language for MiniMaple
Long Lived Large Type II Strings: decay within compactification
Motivated also by recent revival of interest about metastable string states
(as cosmic strings or in accelerator physics), we study the decay, in presence
of dimensional compactification, of a particular superstring state, which was
proven to be remarkably long-lived in the flat uncompactified scenario. We
compute the decay rate by an exact numerical evaluation of the imaginary part
of the one-loop propagator. For large radii of compactification, the result
tends to the fully uncompactified one (lifetime T = const M^5/g^2), as
expected, the string mainly decaying by massless radiation. For small radii,
the features of the decay (emitted states, initial mass dependence,....)
change, depending on how the string wraps on the compact dimensions.Comment: 32 pages, 24 text plus appendices, 4 figure
Dyonic p-branes from self-dual (p+1)-branes
The `electromagnetic' Sl(2;\bZ) duality group in spacetime dimension
can be given a Kaluza-Klein interpretation in as the modular group of
a compactifying torus. We show how dyonic -branes in can be
interpreted as self-dual -branes in wound around the homology
cycles of the torus. In particular, dyons of the D=4 N=4 heterotic string
theory are interpreted as winding modes of a D=6 self-dual string, while D=8
dyonic membranes are interpreted as wound 3-branes of D=10 IIB superstring
theory. We also discuss the T-dual IIA interpretations of D=8 dyonic membranes.Comment: 16 pp. phyzzx. 1 fi
Superstrings and D-branes in A Plane Wave
We carefully analyze the supersymmetry algebra of closed strings and open
strings in a type IIB plane wave background. We use eight component chiral
spinors, SO(8) Majorana-Weyl spinors, in light-cone gauge to provide a useful
basis of string field theory calculation in the plane wave. We consider the two
classes of D-branes, -branes, and give a worldsheet derivation of
conserved supercurrents for all half BPS D-branes preserving 16 supersymmetries
in the type IIB plane wave background. We exhaustively provide the
supersymmetry algebra of the half BPS branes as well. We also point out that
the supersymmetry algebra distinguishes the two SO(4) directions with relative
sign which is consistent with the Z_2 symmetry of the string action.Comment: v4: 28 pages, Latex, Worldsheet derivation of conserved supercurrents
for all half BPS D-branes newly added, improved presentation and typo
Super D-branes from BRST Symmetry
Recently a new formalism has been developed for the covariant quantization of
superstrings. We study properties of Dp-branes and p-branes in this new
framework, focusing on two different topics: effective actions and boundary
states for Dp-branes. We present a derivation of the Wess-Zumino terms for
super (D)p-branes using BRST symmetry. To achieve this we derive the BRST
symmetry for superbranes, starting from the approach with/without pure spinors,
and completely characterize the WZ terms as elements of the BRST cohomology. We
also develope the boundary state description of Dp-branes by analyzing the
boundary conditions for open strings in the completely covariant (i.e., without
pure spinors) BRST formulation.Comment: 31 pp; journal version, expended discussion of D-brane pure spinor
constraints in Section 2.
Intersecting D-branes in Type IIB Plane Wave Background
We study intersecting D-branes in a type IIB plane wave background using
Green-Schwarz worldsheet formulation. We consider all possible -branes
intersecting at angles in the plane wave background and identify their residual
supersymmetries. We find, in particular, that brane
intersections preserve no supersymmetry. We also present the explicit
worldsheet expressions of conserved supercharges and their supersymmetry
algebras.Comment: 32 pages, 2 tables; Corrected typos, to appear in Phys. Rev.
D-brane Decay in Two-Dimensional String Theory
We consider unstable D0-branes of two dimensional string theory, described by
the boundary state of Zamolodchikov and Zamolodchikov [hep-th/0101152]
multiplied by the Neumann boundary state for the time coordinate . In the
dual description in terms of the matrix model, this D0-brane is described
by a matrix eigenvalue on top of the upside down harmonic oscillator potential.
As suggested by McGreevy and Verlinde [hep-th/0304224], an eigenvalue rolling
down the potential describes D-brane decay. As the eigenvalue moves down the
potential to the asymptotic region it can be described as a free relativistic
fermion. Bosonizing this fermion we get a description of the state in terms of
a coherent state of the tachyon field in the asymptotic region, up to a
non-local linear field redefinition by an energy-dependent phase. This coherent
state agrees with the exponential of the closed string one-point function on a
disk with Sen's marginal boundary interaction for which describes D0-brane
decay.Comment: 19 pages, harvmac, minor change
- …