5,154 research outputs found
Noncommutativity relations in type IIB theory and their supersymmetry
In the present paper we investigate noncommutativity of and -brane
world-volumes embedded in space-time of type IIB superstring theory. Boundary
conditions, which preserve half of the initial supersymmetry, are treated as
canonical constraints. Solving the constraints we obtain original coordinates
in terms of the effective coordinates and momenta. Presence of momenta induces
noncommutativity of string endpoints. We show that noncommutativity relations
are connected by N=1 supersymmetry transformations and noncommutativity
parameters are components of N=1 supermultiplet
Drug Release from Viscoelastic Swelling Polymeric Platforms
We consider a polymeric spherical platform containing a solid dispersed drug that is
in contact with a solvent fluid. While swelling, a non-Fickian sorption of the solvent molecules occurs
induced by the effect of the viscoelastic properties of the polymer. The solid drug in contact with
the solvent fluid dissolves and a Fickian release of dissolved drug takes place. The fluid entrance, the
drug dissolution, and the drug release to an external environment are described by a system of PDEs
complemented with an equation for the swelling front, initial, and boundary conditions. The model
includes the two major factors that govern a swelling process of a polymeric platform within a release
medium: the cross-link density and the concentration of the external medium. Energy estimates
for the mass of solvent fluid and of undissolved and dissolved drug in the polymeric platform are
established. Numerical simulations that illustrate the theoretical results are also included
On maximally supersymmetric Yang-Mills theories
We consider ten-dimensional supersymmetric Yang-Mills theory (10D SUSY YM
theory) and its dimensional reductions, in particular, BFSS and IKKT models. We
formulate these theories using algebraic techniques based on application of
differential graded Lie algebras and associative algebras as well as of more
general objects, L_{\infty}- and A_{\infty}- algebras.
We show that using pure spinor formulation of 10D SUSY YM theory equations of
motion and isotwistor formalism one can interpret these equations as
Maurer-Cartan equations for some differential Lie algebra. This statement can
be used to write BV action functional of 10D SUSY YM theory in Chern-Simons
form. The differential Lie algebra we constructed is closely related to
differential associative algebra Omega of (0, k)-forms on some supermanifold;
the Lie algebra is tensor product of Omega and matrix algebra .
We construct several other algebras that are quasiisomorphic to Omega and,
therefore, also can be used to give BV formulation of 10D SUSY YM theory and
its reductions. In particular, Omega is quasiisomorphic to the algebra B
constructed by Berkovits. The algebras Omega_0 and B_0 obtained from Omega and
B by means of reduction to a point can be used to give a BV-formulation of IKKT
model.
We introduce associative algebra SYM as algebra where relations are defined
as equations of motion of IKKT model and show that Koszul dual to the algebra
B_0 is quasiisomorphic to SYM.Comment: 43 pages. Details are added in the construction of trace in section
4. Added references. Formula for vector filed E on p.5,11 correcte
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.
Toric Calabi-Yau Fourfolds, Duality Between N=1 Theories and Divisors that Contribute to the Superpotential
We study issues related to F-theory on Calabi-Yau fourfolds and its duality to heterotic theory for Calabi-Yau threefolds. We discuss principally fourfolds that are described by reflexive polyhedra and show how to read off some of the data for the heterotic theory from the polyhedron. We give a procedure for constructing examples with given gauge groups and describe some of these examples in detail. Interesting features arise when the local pieces are fitted into a global manifold. An important issue is how to compute the superpotential explicitly. Witten has shown that the condition for a divisor to contribute to the superpotential is that it have arithmetic genus 1. Divisors associated with the short roots of non-simply laced gauge groups do not always satisfy this condition while the divisors associated to all other roots do. For such a `dissident' divisor we distinguish cases for which the arithmetic genus is greater than unity corresponding to an X that is not general in moduli (in the toric case this corresponds to the existence of non-toric parameters). In these cases the `dissident' divisor D does not remain an effective divisor for general complex structure. If however the arithmetic genus is less than or equal to 0, then the divisor is general in moduli and there is a genuine instability
F-theory on Genus-One Fibrations
We argue that M-theory compactified on an arbitrary genus-one fibration, that
is, an elliptic fibration which need not have a section, always has an F-theory
limit when the area of the genus-one fiber approaches zero. Such genus-one
fibrations can be easily constructed as toric hypersurfaces, and various
and models are presented as examples. To each
genus-one fibration one can associate a -function on the base as well as
an representation which together define the IIB axio-dilaton
and 7-brane content of the theory. The set of genus-one fibrations with the
same -function and representation, known as the
Tate-Shafarevich group, supplies an important degree of freedom in the
corresponding F-theory model which has not been studied carefully until now.
Six-dimensional anomaly cancellation as well as Witten's zero-mode count on
wrapped branes both imply corrections to the usual F-theory dictionary for some
of these models. In particular, neutral hypermultiplets which are localized at
codimension-two fibers can arise. (All previous known examples of localized
hypermultiplets were charged under the gauge group of the theory.) Finally, in
the absence of a section some novel monodromies of Kodaira fibers are allowed
which lead to new breaking patterns of non-Abelian gauge groups.Comment: 53 pages, 9 figures, 6 tables. v2: references adde
Evidence-Based Dentistry: What's New?
The importance of evidence for every branch of medicine in teaching in order to orient the practitioners among the great amount of most actual scientific information's, and to support clinical decisions, is well established in health care, including dentistry
Extensions, expansions, Lie algebra cohomology and enlarged superspaces
After briefly reviewing the methods that allow us to derive consistently new
Lie (super)algebras from given ones, we consider enlarged superspaces and
superalgebras, their relevance and some possible applications.Comment: 9 pages. Invited talk delivered at the EU RTN Workshop, Copenhagen,
Sep. 15-19 and at the Argonne Workshop on Branes and Generalized Dynamics,
Oct. 20-24, 2003. Only change: wrong number of a reference correcte
Membranes for Topological M-Theory
We formulate a theory of topological membranes on manifolds with G_2
holonomy. The BRST charges of the theories are the superspace Killing vectors
(the generators of global supersymmetry) on the background with reduced
holonomy G_2. In the absence of spinning formulations of supermembranes, the
starting point is an N=2 target space supersymmetric membrane in seven
euclidean dimensions. The reduction of the holonomy group implies a twisting of
the rotations in the tangent bundle of the branes with ``R-symmetry'' rotations
in the normal bundle, in contrast to the ordinary spinning formulation of
topological strings, where twisting is performed with internal U(1) currents of
the N=(2,2) superconformal algebra. The double dimensional reduction on a
circle of the topological membrane gives the strings of the topological A-model
(a by-product of this reduction is a Green-Schwarz formulation of topological
strings). We conclude that the action is BRST-exact modulo topological terms
and fermionic equations of motion. We discuss the role of topological membranes
in topological M-theory and the relation of our work to recent work by Hitchin
and by Dijkgraaf et al.Comment: 22 pp, plain tex. v2: refs. adde
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