10 research outputs found
Free Differential Algebras and Pure Spinor Action in IIB Superstring Sigma Models
In this paper we extend to the case of IIB superstring sigma models the
method proposed in hep-th/10023500 to derive the pure spinor approach for type
IIA sigma models. In particular, starting from the (Free) Differential Algebra
and superspace parametrization of type IIB supergravity, extended to include
the BRST differential and all the ghosts, we derive the BRST transformations of
fields and ghosts as well as the standard pure spinor constraints for the
ghosts related to supersymmetry. Moreover, using the method first
proposed by us, we derive the pure spinor action for type IIB superstrings in
curved supergravity backgrounds (on shell), in full agreement with the action
first obtained by Berkovits and Howe.Comment: 24 page
Three-dimensional black holes from deformed anti-de Sitter
We present new exact three-dimensional black-string backgrounds, which
contain both NS--NS and electromagnetic fields, and generalize the BTZ black
holes and the black string studied by Horne and Horowitz. They are obtained as
deformations of the Sl(2,R) WZW model. Black holes resulting from purely
continuous deformations possess true curvature singularities. When discrete
identifications are introduced, extra chronological singularities appear, which
under certain circumstances turn out to be naked. The backgrounds at hand
appear in the moduli space of the Sl(2,R) WZW model. Hence, they provide exact
string backgrounds and allow for a more algebraical CFT description. This makes
possible the determination of the spectrum of primaries.Comment: JHEP style, 33 pages, 1 figur
Electric/Magnetic Deformations of S^3 and AdS_3, and Geometric Cosets
We analyze asymmetric marginal deformations of SU(2)_k and SL(2,R)_k WZW
models. These appear in heterotic string backgrounds with non-vanishing
Neveu--Schwarz three-forms plus electric or magnetic fields, depending on
whether the deformation is elliptic, hyperbolic or parabolic. Asymmetric
deformations create new families of exact string vacua. The geometries which
are generated in this way, deformed S^3 or AdS_3, include in particular
geometric cosets such as S^2, AdS_2 or H_2. Hence, the latter are consistent,
exact conformal sigma models, with electric or magnetic backgrounds. We discuss
various geometric and symmetry properties of the deformations at hand as well
as their spectra and partition functions, with special attention to the
supersymmetric AdS_2 x S^2 background. We also comment on potential holographic
applications.Comment: 38 pages, Added References. Aesthetic retouching
Towards a Holographic-Type Perspective in the Analysis of Complex-System Dynamics
By operating with the Scale Relativity Theory by means of two scenarios (Schrӧdinger and Madelung-type scenarios) in the dynamics of complex systems, we can achieve a description of these complex systems through a holographic-type perspective. Then, a gauge invariance of the Riccati type becomes functional in complex-system dynamics, which implies several consequences: conservation laws (in particular, for dynamics, the kinetic momentum conservation law), simultaneity and synchronization among the structural units’ (belonging to a complex system) dynamics, and temporal patterns through harmonic mappings. Finally, an economic case analysis is highlighted
Mathematical Modeling and Simulation in Mechanics and Dynamic Systems
The present book contains the 16 papers accepted and published in the Special Issue “Mathematical Modeling and Simulation in Mechanics and Dynamic Systems” of the MDPI “Mathematics” journal, which cover a wide range of topics connected to the theory and applications of Modeling and Simulation of Dynamic Systems in different field. These topics include, among others, methods to model and simulate mechanical system in real engineering. It is hopped that the book will find interest and be useful for those working in the area of Modeling and Simulation of the Dynamic Systems, as well as for those with the proper mathematical background and willing to become familiar with recent advances in Dynamic Systems, which has nowadays entered almost all sectors of human life and activity
String Theory: exact solutions, marginal deformations and hyperbolic spaces
This thesis is almost entirely devoted to studying string theory backgrounds
characterized by simple geometrical and integrability properties. The archetype
of this type of system is given by Wess-Zumino-Witten models, describing string
propagation in a group manifold or, equivalently, a class of conformal field
theories with current algebras. We study the moduli space of such models by
using truly marginal deformations. Particular emphasis is placed on asymmetric
deformations that, together with the CFT description, enjoy a very nice
spacetime interpretation in terms of the underlying Lie algebra. Then we take a
slight detour so to deal with off-shell systems. Using a renormalization-group
approach we describe the relaxation towards the symmetrical equilibrium
situation. In he final chapter we consider backgrounds with Ramond-Ramond field
and in particular we analyze direct products of constant-curvature spaces and
find solutions with hyperbolic spaces.Comment: PhD thesis, 168 page