53 research outputs found
Nilpotent Marsh and SUSY QM
We consider the nilpotent additions to classical trajectories in
supersymmetric and nonsupersymmetric theories. The condition of anilpotence of
action on some generalized solutions leads to the Witten supersymmetric
Lagrangian. The condition of anilpotence of topological charge is the same as
one of superpotential with spontaneous broken supersymmetry. We should vanish
half of Grassmann constants of integration, because in this case only we obtain
the same number of normalized bosonic and fermionic zero modes.Comment: 8 pages, Latex 2.09. Talk given at the conference in memory of V.I.
Ogievetski, Dubna, July, 1997. To be published in the Proceeding
Duals of noncommutative supersymmetric U(1) gauge theory
Parent actions for component fields are utilized to derive the dual of
supersymmetric U(1) gauge theory in 4 dimensions. Generalization of the
Seiberg-Witten map to the component fields of noncommutative supersymmetric
U(1) gauge theory is analyzed. Through this transformation we proposed parent
actions for noncommutative supersymmetric U(1) gauge theory as generalization
of the ordinary case.Duals of noncommutative supersymmetric U(1) gauge theory
are obtained. Duality symmetry under the interchange of fields with duals
accompanied by the replacement of the noncommutativity parameter
\Theta_{\mu\nu} with \tilde{\Theta}_{\mu \nu} =
\epsilon_{\mu\nu\rho\sigma}\Theta^{\rho\sigma} of the non--supersymmetric case
is broken at the level of actions. We proposed a noncommutative parent action
for the component fields which generates actions possessing this duality
symmetry.Comment: Typos corrected. Version which will appear in JHE
On the relation between effective supersymmetric actions in different dimensions
We make two remarks: (i) Renormalization of the effective charge in a
4--dimensional (supersymmetric) gauge theory is determined by the same graphs
and is rigidly connected to the renormalization of the metric on the moduli
space of the classical vacua of the corresponding reduced quantum mechanical
system. Supersymmetry provides constraints for possible modifications of the
metric, and this gives us a simple proof of nonrenormalization theorems for the
original 4-dimensional theory. (ii) We establish a nontrivial relationship
between the effective (0+1)-dimensional and (1+1)-dimensional Lagrangia (the
latter represent conventional
Kahlerian sigma models).Comment: 15 pages, 2 figure
On the Supergravity Gauge theory Correspondence and the Matrix Model
We review the assumptions and the logic underlying the derivation of DLCQ
Matrix models. In particular we try to clarify what remains valid at finite
, the role of the non-renormalization theorems and higher order terms in the
supergravity expansion. The relation to Maldacena's conjecture is also
discussed. In particular the compactification of the Matrix model on is
compared to the super Yang-Mills duality, and
the different role of the branes in the two cases is pointed out.Comment: 19 pages, Late
Cosmological Perturbations in Flux Compactifications
Kaluza-Klein compactifications with four-dimensional inflationary geometry
combine the attractive idea of higher dimensional models with the attempt to
incorporate four-dimensional early-time or late-time cosmology. We analyze the
mass spectrum of cosmological perturbations around such compactifications,
including the scalar, vector, and tensor sector. Whereas scalar perturbations
were discussed before, the spectrum of vector and tensor perturbations is a new
result of this article. Moreover, the complete analysis shows, that possible
instabilities of such compactifications are restricted to the scalar sector.
The mass squares of the vector and tensor perturbations are all non-negative.
We discuss form fields with a non-trivial background flux in the extra space as
matter degrees of freedom. They provide a source of scalar and vector
perturbations in the effective four-dimensional theory. We analyze the
perturbations in Freund-Rubin compactifications. Although it can only be
considered as a toy model, we expect the results to qualitatively generalize to
similar configurations. We find that there are two possible channels of
instabilities in the scalar sector of perturbations, whose stabilization has to
be addressed in any cosmological model that incorporates extra dimensions und
form fields. One of the instabilities is associated with the perturbations of
the form field.Comment: 16 pages, v2 figure and references added, accepted version for JCA
Eleven-dimensional massless superparticles and matrix theory spin-orbit couplings revisited
The classical probe dynamics of the eleven-dimensional massless
superparticles in the background geometry produced by N source M-momenta is
investigated in the framework of N-sector DLCQ supergravity. We expand the
probe action up to the two fermion terms and find that the fermionic
contributions are the spin-orbit couplings, which precisely agree with the
matrix theory calculations. We comment on the lack of non-perturbative
corrections in the one-loop matrix quantum mechanics effective action and its
compatibility with the supergravity analysis.Comment: 11 pages, Latex, no figure
Japanese Encephalitis Outbreak, India, 2005
An outbreak of viral encephalitis occurred in Gorakhpur, India, from July through November 2005. The etiologic agent was confirmed to be Japanese encephalitis virus by analyzing 326 acute-phase clinical specimens for virus-specific antibodies and viral RNA and by virus isolation. Phylogenetic analysis showed that these isolates belonged to genogroup 3
D-instantons and Matrix Models
We discuss the Matrix Model aspect of configurations saturating a fixed
number of fermionic zero modes. This number is independent of the rank of the
gauge group and the instanton number. This will allow us to define a
large- limit of the embeddeding of D-instantons in the Matrix Model
and make contact with the leading term (the measure factor) of the supergravity
computations of D-instanton effects. We show that the connection between these
two approaches is done through the Abelian modes of the Matrix variables.Comment: harvmac (b), 26 pages. v5 : polished final version for publication.
Cosmetic changes onl
M(atrix) Theory: Matrix Quantum Mechanics as a Fundamental Theory
A self-contained review is given of the matrix model of M-theory. The
introductory part of the review is intended to be accessible to the general
reader. M-theory is an eleven-dimensional quantum theory of gravity which is
believed to underlie all superstring theories. This is the only candidate at
present for a theory of fundamental physics which reconciles gravity and
quantum field theory in a potentially realistic fashion. Evidence for the
existence of M-theory is still only circumstantial---no complete
background-independent formulation of the theory yet exists. Matrix theory was
first developed as a regularized theory of a supersymmetric quantum membrane.
More recently, the theory appeared in a different guise as the discrete
light-cone quantization of M-theory in flat space. These two approaches to
matrix theory are described in detail and compared. It is shown that matrix
theory is a well-defined quantum theory which reduces to a supersymmetric
theory of gravity at low energies. Although the fundamental degrees of freedom
of matrix theory are essentially pointlike, it is shown that higher-dimensional
fluctuating objects (branes) arise through the nonabelian structure of the
matrix degrees of freedom. The problem of formulating matrix theory in a
general space-time background is discussed, and the connections between matrix
theory and other related models are reviewed.Comment: 56 pages, 3 figures, LaTeX, revtex style; v2: references adde
Detecting dynamic changes in modular organization of spontaneous brain activity A preliminary study
International audienceOur brain is a dynamic modular network. Even at rest, brain networks dynamically reconfigure in an organized manner, establishing patterns of connectivity known as resting state networks (RSNs). Recently, significant efforts have been devoted to characterize the dynamics of RSNs. However, little is known about how the dynamic changes in the modular structure shapes the fast spontaneous activity. In this paper, our objective is to validate the feasibility of a recently proposed modularity-based algorithm in investigating RSNs and their variations over time. For this aim, EEG data were recorded from two subjects during resting state. Using EEG source connectivity method with a sliding window, we reconstructed the dynamic brain networks in alpha band. Then, we applied the modularity algorithm to identify the main modular brain states fluctuating over time. The dominant modules were associated with the RSNs. Results showed that the extracted modules were concordant with RSNs found in literature. In particular, the default mode network, known as the most consistent RSN, dynamically alternates its reconfiguration between three modular organizations. Overall, we speculate that this approach, when applied on a larger dataset, will give new insights about the dynamic behavior of RSNs. © 2019 IEEE
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