Cohomological analysis of bosonic D-strings and 2d sigma models coupled to abelian gauge fields

We analyse completely the BRST cohomology on local functionals for two dimensional sigma models coupled to abelian world sheet gauge fields, including effective bosonic D-string models described by Born-Infeld actions. In particular we prove that the rigid symmetries of such models are exhausted by the solutions to generalized Killing vector equations which we have presented recently, and provide all the consistent first order deformations and candidate gauge anomalies of the models under study. For appropriate target space geometries we find nontrivial deformations both of the abelian gauge transformations and of the world sheet diffeomorphisms, and antifield dependent candidate anomalies for both types of symmetries separately, as well as mixed ones.Comment: 41 pages, latex, no figures; change of title and abstract, some comments added; to appear in Nucl. Phys.

Multigrid Methods in Lattice Field Computations

The multigrid methodology is reviewed. By integrating numerical processes at all scales of a problem, it seeks to perform various computational tasks at a cost that rises as slowly as possible as a function of $n$, the number of degrees of freedom in the problem. Current and potential benefits for lattice field computations are outlined. They include: $O(n)$ solution of Dirac equations; just $O(1)$ operations in updating the solution (upon any local change of data, including the gauge field); similar efficiency in gauge fixing and updating; $O(1)$ operations in updating the inverse matrix and in calculating the change in the logarithm of its determinant; $O(n)$ operations per producing each independent configuration in statistical simulations (eliminating CSD), and, more important, effectively just $O(1)$ operations per each independent measurement (eliminating the volume factor as well). These potential capabilities have been demonstrated on simple model problems. Extensions to real life are explored.Comment: 4

One Dimensional Continuum Falicov-Kimball Model in the Strongly Correlated Limit

In this paper we study the thermodynamics of the one dimensional continuum analogue of the Falicov-Kimball model in the strongly correlated limit using a method developed by Salsburg, Zwanzig and Kirkwood for the Takahashi gas. In the ground state it is found that the $f$ electrons form a cluster. The effect of including a Takahashi repulsion between $f$ particles is also studied where it is found that as the repulsion is increased the ground state $f$ electron configuration changes discontinuously from the clustered configuration to a homogeneous or equal spaced configuration analogous to the checkerboard configuration which arises in the lattice Falicov-Kimball model.Comment: 17 pages, Standard Latex File (UUencoded Postscript file of figures available upon request. To appear in physica A) MELB-MATHS-PP-1096783, email: [email protected]

Actions and symmetries of NSR superstrings and D-strings

We present all NSR superstring and super-D-string actions invariant under a set of prescribed gauge transformations, and characterize completely their global symmetries. In particular we obtain locally supersymmetric Born-Infeld actions on general backgrounds in a formulation with extra target space dimensions. The nontrivial global symmetries of the superstring actions correspond to isometries of the background, whereas super-D-string actions can have additional symmetries acting nontrivially also on the coordinates of the extra dimensions.Comment: 4 pages, references added and errors correcte

Perceived Vertical and Lateropulsion: Clinical Syndromes, Localization, and Prognosis

We present a clinical classification of central vestibular syndromes according to the three major planes of action of the vestibulo-ocular reflex: yaw, roll, and pitch. The plane-specific syndromes are determined by ocular motor, postural, and percep tual signs. Yaw plane signs are horizontal nystagmus, past pointing, rotational and lat eral body falls, deviation of perceived straight-ahead to the left or right. Roll plane signs are torsional nystagmus, skew deviation, ocular torsion, tilts of head, body, and perceived vertical in a clockwise or counterclockwise direction. Pitch plane signs are upbeat/downbeat nystagmus, forward/backward tilts and falls, deviations of the per ceived horizon. The thus defined vestibular syndromes allow a precise topographic analysis of brainstem lesions according to their level and side. Special emphasis is placed on the vestibular roll plane syndromes of ocular tilt reaction, lateropulsion in Wallenberg's syndrome, thalamic and cortical astasia and their association with roll plane tilt of perceived vertical. Recovery is based on a functionally significant central compensation of a vestibular tone imbalance, the mechanism of which is largely un known. Physical therapy may facilitate this central compensation, but this has not yet been proven in prospective studies

Dynamical susceptibilities in strong coupling approach

A general scheme to calculate dynamical susceptibilities of strongly correlated electron systems within the dynamical mean field theory is developed. Approach is based on an expansion over electron hopping around the atomic limit (within the diagrammatic technique for site operators: projection and Hubbard ones) in infinite dimensions. As an example, the Falicov-Kimball and simplified pseudospin-electron models are considered for which an analytical expressions for dynamical susceptibilities are obtained.Comment: 2 pages, 3 eps figures, final version published in proceedings of M2S-HTSC-VI (Houston

Hard Thermal Loops in the n-Dimensional phi3 Theory

We derive a closed-form result for the leading thermal contributions which appear in the n-dimensional phi3 theory at high temperature. These contributions become local only in the long wavelength and in the static limits, being given by different expressions in these two limits.Comment: 3 pages, one figure. To be published in the Brazilian Journal of Physic

Anomalous Magnetic Moment of Electron in Chern-Simons QED

We calculate the anomalous magnetic moment of the electron in the Chern-Simons theory in 2+1 dimensions with and without a Maxwell term, both at zero temperature as well as at finite temperature. In the case of the Maxwell-Chern-Simons (MCS) theory, we find that there is an infrared divergence, both at zero as well as at finite temperature, when the tree level Chern-Simons term vanishes, which suggests that a Chern-Simons term is essential in such theories. At high temperature, the thermal correction in the MCS theory behaves as $\frac{1}{\beta} \ln \beta M$, where $\beta$ denotes the inverse temperature and $M$, the Chern-Simons coefficient. On the other hand, we find no thermal correction to the anomalous magnetic moment in the pure Chern-Simons (CS) theory.Comment: 13 pages, 2 figure

Supersymmetry algebra cohomology II: Primitive elements in 2 and 3 dimensions

The primitive elements of the supersymmetry algebra cohomology as defined in a companion paper are computed exhaustively for standard supersymmetry algebras in dimensions D=2 and D=3, for all signatures (t,D-t) and all numbers N of sets of supersymmetries.Comment: 19 pages; v3: matches published version; presentation of D=3 analysis streamlined; presentation of lemmas 2.3 and 2.5 improved; minor correction of misprints; minor change of titl

B\"acklund Transformations an Zero-Curvature Representations of Systems of Partial Differential Equations

It is shown that B\"acklund transformations (BTs) and zero-curvature representations (ZCRs) of systems of partial differential equations (PDEs) are closely related. The connection is established by nonlinear representations of the symmetry group underlying the ZCR which induce gauge transformations relating different BTs. This connection is used to construct BTs from ZCRs (and vice versa). Furthermore a procedure is outlined which allows a systematic search for ZCRs of a given system of PDEs.Comment: 25 page