830 research outputs found
Wilson Fermions on a Randomly Triangulated Manifold
A general method of constructing the Dirac operator for a randomly
triangulated manifold is proposed. The fermion field and the spin connection
live, respectively, on the nodes and on the links of the corresponding dual
graph. The construction is carried out explicitly in 2-d, on an arbitrary
orientable manifold without boundary. It can be easily converted into a
computer code. The equivalence, on a sphere, of Majorana fermions and Ising
spins in 2-d is rederived. The method can, in principle, be extended to higher
dimensions.Comment: 18 pages, latex, 6 eps figures, fig2 corrected, Comment added in the
conclusion sectio
Novel field theory phenomena from F theory and D-branes
Talk presented in the 97 Karpatcz winter school. We describe Sen's work on F
theory on K3 and its reflection on the world-volume field theory on a D3-brane
probe. Field theories on a multiple of probes are analyzed. We construct a 4d
N=1 superconformal probe theory which is invariant under electric-magnetic
duality via a compactification to six dimensions on T^6/Z_2 x Z_2.Comment: latex file, 14 pages, 15 figs, epsf.sty, espcrc2.st
Supersymmetric Three-cycles and (Super)symmetry Breaking
We describe physical phenomena associated with a class of transitions that
occur in the study of supersymmetric three-cycles in Calabi-Yau threefolds. The
transitions in question occur at real codimension one in the complex structure
moduli space of the Calabi-Yau manifold. In type IIB string theory, these
transitions can be used to describe the evolution of a BPS state as one moves
through a locus of marginal stability: at the transition point the BPS particle
becomes degenerate with a supersymmetric two particle state, and after the
transition the lowest energy state carrying the same charges is a
non-supersymmetric two particle state. In the IIA theory, wrapping the cycles
in question with D6-branes leads to a simple realization of the Fayet model:
for some values of the CY modulus gauge symmetry is spontaneously broken, while
for other values supersymmetry is spontaneously broken.Comment: 10 pages, harvmac big; v2, minor change
Distribution of satellite galaxies in high redshift groups
We use galaxy groups at redshifts between 0.4 and 1.0 selected from the Great
Observatories Origins Deep Survey (GOODS) to study the color-morphological
properties of satellite galaxies, and investigate possible alignment between
the distribution of the satellites and the orientation of their central galaxy.
We confirm the bimodal color and morphological type distribution for satellite
galaxies at this redshift range: the red and blue classes corresponds to the
early and late morphological types respectively, and the early-type satellites
are on average brighter than the late-type ones. Furthermore, there is a {\it
morphological conformity} between the central and satellite galaxies: the
fraction of early-type satellites in groups with an early-type central is
higher than those with a late-type central galaxy. This effect is stronger at
smaller separations from the central galaxy. We find a marginally significant
signal of alignment between the major axis of the early-type central galaxy and
its satellite system, while for the late-type centrals no significant alignment
signal is found. We discuss the alignment signal in the context of shape
evolution of groups.Comment: 7 pages, 7 figures, accepted by Ap
On the Lagrangian Realization of Non-Critical -Strings
A large class of non-critical string theories with extended worldsheet gauge
symmetry are described by two coupled, gauged Wess-Zumino-Witten Models. We
give a detailed analysis of the gauge invariant action and in particular the
gauge fixing procedure and the resulting BRST symmetries. The results are
applied to the example of strings.Comment: 19 pages, LaTeX (REVTEX macro's
Gauge theory, topological strings, and S-duality
We offer a derivation of the duality between the topological U(1) gauge
theory on a Calabi-Yau 3-fold and the topological A-model on the same manifold.
This duality was conjectured recently by Iqbal, Nekrasov, Okounkov, and Vafa.
We deduce it from the S-duality of the IIB superstring. We also argue that the
mirror version of this duality relates the topological B-model on a Calabi-Yau
3-fold and a topological sector of the Type IIA Little String Theory on the
same manifold.Comment: 9 pages, latex. v2: a footnote has been added. The footnote corrects
an inaccuracy in the original argument; the results are unchanged. v3:
exposition improve
Black Hole Attractors and the Topological String
A simple relationship of the form Z_BH = |Z_top|^2 is conjectured, where Z_BH
is a supersymmetric partition function for a four-dimensional BPS black hole in
a Calabi-Yau compactification of Type II superstring theory and Z_top is a
second-quantized topological string partition function evaluated at the
attractor point in moduli space associated to the black hole charges. Evidence
for the conjecture in a perturbation expansion about large graviphoton charge
is given. The microcanonical ensemble of BPS black holes can be viewed as the
Wigner function associated to the wavefunction defined by the topological
string partition function.Comment: 32 pages, harvma
Euler number of Instanton Moduli space and Seiberg-Witten invariants
We show that a partition function of topological twisted N=4 Yang-Mills
theory is given by Seiberg-Witten invariants on a Riemannian four manifolds
under the condition that the sum of Euler number and signature of the four
manifolds vanish. The partition function is the sum of Euler number of
instanton moduli space when it is possible to apply the vanishing theorem. And
we get a relation of Euler number labeled by the instanton number with
Seiberg-Witten invariants, too. All calculation in this paper is done without
assuming duality.Comment: LaTeX, 34 page
Quantum Group Generators in Conformal Field Theory
These are notes of a seminar given at the 30th International Symposium on the
Theory of Elementary Particles, Berlin-Buckow, August 1996. The material is
derived from collaborations with E. Cremmer and J.-L. Gervais, and C. Klimcik,
and is partially new. Within the general framework of Poisson-Lie symmetry, we
discuss two approaches to the problem of constructing moment maps, or
q-deformed Noether charges, that generate the quantum group symmetry which
appears in many conformal field theories. Concretely, we consider the case of
and the operator algebra that describes Liouville theory and other
models built from integer powers of screenings in the Coulomb gas picture.Comment: 21 pages, LaTe
Multivalued Fields on the Complex Plane and Conformal Field Theories
In this paper a class of conformal field theories with nonabelian and
discrete group of symmetry is investigated. These theories are realized in
terms of free scalar fields starting from the simple systems and scalar
fields on algebraic curves. The Knizhnik-Zamolodchikov equations for the
conformal blocks can be explicitly solved. Besides of the fact that one obtains
in this way an entire class of theories in which the operators obey a
nonstandard statistics, these systems are interesting in exploring the
connection between statistics and curved space-times, at least in the two
dimensional case.Comment: (revised version), 30 pages + one figure (not included), (requires
harvmac.tex), LMU-TPW 92-1
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