2,483 research outputs found
On the Landau-Ginzburg Realization of Topological Gravities
We study the equivariant cohomology of a class of multi-field topological LG
models, and find that such systems carry intrinsic information about
-gravity. As a result, we can construct the gravitational chiral ring in
terms of LG polynomials. We find, in particular, that the spectrum of such
theories seems to be richer than so far expected. We also briefly discuss the
BRST operator for non-linear topological -gravity.Comment: 26p, harvmac, 4 uuencoded PostScript figure
K3--Fibrations and Heterotic-Type II String Duality
We analyze the map between heterotic and type II N=2 supersymmetric string
theories for certain two and three moduli examples found by Kachru and Vafa.
The appearance of elliptic j-functions can be traced back to specializations of
the Picard-Fuchs equations to systems for surfaces. For the three-moduli
example we write the mirror maps and Yukawa couplings in the weak coupling
limit in terms of j-functions; the expressions agree with those obtained in
perturbative calculations in the heterotic string in an impressive way. We also
discuss symmetries of the world-sheet instanton numbers in the type II theory,
and interpret them in terms of S--duality of the non-perturbative heterotic
string.Comment: 16p, harvmac with hyperlink
Topological Strings from WZW Models
We show that the BRST structure of the topological string is encoded in the
``small'' superconformal algebra, enabling us to obtain, in a non-trivial
way, the string theory from hamiltonian reduction of . This leads to
the important conclusion that not only ordinary string theories, but
topological strings as well, can be obtained, or even defined, by hamiltonian
reduction from WZW models. Using two different gradations, we find either the
standard minimal models coupled to topological gravity, or an embedding
of the bosonic string into the topological string. We also comment briefly on
the generalization to super Lie algebras .Comment: 14p, late
Nonperturbative Effective Actions of N=2 Supersymmetric Gauge Theories
We elaborate on our previous work on N=2 supersymmetric Yang-Mills theory. In
particular, we show how to explicitly determine the low energy quantum
effective action for from the underlying hyperelliptic Riemann
surface, and calculate the leading instanton corrections. This is done by
solving Picard-Fuchs equations and asymptotically evaluating period integrals.
We find that the dynamics of the theory is governed by an Appell system
of type , and compute the exact quantum gauge coupling explicitly in terms
of Appell functions.Comment: 57p, harvmac with hyperlinks, 9 uuencoded ps figure
On the Monodromies of N=2 Supersymmetric Yang-Mills Theory
We review the generalization of the work of Seiberg and Witten on N=2
supersymmetric SU(2) Yang-Mills theory to SU(n) gauge groups. The quantum
moduli spaces of the effective low energy theory parametrize a special family
of hyperelliptic genus n-1 Riemann surfaces. We discuss the massless spectrum
and the monodromies.Comment: 15p, harvmac/lanlmac with hyperlinks, 4 uuencoded compressed
postscript figures appende
Picard-Fuchs Equations and Special Geometry
We investigate the system of holomorphic differential identities implied by
special K\"ahlerian geometry of four-dimensional N=2 supergravity. For
superstring compactifications on \cy threefolds these identities are equivalent
to the Picard-Fuchs equations of algebraic geometry that are obeyed by the
periods of the holomorphic three-form. For one variable they reduce to linear
fourth-order equations which are characterized by classical -generators; we
find that the instanton corrections to the Yukawa couplings are directly
related to the non-vanishing of . We also show that the symplectic
structure of special geometry can be related to the fact that the Yukawa
couplings can be written as triple derivatives of some holomorphic function
. Moreover, we give the precise relationship of the Yukawa couplings of
special geometry with three-point functions in topological field theory.Comment: 43 page
On Heterotic/Type I Duality in d=8
We discuss heterotic corrections to quartic internal U(1) gauge couplings and
check duality by calculating one-loop open string diagrams and identifying the
D-instanton sum in the dual type I picture. We also compute SO(8)^4 threshold
corrections and finally R^2 corrections in type I theory.Comment: 9 pages, Latex, To appear in the proceedings of "Quantum Aspects of
Gauge Theories, Supersymmetries and Unification", Corfu, September 199
Toric complete intersections and weighted projective space
It has been shown by Batyrev and Borisov that nef partitions of reflexive
polyhedra can be used to construct mirror pairs of complete intersection
Calabi--Yau manifolds in toric ambient spaces. We construct a number of such
spaces and compute their cohomological data. We also discuss the relation of
our results to complete intersections in weighted projective spaces and try to
recover them as special cases of the toric construction. As compared to
hypersurfaces, codimension two more than doubles the number of spectra with
. Alltogether we find 87 new (mirror pairs of) Hodge data, mainly
with .Comment: 16 pages, LaTeX2e, error in Hodge data correcte
Free-field Representations and Geometry of some Gepner models
The geometry of Gepner model, where is investigated by
free-field representation known as "bc\bet\gm"-system. Using this
representation it is shown directly that internal sector of the model is given
by Landau-Ginzburg -orbifold. Then we consider
the deformation of the orbifold by marginal anti-chiral-chiral operator.
Analyzing the holomorphic sector of the deformed space of states we show that
it has chiral de Rham complex structure of some toric manifold, where toric
dates are given by certain fermionic screening currents. It allows to relate
the Gepner model deformed by the marginal operator to the -model on CY
manifold realized as double cover of with ramification along
certain submanifold.Comment: LaTex, 14 pages, some acknowledgments adde
Diffusive electron acceleration at SNR shock fronts and the observed SNR radio spectral indices
The radio synchrotron emission from relativistic electrons in shell supernova remnants (SNRs) provides a unique opportunity to probe the energy distribution of energetic electrons at their acceleration site (SNR shock fronts). This information provides insight into the acceleration mechanism(s). The implications of these observations for the diffusive (first-order Fermi) acceleration of electrons at the SNR shock fronts are discussed
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