1,243,110 research outputs found
Integrating Over Higgs Branches
We develop some useful techinques for integrating over Higgs branches in
supersymmetric theories with 4 and 8 supercharges. In particular, we define a
regularized volume for hyperkahler quotients. We evaluate this volume for
certain ALE and ALF spaces in terms of the hyperkahler periods. We also reduce
these volumes for a large class of hyperkahler quotients to simpler integrals.
These quotients include complex coadjoint orbits, instanton moduli spaces on
R^4 and ALE manifolds, Hitchin spaces, and moduli spaces of parabolic Higgs
bundles on Riemann surfaces. In the case of Hitchin spaces the evaluation of
the volume reduces to a summation over solutions of Bethe Ansatz equations for
the non-linear Schroedinger system. We discuss some applications of our
results.Comment: 32pp. harvmac big mode; v.2 34pp. typos fixed, sections 4.1, 5.2
substantially improve
Flat branches and pressure amorphization
After summarizing the phenomenology of pressure amorphization (PA), we
present a theory of PA based on the notion that one or more branches of the
phonon spectrum soften and flatten with increasing pressure. The theory
expresses the anharmonic dynamics of the flat branches in terms of local modes,
represented by lattice Wannier functions, which are in turn used to construct
an effective Hamiltonian. When the low-pressure structure becomes metastable
with respect to the high-pressure equilibrium phase and the relevant branches
are sufficiently flat, transformation into an amorphous phase is shown to be
kinetically favored because of the exponentially large number of both amorphous
phases and reaction pathways. In effect, the critical-size nucleus for the
first-order phase transition is found to be reduced to a single unit cell, or
nearly so. Random nucleation into symmetrically equivalent local configurations
characteristic of the high-pressure structure is then shown to overwhelm any
possible domain growth, and an ``amorphous'' structure results.Comment: 8 pages with 3 postscript figures embedded; Proceedings of the 4th
International Discussion Meeting on Relaxations in Complex Systems,
Hersonissos, Heraklion, Crete, June 16-23, ed. K. L. Ngai, Special Issues of
the Journal of Non-Crystalline Solids, 200
Novel Branches of (0,2) Theories
We show that recently proposed linear sigma models with torsion can be
obtained from unconventional branches of conventional gauge theories. This
observation puts models with log interactions on firm footing. If non-anomalous
multiplets are integrated out, the resulting low-energy theory involves log
interactions of neutral fields. For these cases, we find a sigma model geometry
which is both non-toric and includes brane sources. These are heterotic sigma
models with branes. Surprisingly, there are massive models with compact complex
non-Kahler target spaces, which include brane/anti-brane sources. The simplest
conformal models describe wrapped heterotic NS5-branes. We present examples of
both types.Comment: 36 pages, LaTeX, 2 figures; typo in Appendix fixed; references added
and additional minor change
Coulomb branches with complex singularities
We construct 4d superconformal field theories (SCFTs) whose Coulomb branches
have singular complex structures. This implies, in particular, that their
Coulomb branch coordinate rings are not freely generated. Our construction also
gives examples of distinct SCFTs which have identical moduli space (Coulomb,
Higgs, and mixed branch) geometries. These SCFTs thus provide an interesting
arena in which to test the relationship between moduli space geometries and
conformal field theory data.
We construct these SCFTs by gauging certain discrete global symmetries of
superYang-Mills (sYM) theories. In the simplest cases, these
discrete symmetries are outer automorphisms of the sYM gauge group, and so
these theories have lagrangian descriptions as sYM theories with
disconnected gauge groups.Comment: 43 page
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