347 research outputs found
Exact Ward-Takahashi identity for the lattice N=1 Wess-Zumino model
The lattice Wess-Zumino model written in terms of the Ginsparg-Wilson
relation is invariant under a generalized supersymmetry transformation which is
determined by an iterative procedure in the coupling constant. By studying the
associated Ward-Takahashi identity up to order we show that this lattice
supersymmetry automatically leads to restoration of continuum supersymmetry
without fine tuning. In particular, the scalar and fermion renormalization wave
functions coincide.Comment: 6 pages, 5 figures, Talk given at QG05, Cala Gonone, Sardinia, Italy.
12-16 September 200
The TASCC of Secretion
Author Manuscript 2012 July 05The oncogene-induced activation of signaling pathways involving the tumor suppressor proteins p53 and retinoblastoma is likely an important mechanism for preventing the proliferation of potential cancer cells (1, 2). This activation causes cells to exit the cell division cycle and enter a senescent state, which is characterized by major changes in chromatin structure that are thought to render senescence irreversible. Despite the absence of proliferation, senescent cells are not as quiescent as first thought, as they signal to their surrounding environment by activating a protein secretion program (3, 4). On page 966 of this issue, Narita et al. (5) show that to enable this secretory state, a senescent cell profoundly reorganizes its endomembrane system
Three Dimensional N=2 Supersymmetry on the Lattice
We show how 3-dimensional, N=2 supersymmetric theories, including super QCD
with matter fields, can be put on the lattice with existing techniques, in a
way which will recover supersymmetry in the small lattice spacing limit.
Residual supersymmetry breaking effects are suppressed in the small lattice
spacing limit by at least one power of the lattice spacing a.Comment: 21 pages, 2 figures, typo corrected, reference adde
About the realization of chiral symmetry in QCD2
Two dimensional massless Quantum Chromodynamics presents many features which
resemble those of the true theory. In particular the spectrum consists of
mesons and baryons arranged in flavor multiplets without parity doubling. We
analyze the implications of chiral symmetry, which is not spontaneously broken
in two dimensions, in the spectrum and in the quark condensate. We study how
parity doubling, an awaited consequence of Coleman's theorem, is avoided due to
the dimensionality of space-time and confinement. We prove that a chiral phase
transition is not possible in the theory.Comment: 9 pages, latex, ftuv/92-
Spin-Pseudospin Coherence and CP Skyrmions in Bilayer Quantum Hall Ferromagnets
We analyze bilayer quantum Hall ferromagnets, whose underlying symmetry group
is SU(4). Spin-pseudospin coherence develops spontaneously when the total
electron density is low enough. Quasiparticles are CP^3 skyrmions. One skyrmion
induces charge modulations on both of the two layers. At the filling factor one elementary excitation consists of a pair of skyrmions and its charge
is . Recent experimental data due to Sawada et al. [Phys. Rev. Lett. {\bf
80}, 4534 (1998)] support this conclusion.Comment: 4 pages including 2 figures (published version
The massive model for frustrated spin systems
We study the classical Non Linear
Sigma model which is the continuous low energy effective field theory for
component frustrated spin systems. The functions for the two coupling
constants of this model are calculated around two dimensions at two loop order
in a low temperature expansion. Our study is completed by a large analysis
of the model. The functions for the coupling constants and the mass gap
are calculated in all dimensions between 2 and 4 at order . As a main
result we show that the standard procedure at the basis of the expansion
leads to results that partially contradict those of the weak coupling analysis.
We finally present the procedure that reconciles the weak coupling and large
analysis, giving a consistent picture of the expected scaling of frustrated
magnets.Comment: 55 pages, Late
Matrix formulation of superspace on 1D lattice with two supercharges
Following the approach developed by some of the authors in recent papers and
using a matrix representation for the superfields, we formulate an exact
supersymmetric theory with two supercharges on a one dimensional lattice. In
the superfield formalism supersymmetry transformations are uniquely defined and
do not suffer of the ambiguities recently pointed out by some authors. The
action can be written in a unique way and it is invariant under all
supercharges. A modified Leibniz rule applies when supercharges act on a
superfield product and the corresponding Ward identities take a modified form
but hold exactly at least at the tree level, while their validity in presence
of radiative corrections is still an open problem and is not considered here.Comment: 25 page
The Expansion and Spin Correlations in Constrained Wavefunctions
We develop a large-N expansion for Gutzwiller projected spin states. We
consider valence bonds singlets, constructed by Schwinger bosons or fermions,
which are variational ground states for quantum antiferromagnets. This
expansion is simpler than the familiar expansions of the quantum Heisenberg
model, and thus more instructive. The diagrammatic rules of this expansion
allow us to prove certain identities to all orders in 1/N. We derive the
on-site spin fluctuations sum rule for arbitrary N. We calculate the
correlations of the one dimensional Valence Bonds Solid states and the
Gutzwiller Projected Fermi Gas upto order 1/N. For the bosons case, we are
surprised to find that the mean field, the order 1/N and the exact correlations
are simply proportional. For the fermions case, the 1/N correction enhances the
zone edge singularity. The comparison of our leading order terms to known
results for N=2, enhances our understanding of large-N approximations in
general.Comment: 36 pages, LaTe
Four Dimensional Black Holes in String Theory
Exact solutions of heterotic string theory corresponding to four-dimensional
charge Q magnetic black holes are constructed as tensor products of an
SU(2)/Z(2Q+2) WZW orbifold with a (0,1) supersymmetric SU(1,1)/U(1) WZW coset
model. The spectrum is analyzed in some detail. ``Bad'' marginal operators are
found which are argued to deform these theories to asymptotically flat black
holes. Surprising behaviour is found for small values of Q, where low-energy
field theory is inapplicable. At the minimal value Q=1, the theory degenerates.
Renormalization group arguments are given that suggest the potential
gravitational singularity of the low-energy field theory is resolved by a
massive two-dimensional field theory. At Q=0, a stable, neutral ``remnant,'' of
potential relevance to the black hole information paradox, is found.Comment: 37 pages + 1 figure (tar compressed and uuencoded
Exact Solutions of Berkovits' String Field Theory
The equation of motion for Berkovits' WZW-like open (super)string field
theory is shown to be integrable in the sense that it can be written as the
compatibility condition ("zero-curvature condition") of some linear equations.
Employing a generalization of solution-generating techniques (the splitting and
the dressing methods), we demonstrate how to construct nonperturbative
classical configurations of both N=1 superstring and N=2 fermionic string field
theories. With and without u(n) Chan-Paton factors, various solutions of the
string field equation are presented explicitly.Comment: 1+20 pages, LaTeX; v2: typos fixed, version to appear in Nucl. Phys.
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