424 research outputs found
One-loop Beta Functions for the Orientable Non-commutative Gross-Neveu Model
We compute at the one-loop order the beta-functions for a renormalisable
non-commutative analog of the Gross Neveu model defined on the Moyal plane. The
calculation is performed within the so called x-space formalism. We find that
this non-commutative field theory exhibits asymptotic freedom for any number of
colors. The beta-function for the non-commutative counterpart of the Thirring
model is found to be non vanishing.Comment: 16 pages, 9 figure
Bosonized noncommutative bi-fundamental fermion and S-duality
We perform the path-integral bosonization of the recently proposed
noncommutative massive Thirring model (NCMT) [JHEP0503(2005)037]. This
model presents two types of current-current interaction terms related to the
bi-fundamental representation of the group U(1). Firstly, we address the
bosonization of a bi-fundamental free Dirac fermion defined on a noncommutative
(NC) Euclidean plane \IR_{\theta}^{2}. In this case we show that the fermion
system is dual to two copies of the NC Wess-Zumino-Novikov-Witten model. Next,
we apply the bosonization prescription to the NCMT model living on
\IR_{\theta}^{2} and show that this model is equivalent to two-copies of the
WZNW model and a two-field potential defined for scalar fields corresponding to
the global symmetry plus additional bosonized terms for the
four fermion interactions. The bosonic sector resembles to the one proposed by
Lechtenfeld et al. [Nucl. Phys. B705(2005)477] as the noncommutative
sine-Gordon for a {\sl pair} of scalar fields. The bosonic and fermionic
couplings are related by a strong-weak duality. We show that the couplings of
the both sectors for some representations satisfy similar relationships up to
relevant re-scalings, thus the NC bi-fundamental couplings are two times the
corresponding ones of the NC fundamental (anti-fundamental) and eight times the
couplings of the ordinary massive Thirring and sine-Gordon models.Comment: 18 pages, LaTex. References added. A general product has been considered in the conclusion section . Version to appear in
JHE
Women Do Not Report the Violence They Suffer: Violence Against Women and the State Action Doctrine
No Exit? Withdrawal Rights and the Law of Corporate Reorganizations
Bankruptcy scholarship is largely a debate about the comparative merits of a mandatory regime on one hand and bankruptcy by free design on the other. By the standard account, the current law of corporate reorganization is mandatory. Various rules that cannot be avoided ensure that investorsâ actions are limited and they do not exercise their rights against specialized assets in a way that destroys the value of a business as a whole. These rules solve collective action problems and reduce the risk of bargaining failure. But there are costs to a mandatory regime. In particular, investors cannot design their rights to achieve optimal monitoring as they could in a system of bankruptcy by free design. This Article suggests that the academic debate has missed a fundamental feature of the law. Bankruptcy operates on legal entities, not on firms in the economic sense. For this reason, sophisticated investors do not face a mandatory regime at all. The ability of investors to place assets in separate entities gives them the ability to create specific withdrawal rights in the event the firm encounters financial distress. There is nothing mandatory about rules like the automatic stay when assets can be partitioned off into legal entities that are beyond the reach of the bankruptcy judge. Thus, by partitioning assets of one economic enterprise into different legal entities, investors can create a tailored bankruptcy regime. In this way, legal entities serve as building blocks that can be combined to create specific and varied but transparent investor withdrawal rights. This regime of tailored bankruptcy has been unrecognized and underappreciated and may be preferable to both mandatory and free design regimes. By allowing a limited number of investors to opt out of bankruptcy in a particular, discrete, and visible way, investors as a group may be able to both limit the risk of bargaining failure and at the same time enjoy the disciplining effect that a withdrawal right brings with it
Is There A String Theory Landscape
We examine recent claims of a large set of flux compactification solutions of
string theory. We conclude that the arguments for AdS solutions are plausible.
The analysis of meta-stable dS solutions inevitably leads to situations where
long distance effective field theory breaks down. We then examine whether these
solutions are likely to lead to a description of the real world. We conclude
that one must invoke a strong version of the anthropic principle. We explain
why it is likely that this leads to a prediction of low energy supersymmetry
breaking, but that many features of anthropically selected flux
compactifications are likely to disagree with experiment.Comment: 39 pages, Latex, ``Terminology surrounding the anthropic principle
revised to conform with accepted usage. More history of the anthropic
principle included. Various references added.
Bounds on masses of bulk fields in string compactifications
In string compactification on a manifold X, in addition to the string scale
and the normal scales of low-energy particle physics, there is a Kaluza-Klein
scale 1/R associated with the size of X. We present an argument that generic
string models with low-energy supersymmetry have, after moduli stabilization,
bulk fields with masses which are parametrically lighter than 1/R. We discuss
the implications of these light states for anomaly mediation and gaugino
mediation scenarios.Comment: 15 page
- âŠ