7,723 research outputs found
Absence of a fuzzy phase in the dimensionally reduced 5d Yang-Mills-Chern-Simons model
We perform nonperturbative studies of the dimensionally reduced 5d
Yang-Mills-Chern-Simons model, in which a four-dimensional fuzzy manifold,
``fuzzy S'', is known to exist as a classical solution. Although the
action is unbounded from below, Monte Carlo simulations provide an evidence for
a well-defined vacuum, which stabilizes at large , when the coefficient of
the Chern-Simons term is sufficiently small. The fuzzy S prepared as an
initial configuration decays rapidly into this vacuum in the process of
thermalization. Thus we find that the model does not possess a ``fuzzy S
phase'' in contrast to our previous results on the fuzzy S.Comment: 11 pages, 2 figures, (v2) typos correcte
UV/IR duality in noncommutative quantum field theory
We review the construction of renormalizable noncommutative euclidean
phi(4)-theories based on the UV/IR duality covariant modification of the
standard field theory, and how the formalism can be extended to scalar field
theories defined on noncommutative Minkowski space.Comment: 12 pages; v2: minor corrections, note and references added;
Contribution to proceedings of the 2nd School on "Quantum Gravity and Quantum
Geometry" session of the 9th Hellenic School on Elementary Particle Physics
and Gravity, Corfu, Greece, September 13-20 2009. To be published in General
Relativity and Gravitatio
A New Noncommutative Product on the Fuzzy Two-Sphere Corresponding to the Unitary Representation of SU(2) and the Seiberg-Witten Map
We obtain a new explicit expression for the noncommutative (star) product on
the fuzzy two-sphere which yields a unitary representation. This is done by
constructing a star product, , for an arbitrary representation
of SU(2) which depends on a continuous parameter and searching for
the values of which give unitary representations. We will find two
series of values: and
, where j is the spin of the representation
of SU(2). At the new star product
has poles. To avoid the singularity the functions on the sphere must be
spherical harmonics of order and then reduces
to the star product obtained by Preusnajder. The star product at
, to be denoted by , is new. In this case the
functions on the fuzzy sphere do not need to be spherical harmonics of order
. Because in this case there is no cutoff on the order of
spherical harmonics, the degrees of freedom of the gauge fields on the fuzzy
sphere coincide with those on the commutative sphere. Therefore, although the
field theory on the fuzzy sphere is a system with finite degrees of freedom, we
can expect the existence of the Seiberg-Witten map between the noncommutative
and commutative descriptions of the gauge theory on the sphere. We will derive
the first few terms of the Seiberg-Witten map for the U(1) gauge theory on the
fuzzy sphere by using power expansion around the commutative point .Comment: 15 pages, typos corrected, references added, a note adde
Construction of wedge-local nets of observables through Longo-Witten endomorphisms. II
In the first part, we have constructed several families of interacting
wedge-local nets of von Neumann algebras. In particular, there has been
discovered a family of models based on the endomorphisms of the U(1)-current
algebra of Longo-Witten.
In this second part, we further investigate endomorphisms and interacting
models. The key ingredient is the free massless fermionic net, which contains
the U(1)-current net as the fixed point subnet with respect to the U(1) gauge
action. Through the restriction to the subnet, we construct a new family of
Longo-Witten endomorphisms on the U(1)-current net and accordingly interacting
wedge-local nets in two-dimensional spacetime. The U(1)-current net admits the
structure of particle numbers and the S-matrices of the models constructed here
do mix the spaces with different particle numbers of the bosonic Fock space.Comment: 33 pages, 1 tikz figure. The final version is available under Open
Access. CC-B
The One-loop UV Divergent Structure of U(1) Yang-Mills Theory on Noncommutative R^4
We show that U(1) Yang-Mills theory on noncommutative R^4 can be renormalized
at the one-loop level by multiplicative dimensional renormalization of the
coupling constant and fields of the theory. We compute the beta function of the
theory and conclude that the theory is asymptotically free. We also show that
the Weyl-Moyal matrix defining the deformed product over the space of functions
on R^4 is not renormalized at the one-loop level.Comment: 8 pages. A missing complex "i" is included in the field strength and
the divergent contributions corrected accordingly. As a result the model
turns out to be asymptotically fre
Vacuum configurations for renormalizable non-commutative scalar models
In this paper we find non-trivial vacuum states for the renormalizable
non-commutative model. An associated linear sigma model is then
considered. We further investigate the corresponding spontaneous symmetry
breaking.Comment: 17 page
Evaluation of the Beam Background Contribution to the pp Minimum Bias Sample Used for First Physics
The note describes the beam background conditions during first physics data taking with ALICE and the strategy for the evaluation of the LHC beam background contribution to the minimum bias event sample used for first physics
A Variational Level Set Approach for Surface Area Minimization of Triply Periodic Surfaces
In this paper, we study triply periodic surfaces with minimal surface area
under a constraint in the volume fraction of the regions (phases) that the
surface separates. Using a variational level set method formulation, we present
a theoretical characterization of and a numerical algorithm for computing these
surfaces. We use our theoretical and computational formulation to study the
optimality of the Schwartz P, Schwartz D, and Schoen G surfaces when the volume
fractions of the two phases are equal and explore the properties of optimal
structures when the volume fractions of the two phases not equal. Due to the
computational cost of the fully, three-dimensional shape optimization problem,
we implement our numerical simulations using a parallel level set method
software package.Comment: 28 pages, 16 figures, 3 table
The Equivalence Theorem and Effective Lagrangians
We point out that the equivalence theorem, which relates the amplitude for a
process with external longitudinally polarized vector bosons to the amplitude
in which the longitudinal vector bosons are replaced by the corresponding
pseudo-Goldstone bosons, is not valid for effective Lagrangians. However, a
more general formulation of this theorem also holds for effective interactions.
The generalized theorem can be utilized to determine the high-energy behaviour
of scattering processes just by power counting and to simplify the calculation
of the corresponding amplitudes. We apply this method to the phenomenologically
most interesting terms describing effective interactions of the electroweak
vector and Higgs bosons in order to examine their effects on vector-boson
scattering and on vector-boson-pair production in annihilation. The
use of the equivalence theorem in the literature is examined.Comment: 20 pages LaTeX, BI-TP 94/1
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