8,983 research outputs found
High energy improved scalar quantum field theory from noncommutative geometry without UV/IR-mixing
We consider an interacting scalar quantum field theory on noncommutative
Euclidean space. We implement a family of noncommutative deformations, which --
in contrast to the well known Moyal-Weyl deformation -- lead to a theory with
modified kinetic term, while all local potentials are unaffected by the
deformation. We show that our models, in particular, include propagators with
anisotropic scaling z=2 in the ultraviolet (UV). For a \Phi^4-theory on our
noncommutative space we obtain an improved UV behaviour at the one-loop level
and the absence of UV/IR-mixing and of the Landau pole.Comment: 4 pages, no figures, elsarticle.cls; references adde
Proton-Proton Physics with ALICE
The goal of the ALICE experiment at LHC is to study strongly interacting
matter at high energy densities as well as the signatures and properties of the
quark-gluon plasma. This goal manifests itself in a rich physics program.
Although ALICE will mainly study heavy-ion collisions, a dedicated program will
concentrate on proton-proton physics. The first part will introduce the ALICE
experiment from a pp measurement's point of view. Two unique properties are its
low pT cut-off and the excellent PID capabilities. The various topics of the
proton-proton physics program, which will allow a close scrutiny of existing
theoretical models, will be described. Furthermore, the interpretation of
measurements of heavy-ion collisions necessitates the comparison to
measurements of pp collisions. The second part will concentrate on the day-1
physics program of ALICE. At startup, neither the LHC luminosity nor its energy
will have their nominal values. Furthermore, the ALICE detector is in the
process of being aligned and calibrated. Still several physics topics can be
studied from the very beginning. These will be presented as well as the effort
that is already ongoing to be ready for the first collision. The statistics
needed for each of the topics will be given with respect to the foreseen LHC
startup scenario.Comment: Contribution for the 1st International Workshop on Soft Physics in
ultrarelativistic Heavy Ion Collisions, Catania, Italy, 200
Witten index, axial anomaly, and Krein's spectral shift function in supersymmetric quantum mechanics
A new method is presented to study supersymmetric quantum mechanics. Using relative scattering techniques, basic relations are derived between Kreinâs spectral shift function, the Witten index, and the anomaly. The topological invariance of the spectral shift function is discussed. The power of this method is illustrated by treating various models and calculating explicitly the spectral shift function, the Witten index, and the anomaly. In particular, a complete treatment of the twoâdimensional magnetic field problem is given, without assuming that the magnetic flux is quantized
Regularization of 2d supersymmetric Yang-Mills theory via non commutative geometry
The non commutative geometry is a possible framework to regularize Quantum
Field Theory in a nonperturbative way. This idea is an extension of the lattice
approximation by non commutativity that allows to preserve symmetries. The
supersymmetric version is also studied and more precisely in the case of the
Schwinger model on supersphere [14]. This paper is a generalization of this
latter work to more general gauge groups
Generalized local interactions in 1D: solutions of quantum many-body systems describing distinguishable particles
As is well-known, there exists a four parameter family of local interactions
in 1D. We interpret these parameters as coupling constants of delta-type
interactions which include different kinds of momentum dependent terms, and we
determine all cases leading to many-body systems of distinguishable particles
which are exactly solvable by the coordinate Bethe Ansatz. We find two such
families of systems, one with two independent coupling constants deforming the
well-known delta interaction model to non-identical particles, and the other
with a particular one-parameter combination of the delta- and (so-called)
delta-prime interaction. We also find that the model of non-identical particles
gives rise to a somewhat unusual solution of the Yang-Baxter relations. For the
other model we write down explicit formulas for all eigenfunctions.Comment: 23 pages v2: references adde
Degenerate noncommutativity
We study a renormalizable four dimensional model with two deformed quantized
space directions. A one-loop renormalization is performed explicitly. The
Euclidean model is connected to the Minkowski version via an analytic
continuation. At a special value of the parameters a nontrivial fixed point of
the renormalization group occurs.Comment: 16 page
On the Effective Action of Noncommutative Yang-Mills Theory
We compute here the Yang-Mills effective action on Moyal space by integrating
over the scalar fields in a noncommutative scalar field theory with harmonic
term, minimally coupled to an external gauge potential. We also explain the
special regularisation scheme chosen here and give some links to the Schwinger
parametric representation. Finally, we discuss the results obtained: a
noncommutative possibly renormalisable Yang-Mills theory.Comment: 19 pages, 6 figures. At the occasion of the "International Conference
on Noncommutative Geometry and Physics", April 2007, Orsay (France). To
appear in J. Phys. Conf. Se
BaFe_{1.8}Co_{0.2}As_2 thin film hybrid Josephson junctions
Josephson junctions with iron pnictides open the way for fundamental
experiments on superconductivity in these materials and their application in
superconducting devices. Here, we present hybrid Josephson junctions with a
BaFe_{1.8}Co_{0.2}As_2 thin film electrode, an Au barrier and a PbIn counter
electrode. The junctions show RSJ-like current-voltage characteristics up to
the critical temperature of the counter electrode of about 7.2K. The
temperature dependence of the critical current, IC, does not show an
Ambegaokar-Baratoff behavior. Well-pronounced Shapiro steps are observed at
microwave frequencies of 10-18GHz. Assuming an excess current, I_ex, of 200
{\mu}A at 4.2K we get an effective I_C R_N product of 6 {\mu}V.Comment: submitted to Appl. Phys. Let
The rigid syntomic ring spectrum
The aim of this paper is to show that Besser syntomic cohomology is
representable by a rational ring spectrum in the motivic homotopical sense. In
fact, extending previous constructions, we exhibit a simple representability
criterion and we apply it to several cohomologies in order to get our central
result. This theorem gives new results for syntomic cohomology such as
h-descent and the compatibility of cycle classes with Gysin morphisms. Along
the way, we prove that motivic ring spectra induces a complete Bloch-Ogus
cohomological formalism and even more. Finally, following a general motivic
homotopical philosophy, we exhibit a natural notion of syntomic coefficients.Comment: Final version to appear in the Journal de l'institut des
Math\'ematiques de Jussieu. Many typos have been corrected and the exposition
has been improved according to the suggestions of the referees: we thank them
a lot
Measuring photon anti-bunching from continuous variable sideband squeezing
We present a technique for measuring the second-order coherence function
of light using a Hanbury-Brown Twiss intensity interferometer
modified for homodyne detection. The experiment was performed entirely in the
continuous variable regime at the sideband frequency of a bright carrier field.
We used the setup to characterize for thermal and coherent
states, and investigated its immunity to optical loss. We measured
of a displaced squeezed state, and found a best anti-bunching
statistic of .Comment: 4 pages, 4 figure
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