15,387 research outputs found
No radiative generation of Chern-Simons-like term in Lorentz-violating QED: dealing with IR divergences
The issue intensively claimed in the literature on the generation of a
CPT-odd and Lorentz violating Chern-Simons-like term by radiative corrections
owing to a CPT violating interaction -- the axial coupling of fermions with a
constant vector field b_\m -- is mistaken. The presence of massless gauge
field triggers IR divergences that might show up from the UV subtractions,
therefore, so as to deal with the (actual physical) IR divergences, the
Lowenstein-Zimmermann subtraction scheme, in the framework of BPHZL
renormalization method, has to be adopted. The proof on the non generation of
such a Chern-Simons-like term is done, independent of any kind of
regularization scheme, at all orders in perturbation theory.Comment: In honor of Prof. Manfred Schweda (1939-2017). Work presented at the
XXXVIII National Meeting on Particle Physics and Fields, September 18-22,
2017 - Passa Quatro - Minas Gerais - Brazil. Reference [46] correcte
Tracing the magnetic field morphology of the Lupus I molecular cloud
Deep R-band CCD linear polarimetry collected for fields with lines-of-sight
toward the Lupus I molecular cloud is used to investigate the properties of the
magnetic field within this molecular cloud. The observed sample contains about
7000 stars, almost 2000 of them with polarization signal-to-noise ratio larger
than 5. These data cover almost the entire main molecular cloud and also sample
two diffuse infrared patches in the neighborhood of Lupus I. The large scale
pattern of the plane-of-sky projection of the magnetic field is perpendicular
to the main axis of Lupus I, but parallel to the two diffuse infrared patches.
A detailed analysis of our polarization data combined with the Herschel/SPIRE
350 um dust emission map shows that the principal filament of Lupus I is
constituted by three main clumps acted by magnetic fields having different
large-scale structure properties. These differences may be the reason for the
observed distribution of pre- and protostellar objects along the molecular
cloud and its apparent evolutive stage. On the other hand, assuming that the
magnetic field is composed by a large-scale and a turbulent components, we find
that the latter is rather similar in all three clumps. The estimated
plane-of-sky component of the large-scale magnetic field ranges from about 70
uG to 200 uG in these clumps. The intensity increases towards the Galactic
plane. The mass-to-magnetic flux ratio is much smaller than unity, implying
that Lupus I is magnetically supported on large scales.Comment: 10 pages, 9 figures. Accepted for publication in Ap
An algebraic proof on the finiteness of Yang-Mills-Chern-Simons theory in D=3
A rigorous algebraic proof of the full finiteness in all orders of
perturbation theory is given for the Yang-Mills-Chern-Simons theory in a
general three-dimensional Riemannian manifold. We show the validity of a trace
identity, playing the role of a local form of the Callan-Symanzik equation, in
all loop orders, which yields the vanishing of the beta-functions associated to
the topological mass and gauge coupling constant as well as the anomalous
dimensions of the fields.Comment: 5 pages, revte
Algebraic Renormalization of Parity-Preserving QED_3 Coupled to Scalar Matter II: Broken Case
In this letter the algebraic renormalization method, which is independent of
any kind of regularization scheme, is presented for the parity-preserving QED_3
coupled to scalar matter in the broken regime, where the scalar assumes a
finite vacuum expectation value, . The model shows to be stable
under radiative corrections and anomaly free.Comment: 9 pages, latex, no figure
Geometry of unsteady fluid transport during fluid–structure interactions
We describe the application of tools from dynamical systems to define and quantify the unsteady fluid transport that occurs during fluid–structure interactions and in unsteady recirculating flows. The properties of Lagrangian coherent structures (LCS) are used to enable analysis of flows with arbitrary time-dependence, thereby extending previous analytical results for steady and time-periodic flows. The LCS kinematics are used to formulate a unique, physically motivated definition for fluid exchange surfaces and transport lobes in the flow. The methods are applied to numerical simulations of two-dimensional flow past a circular cylinder at a Reynolds number of 200; and to measurements of a freely swimming organism, the Aurelia aurita jellyfish. The former flow provides a canonical system in which to compare the present geometrical analysis with classical, Eulerian (e.g. vortex shedding) perspectives of fluid–structure interactions. The latter flow is used to deduce the physical coupling that exists between mass and momentum transport during self-propulsion. In both cases, the present methods reveal a well-defined, unsteady recirculation zone that is not apparent in the corresponding velocity or vorticity fields. Transport rates between the ambient flow and the recirculation zone are computed for both flows. Comparison of fluid transport geometry for the cylinder crossflow and the self-propelled swimmer within the context of existing theory for two-dimensional lobe dynamics enables qualitative localization of flow three-dimensionality based on the planar measurements. Benefits and limitations of the implemented methods are discussed, and some potential applications for flow control, unsteady propulsion, and biological fluid dynamics are proposed
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