1,029 research outputs found
Anyons and the Bose-Fermi duality in the finite-temperature Thirring model
Solutions to the Thirring model are constructed in the framework of algebraic
QFT. It is shown that for all positive temperatures there are fermionic
solutions only if the coupling constant is . These fermions are inequivalent and only for they are canonical
fields. In the general case solutions are anyons. Different anyons (which are
uncountably many) live in orthogonal spaces and obey dynamical equations (of
the type of Heisenberg's "Urgleichung") characterized by the corresponding
values of the statistic parameter. Thus statistic parameter turns out to be
related to the coupling constant and the whole Hilbert space becomes
non-separable with a different "Urgleichung" satisfied in each of its sectors.
This feature certainly cannot be seen by any power expansion in .
Moreover, since the latter is tied to the statistic parameter, it is clear that
such an expansion is doomed to failure and will never reveal the true structure
of the theory.
The correlation functions in the temperature state for the canonical dressed
fermions are shown by us to coincide with the ones for bare fields, that is in
agreement with the uniqueness of the -KMS state over the CAR algebra
( being the shift automorphism). Also the -anyon two-point
function is evaluated and for scalar field it reproduces the result that is
known from the literature.Comment: 25 pages, LaTe
Monopole Vacuum in Non-Abelian Theories
It is shown that, in the theory of interacting Yang -Mills fields and a Higgs
field, there is a topological degeneracy of Bogomol'nyi-Prasad-Sommerfield
(BPS) monopoles and that there arises, in this case, a chromoelectric monopole
characterized by a new topological variable that describes transitions between
topological states of the monopole in the Minkowski space (in just the same way
as an instanton describes such transitions in the Euclidean space). The limit
of an infinitely large mass of the Higgs field at a finite density of the BPS
monopole is considered as a model of the stable vacuum in the pure Yang-Mills
theory. It is shown that, in QCD, such a monopole vacuum may lead to a rising
potential, a topological confinement and an additional mass of the
meson. The relationship between the result obtained here for the generating
functional of perturbation theory and Faddeev-Popov integral is discussed
Meson Production in p+d Reactions
The production of neutral and charged pions as well as eta mesons is studied
in the Delta and N* resonance region, respectively. Heavy A=3 recoils were
measured with the GEM detector. The differential cross sections covering the
full angular range are compared with model calculations.Comment: 4 pages, latex, 4 figures, talk presented at the XVIIth European
Conference on Few-Body Problems in Physics, Evora, Portugal, September 2000;
to be published in Nucl. Phys.
Measurement of p + d -> 3He + eta in S(11) Resonance
We have measured the reaction p + d -> 3He + eta at a proton beam energy of
980 MeV, which is 88.5 MeV above threshold using the new ``germanium wall''
detector system. A missing--mass resolution of the detector system of 2.6% was
achieved. The angular distribution of the meson is forward peaked. We found a
total cross section of (573 +- 83(stat.) +- 69(syst.))nb. The excitation
function for the present reaction is described by a Breit Wigner form with
parameters from photoproduction.Comment: 8 pages, 2 figures, corrected typos in heade
Morphological characteristics of motor neurons do not determine their relative susceptibility to degeneration in a mouse model of severe spinal muscular atrophy
Spinal muscular atrophy (SMA) is a leading genetic cause of infant mortality, resulting primarily from the degeneration and loss of lower motor neurons. Studies using mouse models of SMA have revealed widespread heterogeneity in the susceptibility of individual motor neurons to neurodegeneration, but the underlying reasons remain unclear. Data from related motor neuron diseases, such as amyotrophic lateral sclerosis (ALS), suggest that morphological properties of motor neurons may regulate susceptibility: in ALS larger motor units innervating fast-twitch muscles degenerate first. We therefore set out to determine whether intrinsic morphological characteristics of motor neurons influenced their relative vulnerability to SMA. Motor neuron vulnerability was mapped across 10 muscle groups in SMA mice. Neither the position of the muscle in the body, nor the fibre type of the muscle innervated, influenced susceptibility. Morphological properties of vulnerable and disease-resistant motor neurons were then determined from single motor units reconstructed in Thy.1-YFP-H mice. None of the parameters we investigated in healthy young adult mice - including motor unit size, motor unit arbor length, branching patterns, motor endplate size, developmental pruning and numbers of terminal Schwann cells at neuromuscular junctions - correlated with vulnerability. We conclude that morphological characteristics of motor neurons are not a major determinant of disease-susceptibility in SMA, in stark contrast to related forms of motor neuron disease such as ALS. This suggests that subtle molecular differences between motor neurons, or extrinsic factors arising from other cell types, are more likely to determine relative susceptibility in SMA
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