1,356 research outputs found
Michel theory of symmetry breaking and gauge theories
We extend Michel's theorem on the geometry of symmetry breaking [L. Michel,
{\it Comptes Rendus Acad. Sci. Paris} {\bf 272-A} (1971), 433-436] to the case
of pure gauge theories, i.e. of gauge-invariant functionals defined on the
space of connections of a principal fiber bundle. Our proof follows
closely the original one by Michel, using several known results on the geometry
of . The result (and proof) is also extended to the case of gauge
theories with matter fields.Comment: 24 pages. An old paper posted for archival purpose
Quaternionic integrable systems
Standard (Arnold-Liouville) integrable systems are intimately related to
complex rotations. One can define a generalization of these, sharing many of
their properties, where complex rotations are replaced by quaternionic ones.
Actually this extension is not limited to the integrable case: one can define a
generalization of Hamilton dynamics based on hyperKahler structures.Comment: 10 pages. To appear in the proceedings of the SPT2002 conference,
edited by S. Abenda, G. Gaeta and S. Walcher, World Scientifi
Peer gender and STEM specialization
This paper shows that students are less likely to specialize in mathematics when exposed to a high share of male peers. I exploit a curricular reform that incentivized students to obtain a mathematics qualification post-16. I show that, for those students affected by the reform, the higher the share of same-gender classmates, the higher the likelihood of obtaining a mathematics qualification for boys, and the lower the likelihood for girls. I interpret this as suggestive evidence that one’s perceived ability in mathematics, a boy-dominated subject, decreases when the share of male classmates increases. This further affects STEM participation in higher education
A variational principle for volume-preserving dynamics
We provide a variational description of any Liouville (i.e. volume
preserving) autonomous vector fields on a smooth manifold. This is obtained via
a ``maximal degree'' variational principle; critical sections for this are
integral manifolds for the Liouville vector field. We work in coordinates and
provide explicit formulae
Strangeness Production in pp,pA,AA Interactions at SPS Energies.HIJING Approach
In this report we have made a systematic study of strangeness production in
proton-proton(pp),proton-nucleus(pA) and nucleus- nucleus(AA) collisions at
CERN Super Proton Synchroton energies, using \\ (version ). Numerical results for mean
multiplicities of neutral strange particles ,as well as their ratios to
negatives hadrons() for
p-p,nucleon-nucleon(N-N),\,\,p-S,\,\,p-Ag,\,\,p-Au('min. bias')collisions and
p-Au,\,\,S-S,\,\,S-Ag,\,\,S-Au ('central')collisions are compared to
experimental data available from CERN experiments and also with recent
theoretical estimations given by others models. Neutral strange particle
abundances are quite well described for p-p,N-N and p-A interactions ,but are
underpredicted by a factor of two in A-A interactions for
in symmetric collisions(S-S,\,\,Pb-Pb)and for
in asymmetric ones(S-Ag,\,\,S-Au,\,\,S-W). A
qualitative prediction for rapidity, transverse kinetic energy and transverse
momenta normalized distributions are performed at 200 GeV/Nucleon in
p-S,S-S,S-Ag and S-Au collisions in comparison with recent experimental data.
HIJING model predictions for coming experiments at CERN for S-Au, S-W and Pb-Pb
interactions are given. The theoretical calculations are estimated in a full
phase space.Comment: 33 pages(LATEX),18 figures not included,available in hard copy upon
request , Dipartamento di Fisica Padova,report DFPD-94-NP-4
Local and nonlocal solvable structures in ODEs reduction
Solvable structures, likewise solvable algebras of local symmetries, can be
used to integrate scalar ODEs by quadratures. Solvable structures, however, are
particularly suitable for the integration of ODEs with a lack of local
symmetries. In fact, under regularity assumptions, any given ODE always admits
solvable structures even though finding them in general could be a very
difficult task. In practice a noteworthy simplification may come by computing
solvable structures which are adapted to some admitted symmetry algebra. In
this paper we consider solvable structures adapted to local and nonlocal
symmetry algebras of any order (i.e., classical and higher). In particular we
introduce the notion of nonlocal solvable structure
On the geometry of lambda-symmetries, and PDEs reduction
We give a geometrical characterization of -prolongations of vector
fields, and hence of -symmetries of ODEs. This allows an extension to
the case of PDEs and systems of PDEs; in this context the central object is a
horizontal one-form , and we speak of -prolongations of vector fields
and -symmetries of PDEs. We show that these are as good as standard
symmetries in providing symmetry reduction of PDEs and systems, and explicit
invariant solutions
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