19,201 research outputs found
Lorentz symmetry breaking in the noncommutative Wess-Zumino model: One loop corrections
In this paper we deal with the issue of Lorentz symmetry breaking in quantum
field theories formulated in a non-commutative space-time. We show that, unlike
in some recente analysis of quantum gravity effects, supersymmetry does not
protect the theory from the large Lorentz violating effects arising from the
loop corrections. We take advantage of the non-commutative Wess-Zumino model to
illustrate this point.Comment: 9 pages, revtex4. Corrected references. Version published in PR
Experimental Observation of Coherence and Stochastic Resonances in an Electronic Chua Circuit
Stochastic and coherence resonances appear in nonlinear systems subjected to
an external source of noise and are characterized by a maximum response at the
optimal value of the noise intensity. This paper shows experimentally that it
is possible to observe them in a chaotic system. To this end we have analysed
an electronic Chua circuit running in the chaotic regime and added noise to its
dynamics. In the case of coherence resonance, we observe an optimal periodicity
for the jumps between chaotic attractors, whereas in the case of stochastic
resonance we observe a maximum in the signal-to-noise ratio at the frequency of
an external sinusoidal perturbation.Comment: 6 page
Flora das Culturas Agrícolas da Ilha de Santiago (cabo Verde)
Com o objectivo de caracterizar as comunidades vegetais que acompanham as culturas
agrícolas de sequeiro e de regadio praticadas em Santiago e, particularmente, no vale da ribeira
Seca, efectuaram-se 16 levantamentos titoecológicos ao longo deste curso de água e encostas
sobranceiras. A inventaria@0 floristica revelou a presenta de 118 taro pertencenteas 3 3 familias.
Analisaram-sea, inda,6 2 levantamentorse alizadose m diversosp ontosd a ilha, tendo sido
identificados1 72t axa pertencenteas 42 familiasG. ramineae. Leguminosae e Compositue sao as
famílias melhor representadasA. flora inventariadaC comparadac om a referida em trabalhos
precedentesr,e alizadosp or outrosa utores,r evelandolao correnciad e, pelo menos,1 82t axa na
flora infestante.
Os levantamentos da ribeira Seca foram analisadosa travt5sd o programad e análise
numérica TWINSPAN, que indicou a presentad e 4 agrupamentosv egetais distintos, cuja
interpretacao,a tendendoà s característicase dáticas,c limáticase topográticasd os locais onde
ocorrem,s ugeriua disponibilidadeh idrica comoo factorm aisd eterminantde as uac omposicáo.
Palavras-chavefl:o ra, adventiciasd asc ulturasT, WINSPAN, ilhasd eC aboV erde, Santiago.
In order to identify and to characterizeth e plant communitiesp resenat t the irrigated and
dry cropso f ribeira Secav alley, it were established16 s amplep lots. The tloristic inventory has revealedt he presenteo f 118 tara belongingt o 33 families.I n addition,m ore 62 samplep lots,were establishedth roughoutt he island,w hich permittedt he identifkation of 172t ara from 42 families.G ramineae, CompQsitae &ndL eguminosae weret he mostr epresentativeosn es.T his flora
is comparedw ith that referred in precedingw orksf rom othersa uthors,r evealingt he occurrence
of, at least, 182 tma in the weed flora.
The application of the TWINSPAN numerical analysis, to the plots in the ribeira Seca
vallcy. has revealed the presente of 4 distinct plant communities, which were related with
edaphic,c limatic and topographicf actors.T his analysiss uggestetdh at the water availability wa.s the mainf actor affecting the speciesc ompositionof the communities.
Key-words:f lora weedsT, WINSPAN, CapeV erdei slandsS, antiago
Second Generation of 'Miranda Procedure' for CP Violation in Dalitz Studies of B (\& D \& \tau) Decays
The `Miranda Procedure' proposed for analyzing Dalitz plots for CP
asymmetries in charged B and D decays in a model-independent manner is extended
and refined. The complexity of CKM CP phenomenology through order
is needed in searches for New Dynamics (ND). Detailed analyses of three-body
final states other great advantages: (i) They give us more powerful tools for
deciding whether an observed CP asymmetry rep- resents the manifestation of ND
and its features. (ii) Many advantages can already be obtained by the `Miranda
Procedure' without construction of a detailed Dalitz plot de- scription. (iii)
One studies CP asymmetries independent of production asymmetries. We illustrate
the power of a second generation Miranda Procedure with examples with time
integrated rates for decays to final states as
trial runs with comments on .Comment: 29 pages, 7 figure
Type-II super-Backlund transformation and integrable defects for the N=1 super sinh-Gordon model
A new super-Backlund transformation for the N=1 supersymmetric sinh-Gordon
equation is constructed. Based on this construction we propose a type-II
integrable defect for the supersymmetric sinh-Gordon model consistent with this
new transformation through the Lagrangian formalism. Explicit expressions for
the modified conserved energy, momentum and supercharges are also computed. In
addition, we show for the model that the type-II defect can also been regarded
as a pair of fused defects of a previously introduced type. The explicit
derivation of the associated defect matrices is also presented as a necessary
condition for the integrability of the model.Comment: Latex 31 pages. Version accepted for publicatio
The Noncommutative Supersymmetric Nonlinear Sigma Model
We show that the noncommutativity of space-time destroys the
renormalizability of the 1/N expansion of the O(N) Gross-Neveu model. A similar
statement holds for the noncommutative nonlinear sigma model. However, we show
that, up to the subleading order in 1/N expansion, the noncommutative
supersymmetric O(N) nonlinear sigma model becomes renormalizable in D=3. We
also show that dynamical mass generation is restored and there is no
catastrophic UV/IR mixing. Unlike the commutative case, we find that the
Lagrange multiplier fields, which enforce the supersymmetric constraints, are
also renormalized. For D=2 the divergence of the four point function of the
basic scalar field, which in D=3 is absent, cannot be eliminated by means of a
counterterm having the structure of a Moyal product.Comment: 15 pages, 7 figures, revtex, minor modifications in the text,
references adde
Dressing approach to the nonvanishing boundary value problem for the AKNS hierarchy
We propose an approach to the nonvanishing boundary value problem for
integrable hierarchies based on the dressing method. Then we apply the method
to the AKNS hierarchy. The solutions are found by introducing appropriate
vertex operators that takes into account the boundary conditions.Comment: Published version Proc. Quantum Theory and Symmetries 7
(QTS7)(Prague, Czech Republic, 2011
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