558 research outputs found

### Cognitive adaptation in asexual and sexual wasps living in contrasted environments.

Differences in learning and memory dynamics between populations are suspected to result from differences in ecological constraints such as resource distribution. The two reproductive modes (strains) of the parasitoid wasp Venturia canescens share the same geographical areas but live in contrasting habitats: arrhenotokous wasps live in the wild (generally orchards), whereas thelytokous ones live mostly in stored-products buildings (e.g. granaries). This species thus represents a relevant biological model for understanding the relationship between the ecological constraints faced by a species and its memory and learning ability. We showed that after having laid eggs in presence of both a synthetic odour and natural olfactory cues of their host, arrhenotokous wasps exhibited a change in their behavioural response towards the synthetic odour that was at least as pronounced as in thelytokous ones even though they were faster in their decision-making process. This is consistent with better learning skills in arrhenotokous wasps. The corresponding memory trace persisted in both strains for at least 51 h. We compare and discuss the learning and memory ablities of both strains as a function of their costs and benefits in their preferential habitats

### The Elusive p-air Cross Section

For the \pbar p and $pp$ systems, we have used all of the extensive data of
the Particle Data Group[K. Hagiwara {\em et al.} (Particle Data Group), Phys.
Rev. D 66, 010001 (2002).]. We then subject these data to a screening process,
the ``Sieve'' algorithm[M. M. Block, physics/0506010.], in order to eliminate
``outliers'' that can skew a $\chi^2$ fit. With the ``Sieve'' algorithm, a
robust fit using a Lorentzian distribution is first made to all of the data to
sieve out abnormally high \delchi, the individual i$^{\rm th}$ point's
contribution to the total $\chi^2$. The $\chi^2$ fits are then made to the
sieved data. We demonstrate that we cleanly discriminate between asymptotic
$\ln s$ and $\ln^2s$ behavior of total hadronic cross sections when we require
that these amplitudes {\em also} describe, on average, low energy data
dominated by resonances. We simultaneously fit real analytic amplitudes to the
``sieved'' high energy measurements of $\bar p p$ and $pp$ total cross sections
and $\rho$-values for $\sqrt s\ge 6$ GeV, while requiring that their asymptotic
fits smoothly join the the $\sigma_{\bar p p}$ and $\sigma_{pp}$ total cross
sections at $\sqrt s=$4.0 GeV--again {\em both} in magnitude and slope. Our
results strongly favor a high energy $\ln^2s$ fit, basically excluding a $\ln
s$ fit. Finally, we make a screened Glauber fit for the p-air cross section,
using as input our precisely-determined $pp$ cross sections at cosmic ray
energies.Comment: 15 pages, 6 figures, 2 table,Paper delivered at c2cr2005 Conference,
Prague, September 7-13, 2005. Fig. 2 was missing from V1. V3 fixes all
figure

### What do experimental data "say" about growth of hadronic total cross-section?

We reanalyse $\bar p p$ and $pp$ high energy data of the elastic scattering
above $\sqrt{s}=5$ GeV on the total cross-section $\sigma_{tot}$ and on the
forward $\rho$-ratio for various models of Pomeron, utilizing two methods. The
first one is based on analytic amplitudes, the other one relies on assumptions
for $\sigma_{tot}$ and on dispersion relation for $\rho$. We argue that it is
not possible, from fitting only existing data for forward scattering, to select
a definite asymptotic growth with the energy of $\sigma_{tot}$. We find
equivalent fits to the data together with a logarithmic Pomeron giving a
behavior $\sigma_{tot} \propto \ln ^\gamma s$, $\gamma\in [0.5,2.20]$ and with
a supercritical Pomeron giving a behavior $\sigma_{tot} \propto s^\epsilon$,
$\epsilon\in [0.01,0.10]$.Comment: LaTeX, 18 pages, 5 eps figures included, to be published in Il Nuovo
Ciment

### Lattice approach to high-energy hadron-hadron scattering

We discuss the non perturbative approach to the problem of high-energy
hadron-hadron (dipole-dipole) scattering at low momentum transfer by means of
numerical simulations in Lattice Gauge Theory.Comment: 4 pages, 5 figures, LaTeX with espcrc2.sty (v. 2.7). To appear in the
proceedings of the 14th International QCD Conference (QCD 08), Montpellier,
France, 7-12 July 200

### Phenomenology of pp->pp eta reaction close to threshold

The recent high statistics measurement of the pp -> pp eta reaction at an
excess energy Q=15.5 MeV has been analysed by means of partial wave
decomposition of the cross section. Guided by the dominance of the final state
1S0 pp interaction (FSI), we keep only terms involving the FSI enhancement
factor. The measured p-p and p-eta effective mass spectra can be well
reproduced by lifting the standard on-shell approximation in the enhancement
factor and by allowing for a linear energy dependence in the leading 3P0->1S0,s
partial wave amplitude. Higher partial waves seem to play only a marginal role

### Antilinear deformations of Coxeter groups, an application to Calogero models

We construct complex root spaces remaining invariant under antilinear
involutions related to all Coxeter groups. We provide two alternative
constructions: One is based on deformations of factors of the Coxeter element
and the other based on the deformation of the longest element of the Coxeter
group. Motivated by the fact that non-Hermitian Hamiltonians admitting an
antilinear symmetry may be used to define consistent quantum mechanical systems
with real discrete energy spectra, we subsequently employ our constructions to
formulate deformations of Coxeter models remaining invariant under these
extended Coxeter groups. We provide explicit and generic solutions for the
Schroedinger equation of these models for the eigenenergies and corresponding
wavefunctions. A new feature of these novel models is that when compared with
the undeformed case their solutions are usually no longer singular for an
exchange of an amount of particles less than the dimension of the
representation space of the roots. The simultaneous scattering of all particles
in the model leads to anyonic exchange factors for processes which have no
analogue in the undeformed case.Comment: 32 page

### Strings from position-dependent noncommutativity

We introduce a new set of noncommutative space-time commutation relations in
two space dimensions. The space-space commutation relations are deformations of
the standard flat noncommutative space-time relations taken here to have
position dependent structure constants. Some of the new variables are
non-Hermitian in the most natural choice. We construct their Hermitian
counterparts by means of a Dyson map, which also serves to introduce a new
metric operator. We propose PTlike symmetries, i.e.antilinear involutory maps,
respected by these deformations. We compute minimal lengths and momenta arising
in this space from generalized versions of Heisenberg's uncertainty relations
and find that any object in this two dimensional space is string like,
i.e.having a fundamental length in one direction beyond which a resolution is
impossible. Subsequently we formulate and partly solve some simple models in
these new variables, the free particle, its PT-symmetric deformations and the
harmonic oscillator.Comment: 11 pages, Late

### A non self-adjoint model on a two dimensional noncommutative space with unbound metric

We demonstrate that a non-self-adjoint Hamiltonian of harmonic-oscillator type defined on a two-dimensional noncommutative space can be diagonalized exactly by making use of pseudobosonic operators. The model admits an antilinear symmetry and is of the type studied in the context of PT-symmetric quantum mechanics. Its eigenvalues are computed to be real for the entire range of the coupling constants and the biorthogonal sets of eigenstates for the Hamiltonian and its adjoint are explicitly constructed. We show that despite the fact that these sets are complete and biorthogonal, they involve an unbounded metric operator and therefore do not constitute (Riesz) bases for the Hilbert space L2(R2), but instead only D quasibases. As recently proved by one of us, this is sufficient to deduce several interesting consequences

### Elastic pp Scattering at LHC Energies

We consider the first LHC data for elastic pp scattering in the framework of
Regge theory with multiple Pomeron exchanges. The simplest eikonal approach
allows one to describe differential elastic cross sections at LHC, as well as
pp and $\bar{p}p$ scattering at lower collider energies, on a reasonable level.Comment: 11 pages, 5 figures, and 1 tabl

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