53 research outputs found
What Can be Learned Studying the Distribution of the Biggest Fragment ?
In the canonical formalism of statistical physics, a signature of a first
order phase transition for finite systems is the bimodal distribution of an
order parameter. Previous thermodynamical studies of nuclear sources produced
in heavy-ion collisions provide information which support the existence of a
phase transition in those finite nuclear systems. Some results suggest that the
observable Z1 (charge of the biggest fragment) can be considered as a reliable
order parameter of the transition. This talk will show how from peripheral
collisions studied with the INDRA detector at GSI we can obtain this bimodal
behaviour of Z1. Getting rid of the entrance channel effects and under the
constraint of an equiprobable distribution of excitation energy (E*), we use
the canonical description of a phase transition to link this bimodal behaviour
with the residual convexity of the entropy. Theoretical (with and without phase
transition) and experimental Z1-E* correlations are compared. This comparison
allows us to rule out the case without transition. Moreover that quantitative
comparison provides us with information about the coexistence region in the
Z1-E* plane which is in good agreement with that obtained with the signal of
abnormal uctuations of configurational energy (microcanonical negative heat
capacity).Comment: 8 page
Advancement in the understanding of multifragmentation and phase transition for hot nuclei
Recent advancement on the knowledge of multifragmentation and phase
transition for hot nuclei is reported. It concerns i) the influence of radial
collective energy on fragment partitions and the derivation of general
properties of partitions in presence of such a collective energy, ii) a better
knowledge of freeze-out properties obtained by means of a simulation based on
all the available experimental information and iii) the quantitative study of
the bimodal behaviour of the heaviest fragment charge distribution for
fragmenting hot heavy quasi-projectiles which allows, for the first time, to
estimate the latent heat of the phase transition.Comment: 9 pages, Proceedings of IWM09, November 4-7, Catania (Italy
Genetic analysis of emotional reactivity in sheep: effects of the genotypes of the lambs and of their dams
A total of 1347 weaned lambs from eight genotypes were tested over five consecutive years: Romanov (ROM) and Lacaune (LAC) pure breeds, the two F1 crossbreeds (RL and LR) and the offspring of ewes from these four genotypes sired with Berrichon-du-Cher rams (BCF). The lambs were individually exposed to three challenging tests involving novelty, human contact and social isolation. Ten synthetic variables were used to express social reactivity (i.e., active vs. passive strategy), exploratory activity and reactivity to humans. BCF crossbreds were more active (i.e., high bleats, locomotion and attempts to escape) than purebreds and F1. In contrast, ROM expressed more passive responses (i.e., low bleats and vigilance postures) than LAC and BCF crossbreds. In addition, ROM approached a motionless human less and had longer flight distances to an approaching human than did LAC and BCF crossbreds. When restrained, ROM, and to a lesser extent B×ROM and B×LR, avoided human contact more than did LAC, RL and B×LAC. Most of these differences were explained by direct additive genetic effects while maternal influences or heterosis effects were rarely significant. The highest heritability was for high bleats (h2 = 0.48). Females were more active and avoided human contact more than did males
Master singular behavior from correlation length measurements for seven one-component fluids near their gas-liquid critical point
We present the master (i.e. unique) behavior of the correlation length, as a
function of the thermal field along the critical isochore, asymptotically close
to the gas-liquid critical point of xenon, krypton, argon, helium 3, sulfur
hexafluoride, carbon dioxide and heavy water. It is remarkable that this
unicity extends to the correction-to-scaling terms. The critical parameter set
which contains all the needed information to reveal the master behavior, is
composed of four thermodynamic coordinates of the critical point and one
adjustable parameter which accounts for quantum effects in the helium 3 case.
We use a scale dilatation method applied to the relevant physical variables of
the onecomponent fluid subclass, in analogy with the basic hypothesis of the
renormalization theory. This master behavior for the correlation length
satisfies hyperscaling. We finally estimate the thermal field extent, where the
critical crossover of the singular thermodynamic and correlation functions
deviate from the theoretical crossover function obtained from field theory.Comment: Submitted to Physical Review
Constrained caloric curves and phase transition for hot nuclei
Simulations based on experimental data obtained from multifragmenting
quasi-fused nuclei produced in central Xe + Sn collisions have
been used to deduce event by event freeze-out properties in the thermal
excitation energy range 4-12 AMeV [Nucl. Phys. A809 (2008) 111]. From these
properties and the temperatures deduced from proton transverse momentum
fluctuations, constrained caloric curves have been built. At constant average
volumes caloric curves exhibit a monotonic behaviour whereas for constrained
pressures a backbending is observed. Such results support the existence of a
first order phase transition for hot nuclei.Comment: 14 pages, 5 figures, accepted in Physics Letters
The prominent role of the heaviest fragment in multifragmentation and phase transition for hot nuclei
The role played by the heaviest fragment in partitions of multifragmenting
hot nuclei is emphasized. Its size/charge distribution (mean value,
fluctuations and shape) gives information on properties of fragmenting nuclei
and on the associated phase transition.Comment: 11 pages, Proceedings of IWND09, August 23-25, Shanghai (China
Master crossover functions for the one-component fluid "subclass"
Introducing three well-defined dimensionless numbers, we establish the link
between the scale dilatation method able to estimate master (i.e. unique)
singular behaviors of the one-component fluid "subclass" and the universal
crossover functions recently estimated [Garrabos and Bervillier, Phys. Rev. E
74, 021113 (2006)] from the bounded results of the massive renormalization
scheme applied to the..
Master crossover behavior of parachor correlations for one-component fluids
The master asymptotic behavior of the usual parachor correlations, expressing
surface tension as a power law of the density difference
between coexisting liquid and vapor, is analyzed for a
series of pure compounds close to their liquid-vapor critical point, using only
four critical parameters , , and ,
for each fluid.
... The main consequences of these theoretical estimations are discussed in
the light of engineering applications and process simulations where parachor
correlations constitute one of the most practical method for estimating surface
tension from density and capillary rise measurements
Multifragmentation and phase transition for hot nuclei
5 pages, Proceedings of NN2009, August 17-21, Beijing (China)Recent important progress on the knowledge of multifragmentation and phase transition for hot nuclei, thanks to the high detection quality of the INDRA array, is reported. It concerns i) the radial collective energies involved in hot fragmenting nuclei/sources produced in central and semi- peripheral collisions and their influence on the observed fragment partitions, ii) a better knowledge of freeze-out properties obtained by means of a simulation based on all the available experimental information and iii) the quantitative study of the bimodal behaviour of the heaviest fragment distribution for fragmenting hot heavy quasi-projectiles which allows the extraction, for the first time, of an estimate of the latent heat of the phase transition
Master singular behavior for the Sugden factor of the one-component fluids near their gas-liquid critical point
We present the master (i.e. unique) behavior of the squared capillary length
- so called the Sudgen factor-, as a function of the temperature-like field
along the critical isochore, asymptotically close to the gas-liquid critical
point of twenty (one component) fluids. This master behavior is obtained using
the scale dilatation of the relevant physical fields of the one-component
fluids. The scale dilatation introduces the fluid-dependent scale factors in a
manner analog with the linear relations between physical fields and scaling
fields needed by the renormalization theory applied to the Ising-like
universality class. The master behavior for the Sudgen factor satisfies
hyperscaling and can be asymptotically fitted by the leading terms of the
theoretical crossover functions for the correlation length and the
susceptibility in the homogeneous domain recently obtained from massive
renormalization in field theory. In the absence of corresponding estimation of
the theoretical crossover functions for the interfacial tension, we define the
range of the temperature-like field where the master leading power law can be
practically used to predict the singular behavior of the Sudgen factor in
conformity with the theoretical description provided by the massive
renormalization scheme within the extended asymptotic domain of the
one-component fluid "subclass"
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