204 research outputs found
SM(2,4k) fermionic characters and restricted jagged partitions
A derivation of the basis of states for the superconformal minimal
models is presented. It relies on a general hypothesis concerning the role of
the null field of dimension . The basis is expressed solely in terms of
modes and it takes the form of simple exclusion conditions (being thus a
quasi-particle-type basis). Its elements are in correspondence with
-restricted jagged partitions. The generating functions of the latter
provide novel fermionic forms for the characters of the irreducible
representations in both Ramond and Neveu-Schwarz sectors.Comment: 12 page
New path description for the M(k+1,2k+3) models and the dual Z_k graded parafermions
We present a new path description for the states of the non-unitary
M(k+1,2k+3) models. This description differs from the one induced by the
Forrester-Baxter solution, in terms of configuration sums, of their
restricted-solid-on-solid model. The proposed path representation is actually
very similar to the one underlying the unitary minimal models M(k+1,k+2), with
an analogous Fermi-gas interpretation. This interpretation leads to fermionic
expressions for the finitized M(k+1,2k+3) characters, whose infinite-length
limit represent new fermionic characters for the irreducible modules. The
M(k+1,2k+3) models are also shown to be related to the Z_k graded parafermions
via a (q to 1/q) duality transformation.Comment: 43 pages (minor typo corrected and minor rewording in the
introduction
Nonlocal operator basis from the path representation of the M(k+1,k+2) and the M(k+1,2k+3) minimal models
We reinterpret a path describing a state in an irreducible module of the
unitary minimal model M(k+1,k+2) in terms of a string of charged operators
acting on the module's ground-state path. Each such operator acts non-locally
on a path. The path characteristics are then translated into a set of
conditions on sequences of operators that provide an operator basis. As an
application, we re-derive the vacuum finite fermionic character by constructing
the generating function of these basis states.
These results generalize directly to the M(k+1,2k+3) models, the close
relatives of the unitary models in terms of path description.Comment: 22 pages, new title and abstract; section 1 rewritten and section 2.2
improved; version to appear in J. Phys.
<i>In vivo</i> microscale measurements of light and photosynthesis during coral bleaching:evidence for the optical feedback loop?
Climate change-related coral bleaching, i.e., the visible loss of zooxanthellae from the coral host, is increasing in frequency and extent and presents a major threat to coral reefs globally. Coral bleaching has been proposed to involve accelerating light stress of their microalgal endosymbionts via a positive feedback loop of photodamage, symbiont expulsion and excess in vivo light exposure. To test this hypothesis, we used light and O(2) microsensors to characterize in vivo light exposure and photosynthesis of Symbiodinium during a thermal stress experiment. We created tissue areas with different densities of Symbiodinium cells in order to understand the optical properties and light microenvironment of corals during bleaching. Our results showed that in bleached Pocillopora damicornis corals, Symbiodinium light exposure was up to fivefold enhanced relative to healthy corals, and the relationship between symbiont loss and light enhancement was well-described by a power-law function. Cell-specific rates of Symbiodinium gross photosynthesis and light respiration were enhanced in bleached P. damicornis compared to healthy corals, while areal rates of net photosynthesis decreased. Symbiodinium light exposure in Favites sp. revealed the presence of low light microniches in bleached coral tissues, suggesting that light scattering in thick coral tissues can enable photoprotection of cryptic symbionts. Our study provides evidence for the acceleration of in vivo light exposure during coral bleaching but this optical feedback mechanism differs between coral hosts. Enhanced photosynthesis in relation to accelerating light exposure shows that coral microscale optics exerts a key role on coral photophysiology and the subsequent degree of radiative stress during coral bleaching
Role of non-linear data processing on speech recognition task in the framework of reservoir computing
The reservoir computing neural network architecture is widely used to test
hardware systems for neuromorphic computing. One of the preferred tasks for
bench-marking such devices is automatic speech recognition. However, this task
requires acoustic transformations from sound waveforms with varying amplitudes
to frequency domain maps that can be seen as feature extraction techniques.
Depending on the conversion method, these may obscure the contribution of the
neuromorphic hardware to the overall speech recognition performance. Here, we
quantify and separate the contributions of the acoustic transformations and the
neuromorphic hardware to the speech recognition success rate. We show that the
non-linearity in the acoustic transformation plays a critical role in feature
extraction. We compute the gain in word success rate provided by a reservoir
computing device compared to the acoustic transformation only, and show that it
is an appropriate benchmark for comparing different hardware. Finally, we
experimentally and numerically quantify the impact of the different acoustic
transformations for neuromorphic hardware based on magnetic nano-oscillators.Comment: 13 pages, 5 figure
Traffic Instabilities in Self-Organized Pedestrian Crowds
In human crowds as well as in many animal societies, local interactions among
individuals often give rise to self-organized collective organizations that
offer functional benefits to the group. For instance, flows of pedestrians
moving in opposite directions spontaneously segregate into lanes of uniform
walking directions. This phenomenon is often referred to as a smart collective
pattern, as it increases the traffic efficiency with no need of external
control. However, the functional benefits of this emergent organization have
never been experimentally measured, and the underlying behavioral mechanisms
are poorly understood. In this work, we have studied this phenomenon under
controlled laboratory conditions. We found that the traffic segregation
exhibits structural instabilities characterized by the alternation of organized
and disorganized states, where the lifetime of well-organized clusters of
pedestrians follow a stretched exponential relaxation process. Further analysis
show that the inter-pedestrian variability of comfortable walking speeds is a
key variable at the origin of the observed traffic perturbations. We show that
the collective benefit of the emerging pattern is maximized when all
pedestrians walk at the average speed of the group. In practice, however, local
interactions between slow- and fast-walking pedestrians trigger global
breakdowns of organization, which reduce the collective and the individual
payoff provided by the traffic segregation. This work is a step ahead toward
the understanding of traffic self-organization in crowds, which turns out to be
modulated by complex behavioral mechanisms that do not always maximize the
group's benefits. The quantitative understanding of crowd behaviors opens the
way for designing bottom-up management strategies bound to promote the
emergence of efficient collective behaviors in crowds.Comment: Article published in PLoS Computational biology. Freely available
here:
http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.100244
TESS asteroseismology of the known red-giant host stars HD 212771 and HD 203949
International audienc
The structure of the Yang-Mills spectrum for arbitrary simple gauge algebras
The mass spectrum of pure Yang-Mills theory in 3+1 dimensions is discussed
for an arbitrary simple gauge algebra within a quasigluon picture. The general
structure of the low-lying gluelump and two-quasigluon glueball spectrum is
shown to be common to all algebras, while the lightest three-quasigluon
glueballs only exist when the gauge algebra is A, that is in
particular . Higher-lying glueballs are shown to
exist only for the A, D and E gauge
algebras. The shape of the static energy between adjoint sources is also
discussed assuming the Casimir scaling hypothesis and a funnel form; it appears
to be gauge-algebra dependent when at least three sources are considered. As a
main result, the present framework's predictions are shown to be consistent
with available lattice data in the particular case of an
gauge algebra within 't Hooft's large- limit.Comment: 21 pages, 4 figures; remarks added, typos corrected in v2. v3 to
appear in EPJ
Effect of Restricted Preen-Gland Access on Maternal Self Maintenance and Reproductive Investment in Mallards
As egg production and offspring care are costly, females should invest resources adaptively into their eggs to optimize current offspring quality and their own lifetime reproductive success. Parasite infections can influence maternal investment decisions due to their multiple negative physiological effects. The act of preening--applying oils with anti-microbial properties to feathers--is thought to be a means by which birds combat pathogens and parasites, but little is known of how preening during the reproductive period (and its expected disease-protecting effects) influences maternal investment decisions at the level of the egg.Here, we experimentally prevented female mallards (Anas platyrhynchos) from accessing their preen gland during breeding and monitored female immunoresponsiveness (e.g., plasma lysozyme concentration) as well as some egg traits linked to offspring quality (e.g., egg mass, yolk carotenoid content, and albumen lysozyme levels). Females with no access to their preen gland showed an increase in plasma lysozyme level compared to control, normally preening females. In addition, preen-gland-restricted females laid significantly lighter eggs and deposited higher carotenoid concentrations in the yolk compared to control females. Albumen lysozyme activity did not differ significantly between eggs laid by females with or without preen gland access.Our results establish a new link between an important avian self-maintenance behaviour and aspects of maternal health and reproduction. We suggest that higher yolk carotenoid levels in eggs laid by preen-gland-restricted females may serve to boost health of offspring that would hatch in a comparatively microbe-rich environment
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