35,902 research outputs found
at large : from curve counts to quantum modularity
Reducing a 6d fivebrane theory on a 3-manifold gives a -series
3-manifold invariant . We analyse the large- behaviour of
, where is the complement of a knot in the
3-sphere, and explore the relationship between an -deformed ()
version of and HOMFLY-PT polynomials. On the one hand, in combination
with counts of holomorphic annuli on knot complements, this gives an
enumerative interpretation of in terms of counts of open holomorphic
curves. On the other, it leads to closed form expressions for -deformed
for -torus knots. They suggest a further -deformation based
on superpolynomials, which can be used to obtain a -deformation of ADO
polynomials, expected to be related to categorification. Moreover, studying how
transforms under natural geometric operations on indicates relations
to quantum modularity in a new setting.Comment: 42 pages, 4 figure
Sectoral Productivity and Real Exchange Rate Appreciation: Much Ado about Nothing?
Using panel data for selected national economies, we estimate relative price changes stemming from fluctuations in sectoral productivity. Subsequently, we calculate the cross-country CPIinflation differentials implied by sectorally unbalanced productivity growth, taking into account country-specific weights of non-tradables in consumption (value added) and assuming there are no adjustments in nominal exchange rates. We find that sectoral productivity developments have a statistically significant impact on relative prices in the EU countries and also in the Czech Republic, but the magnitude of the impact is not as strong as the Balassa-Samuelson Effect (BSEF) would predict. The final impact of relative productivity on inflation (on the real exchange rate) is even weaker, and moreover, in the case of the Czech Republic the impact is negligible. Thus, contrary to the prevailing view, we question the meaning of the BSEF as a plausible explanatory variable of (equilibrium) real exchange rate determination in the Czech Republic. The same situation we simulate for the future, should productivity growth in the traded sector not accelerate dramatically.Balassa-Samuelson Effect, cross-country inflation differentials, nominal and real convergence, real exchange rates.
Testing excitation models of rapidly oscillating Ap stars with interferometry
Rapidly oscillating Ap stars are unique objects in the potential they offer
to study the interplay between a number of important physical phenomena, in
particular, pulsations, magnetic fields, diffusion, and convection.
Nevertheless, the simple understanding of how the observed pulsations are
excited in these stars is still in progress. In this work we perform a test to
what is possibly the most widely accepted excitation theory for this class of
stellar pulsators. The test is based on the study of a subset of members of
this class for which stringent data on the fundamental parameters are available
thanks to interferometry. For three out of the four stars considered in this
study, we find that linear, non-adiabatic models with envelope convection
suppressed around the magnetic poles can reproduce well the frequency region
where oscillations are observed. For the fourth star in our sample no agreement
is found, indicating that a new excitation mechanism must be considered. For
the three stars whose observed frequencies can be explained by the excitation
models under discussion, we derive the minimum angular extent of the region
where convection must be suppressed. Finally, we find that the frequency
regions where modes are expected to be excited in these models is very
sensitive to the stellar radius. This opens the interesting possibility of
determining this quantity and related ones, such as the effective temperature
or luminosity, from comparison between model predictions and observations, in
other targets for which these parameters are not well determined.Comment: Accepted for publication in the MNRA
Modeling Eridani and asteroseismic tests of element diffusion
Taking into account the helium and metal diffusion, we explore the possible
evolutionary status and perform seismic analysis of MOST target: the star
Eridani. We adopt the different input parameters to construct the
models by fitting the available observational constraints: e.g., ,
, , . From computation, we obtain the average large spacings of
Eridani about Hz. The age of the diffused models has
been found to be about 1 Gyr, which is younger than one determined previously
by models without diffusion. We found that the effect of pure helium diffusion
on the internal structure of the young low-mass star is slight, but the metal
diffusion influence is obvious. The metal diffusion leads the models to have
much higher temperature in the radiation interior, correspondingly the higher
sound speed in the interior of the model, thereby the larger frequency and
spacings.Comment: 16 pages, 4 figures, accepted for publication in ChjA
The dynamics of single spike-evoked adenosine release in the cerebellum
The purine adenosine is a potent neuromodulator in the brain, with roles in a number
of diverse physiological and pathological processes. Modulators such as adenosine are difficult
to study as once released they have a diffuse action (which can affect many neurones) and,
unlike classical neurotransmitters, have no inotropic receptors. Thus rapid postsynaptic currents
(PSCs) mediated by adenosine (equivalent to mPSCs) are not available for study. As a result
the mechanisms and properties of adenosine release still remain relatively unclear. We have
studied adenosine release evoked by stimulating the parallel fibres in the cerebellum. Using
adenosine biosensors combined with deconvolution analysis and mathematical modelling, we
have characterised the release dynamics and diffusion of adenosine in unprecedented detail.
By partially blocking K+ channels, we were able to release adenosine in response to a single
stimulus rather than a train of stimuli. This allowed reliable sub-second release of reproducible
quantities of adenosine with stereotypic concentration waveforms that agreed well with predictions
of a mathematical model of purine diffusion. We found no evidence for ATP release
and thus suggest that adenosine is directly released in response to parallel fibre firing and does
not arise from extracellular ATP metabolism. Adenosine release events showed novel short-term
dynamics, including facilitated release with paired stimuli at millisecond stimulation intervals
but depletion-recovery dynamics with paired stimuli delivered over minute time scales. These
results demonstrate rich dynamics for adenosine release that are placed, for the first time, on a
quantitative footing and show strong similarity with vesicular exocytosis
Fingering convection induced by atomic diffusion in stars: 3D numerical computations and applications to stellar models
Iron-rich layers are known to form in the stellar subsurface through a
combination of gravitational settling and radiative levitation. Their presence,
nature and detailed structure can affect the excitation process of various
stellar pulsation modes, and must therefore be modeled carefully in order to
better interpret Kepler asteroseismic data. In this paper, we study the
interplay between atomic diffusion and fingering convection in A-type stars,
and its role in the establishment and evolution of iron accumulation layers. To
do so, we use a combination of three-dimensional idealized numerical
simulations of fingering convection, and one-dimensional realistic stellar
models. Using the three-dimensional simulations, we first validate the mixing
prescription for fingering convection recently proposed by Brown et al. (2013),
and identify what system parameters (total mass of iron, iron diffusivity,
thermal diffusivity, etc.) play a role in the overall evolution of the layer.
We then implement the Brown et al. (2013) prescription in the Toulouse-Geneva
Evolution code to study the evolution of the iron abundance profile beneath the
stellar surface. We find, as first discussed by Th\'eado et al. (2009), that
when the concurrent settling of helium is ignored, this accumulation rapidly
causes an inversion in the mean molecular weight profile, which then drives
fingering convection. The latter mixes iron with the surrounding material very
efficiently, and the resulting iron layer is very weak. However, taking helium
settling into account partially stabilizes the iron profile against fingering
convection, and a large iron overabundance can accumulate. The opacity also
increases significantly as a result, and in some cases ultimately triggers
dynamical convection.Comment: 38 pages, 16 figures, submitted to Ap
Beyond Structural Causal Models: Causal Constraints Models
Structural Causal Models (SCMs) provide a popular causal modeling framework.
In this work, we show that SCMs are not flexible enough to give a complete
causal representation of dynamical systems at equilibrium. Instead, we propose
a generalization of the notion of an SCM, that we call Causal Constraints Model
(CCM), and prove that CCMs do capture the causal semantics of such systems. We
show how CCMs can be constructed from differential equations and initial
conditions and we illustrate our ideas further on a simple but ubiquitous
(bio)chemical reaction. Our framework also allows to model functional laws,
such as the ideal gas law, in a sensible and intuitive way.Comment: Published in Proceedings of the 35th Annual Conference on Uncertainty
in Artificial Intelligence (UAI-19
Gender equality and investments in adolescents in the rural Philippines:
"...Many studies have looked at the way resources are distributed to men, women, and especially to small children, but one age group within the family has been largely ignored: the adolescents. Adolescence is a crucial period in that teenagers can make major contributions to their families' welfare through their labor and earnings, in and outside the household, but may sacrifice their own wishes and future well-being in the process if such contributions come at the expense of investments in their education. The research methodology in this report, combining regression analysis with ethnography, provides a lesson in how complementarities between methodological approaches can be exploited...The research finds that parents are not unduly influenced by short-term needs and are ready to make substantial sacrifices in terms of current consumption in order to invest in their children's future. The research also concludes that boys and girls in this rural area of the Philippines are generally treated equally, provid ing a contrast with other Asian settings where discrimination by gender is common." (Forward by Per Pinstrup- Andersen)Teenagers Philippines Social conditions., Rural families Philippines., Gender, Health and nutrition, Education Economic aspects Philippines., Household resource allocation, Health.,
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