5,657 research outputs found
On Eigenvalue spacings for the 1-D Anderson model with singular site distribution
We study eigenvalue spacings and local eigenvalue statistics for 1D lattice
Schrodinger operators with Holder regular potential, obtaining a version of
Minami's inequality and Poisson statistics for the local eigenvalue spacings.
The main additional new input are regular properties of the Furstenberg
measures and the density of states obtained in some of the author's earlier
work.Comment: 13 page
The Master Equation for Large Population Equilibriums
We use a simple N-player stochastic game with idiosyncratic and common noises
to introduce the concept of Master Equation originally proposed by Lions in his
lectures at the Coll\`ege de France. Controlling the limit N tends to the
infinity of the explicit solution of the N-player game, we highlight the
stochastic nature of the limit distributions of the states of the players due
to the fact that the random environment does not average out in the limit, and
we recast the Mean Field Game (MFG) paradigm in a set of coupled Stochastic
Partial Differential Equations (SPDEs). The first one is a forward stochastic
Kolmogorov equation giving the evolution of the conditional distributions of
the states of the players given the common noise. The second is a form of
stochastic Hamilton Jacobi Bellman (HJB) equation providing the solution of the
optimization problem when the flow of conditional distributions is given. Being
highly coupled, the system reads as an infinite dimensional Forward Backward
Stochastic Differential Equation (FBSDE). Uniqueness of a solution and its
Markov property lead to the representation of the solution of the backward
equation (i.e. the value function of the stochastic HJB equation) as a
deterministic function of the solution of the forward Kolmogorov equation,
function which is usually called the decoupling field of the FBSDE. The
(infinite dimensional) PDE satisfied by this decoupling field is identified
with the \textit{master equation}. We also show that this equation can be
derived for other large populations equilibriums like those given by the
optimal control of McKean-Vlasov stochastic differential equations. The paper
is written more in the style of a review than a technical paper, and we spend
more time and energy motivating and explaining the probabilistic interpretation
of the Master Equation, than identifying the most general set of assumptions
under which our claims are true
Large deviations for clocks of self-similar processes
The Lamperti correspondence gives a prominent role to two random time
changes: the exponential functional of a L\'evy process drifting to
and its inverse, the clock of the corresponding positive self-similar process.
We describe here asymptotical properties of these clocks in large time,
extending the results of Yor and Zani
Noncommutative fields in three dimensions and mass generation
We apply the noncommutative fields method for gauge theory in three
dimensions where the Chern-Simons term is generated in the three-dimensional
electrodynamics. Under the same procedure, the Chern-Simons term is shown to be
cancelled in the Maxwell-Chern-Simons theory for the appropriate value of the
noncommutativity parameter. Hence the mutual interchange between
Maxwell-Chern-Simons theory and pure Maxwell theory turns out to be generated
within this method.Comment: Comments 5 pages, epl, version accepted for publication in
Europhysics Letter
Singular diffusion and criticality in a confined sandpile
We investigate the behavior of a two-state sandpile model subjected to a
confining potential in one and two dimensions. From the microdynamical
description of this simple model with its intrinsic exclusion mechanism, it is
possible to derive a continuum nonlinear diffusion equation that displays
singularities in both the diffusion and drift terms. The stationary-state
solutions of this equation, which maximizes the Fermi-Dirac entropy, are in
perfect agreement with the spatial profiles of time-averaged occupancy obtained
from model numerical simulations in one as well as in two dimensions.
Surprisingly, our results also show that, regardless of dimensionality, the
presence of a confining potential can lead to the emergence of typical
attributes of critical behavior in the two-state sandpile model, namely, a
power-law tail in the distribution of avalanche sizes.Comment: 5 pages, 5 figure
What does it mean to be a “citizen of the world”: A prototype approach
The superordinate social category “citizen of the world” is used by laypeople and scholars to embody several constructs (e.g., cosmopolitanism; global identity and citizenship), and prior research suggests that the concept is better represented as a prototype rather than having a clear-cut definition. This research aims to systematically examine the prototypical meaning of this social category, and how it is cognitively processed. Relying on a prototype approach, six studies (n = 448) showed that certain attributes of this category were communicated more frequently and were regarded as more central (e.g., multiculturalism), and that central (vs. peripheral) attributes were more quickly identified, more often remembered, and more appropriate to identify a group member, as well as the self, as a “citizen of the world.” These results systematically demonstrated that this category has a prototypical structure and there is a differentiated cognitive automatic processing for central and peripheral attributes. We propose that the specific content activated by the attributes regarded as central to the prototype of “citizens of the world” (e.g., intercultural contact; diversity), and the fact that these are more accessible in memory to form a mental representation, are important aspects to understand identity processes and their impact on intergroup outcomes.info:eu-repo/semantics/publishedVersio
Grain growth in newly discovered young eruptive stars
FU Orionis-type stars are young stellar objects showing large outbursts due
to highly enhanced accretion from the circumstellar disk onto the protostar.
FUor-type outbursts happen in a wide variety of sources from the very embedded
ones to those with almost no sign of extended emission beyond the disk. The
subsequent eruptions might gradually clear up the obscuring envelope material
and drive the protostar on its way to become a disk-only T Tauri star. We used
VLT/VISIR to obtain the first spectra that cover the 8-13 m mid-infrared
wavelength range in low-resolution of five recently discovered FUors. Four
objects from our sample show the 10 m silicate feature in emission. We
study the shape and strength of the silicate feature in these objects and find
that they mostly contain large amorphous grains, suggesting that large grains
are typically not settled to the midplane in FUor disks. This is a general
characteristic of FUors, as opposed to regular T Tauri-type stars whose disks
display anything from pristine small grains to significant grain growth. We
classify our targets by determining whether the silicate feature is in emission
or in absorption, and confront them with the evolutionary scenarios on the
dispersal of the envelopes around young stars. In our sample, all Class II
objects exhibit silicate emission, while for Class I objects, the appearance of
the feature in emission or absorption depends on the viewing angle with respect
to the outflow cavity. This highlights the importance of geometric effects when
interpreting the silicate feature.Comment: 7 pages, 1 table, 3 figures, accepted for publication in the
Astrophysical Journal Letter
Activation of H-H, HO-H, C(sp2)-H, C(sp3)-H, and RO-H bonds by transition-metal frustrated lewis pairs based onon M/N (M = Rh, Ir) couples
Reaction of the dimers (Cp*MCl)2(µ-Cl)2] (Cp* = 5-C5Me5) with Ph2PCH2CH2NC(NH(p-Tolyl))2 (H2L) in the presence of NaSbF6 affords the chlorido complexes Cp*MCl(¿2N, P-H2L)]SbF6] (M = Rh, 1; Ir, 2). Upon treatment with aqueous NaOH, solutions of 1 and 2 yield the corresponding complexes Cp*M(¿3N, N', P-HL)]SbF6] (M = Rh, 3; Ir, 4) in which the ligand HL presents a fac ¿3N, N', P coordination mode. Treatment of THF solutions of complexes 3 and 4 with hydrogen gas, at room temperature, results in the formation of the metal hydrido-complexes Cp*MH(¿2N, P-H2L)]SbF6] (M = Rh, 5; Ir, 6) in which the N(p-Tolyl) group has been protonated. Complexes 3 and 4 react with deuterated water in a reversible fashion resulting in the gradual deuteration of the Cp* group. Heating at 383 K THF/H2O solutions of the complexes 3 and 4 affords the orthometalated complexes Cp*M(¿3C, N, P-H2L-H)]SbF6] M = Rh, 7; Ir, 8, H2L-H = Ph2PCH2CH2NC(NH(p-Tolyl))(NH(4-C6H3Me))], respectively. At 333 K, complexes 3 and 4 react in THF with methanol, primary alcohols, or 2-propanol giving the metal-hydrido complexes 5 and 6, respectively. The reaction involves the acceptorless dehydrogenation of the alcohols at a relatively low temperature, without the assistance of an external base. The new complexes have been characterized by the usual analytical and spectroscopic methods including the X-ray diffraction determination of the crystal structures of complexes 1-5, 7, and 8. Notably, the chlorido complexes 1 and 2 crystallize both as enantiopure conglomerates and as racemates. Reaction mechanisms are proposed based on stoichiometric reactions, nuclear magnetic resonance studies, and X-ray crystallography as well as density functional theory calculations. © 2022 The Authors. Published by American Chemical Society
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