1,181 research outputs found
Algorithmic Bayesian Persuasion
Persuasion, defined as the act of exploiting an informational advantage in
order to effect the decisions of others, is ubiquitous. Indeed, persuasive
communication has been estimated to account for almost a third of all economic
activity in the US. This paper examines persuasion through a computational
lens, focusing on what is perhaps the most basic and fundamental model in this
space: the celebrated Bayesian persuasion model of Kamenica and Gentzkow. Here
there are two players, a sender and a receiver. The receiver must take one of a
number of actions with a-priori unknown payoff, and the sender has access to
additional information regarding the payoffs. The sender can commit to
revealing a noisy signal regarding the realization of the payoffs of various
actions, and would like to do so as to maximize her own payoff assuming a
perfectly rational receiver.
We examine the sender's optimization task in three of the most natural input
models for this problem, and essentially pin down its computational complexity
in each. When the payoff distributions of the different actions are i.i.d. and
given explicitly, we exhibit a polynomial-time (exact) algorithm, and a
"simple" -approximation algorithm. Our optimal scheme for the i.i.d.
setting involves an analogy to auction theory, and makes use of Border's
characterization of the space of reduced-forms for single-item auctions. When
action payoffs are independent but non-identical with marginal distributions
given explicitly, we show that it is #P-hard to compute the optimal expected
sender utility. Finally, we consider a general (possibly correlated) joint
distribution of action payoffs presented by a black box sampling oracle, and
exhibit a fully polynomial-time approximation scheme (FPTAS) with a bi-criteria
guarantee. We show that this result is the best possible in the black-box model
for information-theoretic reasons
Turbulence near cyclic fold bifurcations in birhythmic media
We show that at the onset of a cyclic fold bifurcation, a birhythmic medium
composed of glycolytic oscillators displays turbulent dynamics. By computing
the largest Lyapunov exponent, the spatial correlation function, and the
average transient lifetime, we classify it as a weak turbulence with transient
nature. Virtual heterogeneities generating unstable fast oscillations are the
mechanism of the transient turbulence. In the presence of wavenumber
instability, unstable oscillations can be reinjected leading to stationary
turbulence. We also find similar turbulence in a cell cycle model. These
findings suggest that weak turbulence may be universal in biochemical
birhythmic media exhibiting cyclic fold bifurcations.Comment: 14 pages 10 figure
Rigorous approach to the comparison between experiment and theory in Casimir force measurements
In most experiments on the Casimir force the comparison between measurement
data and theory was done using the concept of the root-mean-square deviation, a
procedure that has been criticized in literature. Here we propose a special
statistical analysis which should be performed separately for the experimental
data and for the results of the theoretical computations. In so doing, the
random, systematic, and total experimental errors are found as functions of
separation, taking into account the distribution laws for each error at 95%
confidence. Independently, all theoretical errors are combined to obtain the
total theoretical error at the same confidence. Finally, the confidence
interval for the differences between theoretical and experimental values is
obtained as a function of separation. This rigorous approach is applied to two
recent experiments on the Casimir effect.Comment: 10 pages, iopart.cls is used, to appear in J. Phys. A (special issue:
Proceedings of QFEXT05, Barcelona, Sept. 5-9, 2005
Possibility of measuring the thermal Casimir interaction between a plate and a cylinder attached to a micromachined oscillator
We investigate the possibility of measuring the thermal Casimir force and its
gradient in the configuration of a plate and a microfabricated cylinder
attached to a micromachined oscillator. The Lifshitz-type formulas in this
configuration are derived using the proximity force approximation. The accuracy
for the obtained expressions is determined from a comparison with exact results
available in ideal metal case. Computations of the thermal correction to both
the Casimir force and its gradient are performed in the framework of different
theoretical approaches proposed in the literature. The correction to the
Casimir force and its gradient due to lack of parallelism of the plate and
cylinder is determined using the nonmultiplicative approach. The error
introduced in the theory due to the finite length of the cylinder is estimated.
We propose that both static and dynamic experiments measuring the thermal
Casimir interaction between a cylinder and a plate using a micromachined
oscillator can shed additional light on the thermal Casimir force problem.
Specifically, it is shown that the static experiment is better adapted for the
measurement of thermal effects.Comment: 29 pages, 4 figures, 1 table; minor additions are made in accordance
to the version accepted for publication; to appear in Phys. Rev.
Chaotic Phenomenon in Nonlinear Gyrotropic Medium
Nonlinear gyrotropic medium is a medium, whose natural optical activity
depends on the intensity of the incident light wave. The Kuhn's model is used
to study nonlinear gyrotropic medium with great success. The Kuhn's model
presents itself a model of nonlinear coupled oscillators. This article is
devoted to the study of the Kuhn's nonlinear model. In the first paragraph of
the paper we study classical dynamics in case of weak as well as strong
nonlinearity. In case of week nonlinearity we have obtained the analytical
solutions, which are in good agreement with the numerical solutions. In case of
strong nonlinearity we have determined the values of those parameters for which
chaos is formed in the system under study. The second paragraph of the paper
refers to the question of the Kuhn's model integrability. It is shown, that at
the certain values of the interaction potential this model is exactly
integrable and under certain conditions it is reduced to so-called universal
Hamiltonian. The third paragraph of the paper is devoted to quantum-mechanical
consideration. It shows the possibility of stochastic absorption of external
field energy by nonlinear gyrotropic medium. The last forth paragraph of the
paper is devoted to generalization of the Kuhn's model for infinite chain of
interacting oscillators
Galectin-1 as a potential cancer target
Galectins are a family of structurally related carbohydrate-binding proteins, which are defined by their affinity for poly-N-acetyllactosamine-enriched glycoconjugates and sequence similarities in the carbohydrate recognition domain. Galectin-1, a member of this family, contributes to different events associated with cancer biology, including tumour transformation, cell cycle regulation, apoptosis, cell adhesion, migration and inflammation. In addition, recent evidence indicates that galectin-1 contributes to tumour evasion of immune responses. Given the increased interest of tumour biologists and clinical oncologists in this field and the potential use of galectins as novel targets for anticancer drugs, we summarise here recent advances about the role of galectin-1 in different events of tumour growth and metastasis
Critical dimensions for random walks on random-walk chains
The probability distribution of random walks on linear structures generated
by random walks in -dimensional space, , is analytically studied
for the case . It is shown to obey the scaling form
, where is
the density of the chain. Expanding in powers of , we find that
there exists an infinite hierarchy of critical dimensions, ,
each one characterized by a logarithmic correction in . Namely, for
, ; for ,
; for , ; for , ; for , , {\it etc.\/} In particular, for
, this implies that the temporal dependence of the probability density of
being close to the origin .Comment: LATeX, 10 pages, no figures submitted for publication in PR
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..
Fredholmness of Toeplitz operators on the Fock space
The Fredholm property of Toeplitz operators on the -Fock spaces on is studied. A general Fredholm criterion for arbitrary operators from the Toeplitz algebra on in terms of the invertibility of limit operators is derived. This paper is based on previous work, which establishes corresponding results on the unit balls
Frozen spatial chaos induced by boundaries
We show that rather simple but non-trivial boundary conditions could induce
the appearance of spatial chaos (that is stationary, stable, but spatially
disordered configurations) in extended dynamical systems with very simple
dynamics. We exemplify the phenomenon with a nonlinear reaction-diffusion
equation in a two-dimensional undulated domain. Concepts from the theory of
dynamical systems, and a transverse-single-mode approximation are used to
describe the spatially chaotic structures.Comment: 9 pages, 6 figures, submitted for publication; for related work visit
http://www.imedea.uib.es/~victo
- …