2,235 research outputs found
A characterization of intrinsic reciprocity
This paper studies a game-theoretic model in which players have preferences over their strategies. These preferences vary with the strategic context. The paper further assumes that each player has an ordering over an opponent's strategies that describes the niceness of these strategies. It introduces a condition that insures that the weight on an opponent's utility increases if and only if the opponent chooses a nicer strategy. © 2007 Springer Verlag.Segal thanks SSHRCC and Sobel thanks the Guggenheim Foundation, NSF, and the Secretaría de Estado de Universidades e Investigación del Ministerio de Educación y Ciencia (Spain) for financial support.Peer Reviewe
Preferences and social influence
Interaction between decision makers may affect their preferences. We consider a setup in which each individual is characterized by two sets of preferences: his unchanged core preferences and his behavioral preferences. Each individual has a social influence function that determines his behavioral preferences given his core preferences and the behavioral preferences of other individuals in his group. Decisions are made according to behavioral preferences. The paper considers different properties of these social influence functions and their effect on equilibrium behavior. We illustrate the applicability of our model by considering decision making by a committee that has a deliberation stage prior to votin
Wigner function and Schroedinger equation in phase space representation
We discuss a family of quasi-distributions (s-ordered Wigner functions of
Agarwal and Wolf) and its connection to the so called phase space
representation of the Schroedinger equation. It turns out that although Wigner
functions satisfy the Schroedinger equation in phase space they have completely
different interpretation.Comment: 6 page
Quantum fluctuation theorem for heat exchange in the strong coupling regime
We study quantum heat exchange in a multi-state impurity coupled to two
thermal reservoirs. Allowing for strong system-bath interactions, we show that
a steady-state heat exchange fluctuation theorem holds, though the dynamical
processes nonlinearly involve the two reservoirs. We accomplish a closed
expression for the cumulant generating function, and use it obtain the heat
current and its cumulants in a nonlinear thermal junction, the two-bath
spin-boson model
Non-Equilibrium Quantum Dissipation
Dissipative processes in non-equilibrium many-body systems are fundamentally
different than their equilibrium counterparts. Such processes are of great
importance for the understanding of relaxation in single molecule devices. As a
detailed case study, we investigate here a generic spin-fermion model, where a
two-level system couples to two metallic leads with different chemical
potentials. We present results for the spin relaxation rate in the nonadiabatic
limit for an arbitrary coupling to the leads, using both analytical and exact
numerical methods. The non-equilibrium dynamics is reflected by an exponential
relaxation at long times and via complex phase shifts, leading in some cases to
an "anti-orthogonality" effect. In the limit of strong system-lead coupling at
zero temperature we demonstrate the onset of a Marcus-like Gaussian decay with
{\it voltage difference} activation. This is analogous to the equilibrium
spin-boson model, where at strong coupling and high temperatures the spin
excitation rate manifests temperature activated Gaussian behavior. We find that
there is no simple linear relationship between the role of the temperature in
the bosonic system and a voltage drop in a non-equilibrium electronic case. The
two models also differ by the orthogonality-catastrophe factor existing in a
fermionic system, which modifies the resulting lineshapes. Implications for
current characteristics are discussed. We demonstrate the violation of
pair-wise Coulomb gas behavior for strong coupling to the leads. The results
presented in this paper form the basis of an exact, non-perturbative
description of steady-state quantum dissipative systems
Exact dynamics of interacting qubits in a thermal environment: Results beyond the weak coupling limit
We demonstrate an exact mapping of a class of models of two interacting
qubits in thermal reservoirs to two separate spin-bath problems. Based on this
mapping, exact numerical simulations of the qubits dynamics can be performed,
beyond the weak system-bath coupling limit. Given the time evolution of the
system, we study, in a numerically exact way, the dynamics of entanglement
between pair of qubits immersed in boson thermal baths, showing a rich
phenomenology, including an intermediate oscillatory behavior, the entanglement
sudden birth, sudden death, and revival. We find that stationary entanglement
develops between the qubits due to their coupling to a thermal environment,
unlike the isolated qubits case in which the entanglement oscillates. We also
show that the occurrence of entanglement sudden death in this model depends on
the portion of the zero and double excitation states in the subsystem initial
state. In the long-time limit, analytic expressions are presented at weak
system-bath coupling, for a range of relevant qubit parameters
Loop Groups and Discrete KdV Equations
A study is presented of fully discretized lattice equations associated with
the KdV hierarchy. Loop group methods give a systematic way of constructing
discretizations of the equations in the hierarchy. The lattice KdV system of
Nijhoff et al. arises from the lowest order discretization of the trivial,
lowest order equation in the hierarchy, b_t=b_x. Two new discretizations are
also given, the lowest order discretization of the first nontrivial equation in
the hierarchy, and a "second order" discretization of b_t=b_x. The former,
which is given the name "full lattice KdV" has the (potential) KdV equation as
a standard continuum limit. For each discretization a Backlund transformation
is given and soliton content analyzed. The full lattice KdV system has, like
KdV itself, solitons of all speeds, whereas both other discretizations studied
have a limited range of speeds, being discretizations of an equation with
solutions only of a fixed speed.Comment: LaTeX, 23 pages, 1 figur
On the Thermal Symmetry of the Markovian Master Equation
The quantum Markovian master equation of the reduced dynamics of a harmonic
oscillator coupled to a thermal reservoir is shown to possess thermal symmetry.
This symmetry is revealed by a Bogoliubov transformation that can be
represented by a hyperbolic rotation acting on the Liouville space of the
reduced dynamics. The Liouville space is obtained as an extension of the
Hilbert space through the introduction of tilde variables used in the
thermofield dynamics formalism. The angle of rotation depends on the
temperature of the reservoir, as well as the value of Planck's constant. This
symmetry relates the thermal states of the system at any two temperatures. This
includes absolute zero, at which purely quantum effects are revealed. The
Caldeira-Leggett equation and the classical Fokker-Planck equation also possess
thermal symmetry. We compare the thermal symmetry obtained from the Bogoliubov
transformation in related fields and discuss the effects of the symmetry on the
shape of a Gaussian wave packet.Comment: Eqs.(64a), (65a)-(68) are correcte
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Translational outcomes in a full gene deletion of ubiquitin protein ligase E3A rat model of Angelman syndrome.
Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by developmental delay, impaired communication, motor deficits and ataxia, intellectual disabilities, microcephaly, and seizures. The genetic cause of AS is the loss of expression of UBE3A (ubiquitin protein ligase E6-AP) in the brain, typically due to a deletion of the maternal 15q11-q13 region. Previous studies have been performed using a mouse model with a deletion of a single exon of Ube3a. Since three splice variants of Ube3a exist, this has led to a lack of consistent reports and the theory that perhaps not all mouse studies were assessing the effects of an absence of all functional UBE3A. Herein, we report the generation and functional characterization of a novel model of Angelman syndrome by deleting the entire Ube3a gene in the rat. We validated that this resulted in the first comprehensive gene deletion rodent model. Ultrasonic vocalizations from newborn Ube3am-/p+ were reduced in the maternal inherited deletion group with no observable change in the Ube3am+/p- paternal transmission cohort. We also discovered Ube3am-/p+ exhibited delayed reflex development, motor deficits in rearing and fine motor skills, aberrant social communication, and impaired touchscreen learning and memory in young adults. These behavioral deficits were large in effect size and easily apparent in the larger rodent species. Low social communication was detected using a playback task that is unique to rats. Structural imaging illustrated decreased brain volume in Ube3am-/p+ and a variety of intriguing neuroanatomical phenotypes while Ube3am+/p- did not exhibit altered neuroanatomy. Our report identifies, for the first time, unique AS relevant functional phenotypes and anatomical markers as preclinical outcomes to test various strategies for gene and molecular therapies in AS
Equivariant cohomology over Lie groupoids and Lie-Rinehart algebras
Using the language and terminology of relative homological algebra, in
particular that of derived functors, we introduce equivariant cohomology over a
general Lie-Rinehart algebra and equivariant de Rham cohomology over a locally
trivial Lie groupoid in terms of suitably defined monads (also known as
triples) and the associated standard constructions. This extends a
characterization of equivariant de Rham cohomology in terms of derived functors
developed earlier for the special case where the Lie groupoid is an ordinary
Lie group, viewed as a Lie groupoid with a single object; in that theory over a
Lie group, the ordinary Bott-Dupont-Shulman-Stasheff complex arises as an a
posteriori object. We prove that, given a locally trivial Lie groupoid G and a
smooth G-manifold f over the space B of objects of G, the resulting
G-equivariant de Rham theory of f boils down to the ordinary equivariant de
Rham theory of a vertex manifold relative to the corresponding vertex group,
for any vertex in the space B of objects of G; this implies that the
equivariant de Rham cohomology introduced here coincides with the stack de Rham
cohomology of the associated transformation groupoid whence this stack de Rham
cohomology can be characterized as a relative derived functor. We introduce a
notion of cone on a Lie-Rinehart algebra and in particular that of cone on a
Lie algebroid. This cone is an indispensable tool for the description of the
requisite monads.Comment: 47 page
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