4,432 research outputs found
Nature of the first excited state of He-4
We study the first excited state of He4 in a microscopic {H3+p,He3+n} cluster
model, including H3 and He3 distortions. The phenomenological 1S0 H3+p
scattering phase shift is well reproduced. We localize a complex pole of the
S-matrix between the H3+p and He3+n thresholds. The corresponding resonance
parameters are E_r=93 keV position relative to H3+p, and Gamma=390 keV width. A
pole search is also performed in an extended R-matrix method, and a resonance
is found with parameters E_r=114 keV and Gamma=392 keV. The R-matrix approach
gives several additional poles, some of which may be connected with an enhanced
threshold effect.Comment: 13 pages, 2 figure
Why (and When) are Preferences Convex? Threshold Effects and Uncertain Quality
It is often assumed (for analytical convenience, but also in accordance with common intuition) that consumer preferences are convex. In this paper, we consider circumstances under which such preferences are (or are not) optimal. In particular, we investigate a setting in which goods possess
some hidden quality with known distribution, and the consumer chooses a bundle of goods that
maximizes the probability that he receives some threshold level of this quality. We show that if the
threshold is small relative to consumption levels, preferences will tend to be convex; whereas the
opposite holds if the threshold is large. Our theory helps explain a broad spectrum of economic behavior (including, in particular, certain common commercial advertising strategies), suggesting
that sensitivity to information about thresholds is deeply rooted in human psychology
Asymptotic normality of additive functions on polynomial sequences in canonical number systems
The objective of this paper is the study of functions which only act on the
digits of an expansion. In particular, we are interested in the asymptotic
distribution of the values of these functions. The presented result is an
extension and generalization of a result of Bassily and K\'atai to number
systems defined in a quotient ring of the ring of polynomials over the
integers.Comment: 17 page
Broken ergodicity in driven one-dimensional particle systems with short-range interaction
We present a one-dimensional nonequilibrium model for a driven
di�usive system which has local interactions and slow nonconservative reaction
kinetics. Monte-Carlo simulations suggest that in the thermodynamic limit
the steady state exhibits a phase with broken ergodicity. We propose a hydrodynamic
equation for the coarse-grained density (under Eulerian scaling),
augmented by a prescription how to treat shock and boundary discontinuities,
respectively. This conjecture can be readily generalized to other weakly nonconservative
driven di�usive systems and is supported by a heuristic identi�cation
of the main dynamical mode that governs the microscopic dynamics, viz. the
random motion of a shock in an self-organized e�ective potential. This picture
leads to the exact phase diagram of the system and suggests a novel and
mathematically tractable mechanism for \freezing by heating"
Impact of critical mass on the evolution of cooperation in spatial public goods games
We study the evolution of cooperation under the assumption that the
collective benefits of group membership can only be harvested if the fraction
of cooperators within the group, i.e. their critical mass, exceeds a threshold
value. Considering structured populations, we show that a moderate fraction of
cooperators can prevail even at very low multiplication factors if the critical
mass is minimal. For larger multiplication factors, however, the level of
cooperation is highest at an intermediate value of the critical mass. The
latter is robust to variations of the group size and the interaction network
topology. Applying the optimal critical mass threshold, we show that the
fraction of cooperators in public goods games is significantly larger than in
the traditional linear model, where the produced public good is proportional to
the fraction of cooperators within the group.Comment: 4 two-column pages, 4 figures; accepted for publication in Physical
Review
A Theory of Natural Addiction
Economic theories of rational addiction aim to describe consumer behavior in the presence of habit-forming goods. We provide a biological foundation for this body of work by formally specifying conditions under which it is optimal to form a habit. We demonstrate the empirical validity of our thesis with an in-depth review and synthesis of the biomedical literature concerning the action of opiates in the mammalian brain and their e ects on behavior. Our results lend credence to many of the unconventional behavioral assumptions employed by theories of rational addiction, including adjacent complementarity and the importance of cues, attention, and self-control in determining the behavior of addicts. Our approach suggests, however, that addiction is 'harmful' only when the addict fails to implement the optimal solution. We offer evidence for the special case of the opiates that harmful addiction is the manifestation of a mismatch between behavioral algorithms encoded in the human genome and the expanded menu of choices- -generated for example, by advances in drug delivery technology--faced by consumers in the modern world.self-control, endogenous opioids, addiction, behavioral ecology, neuroeconomics, autism
Opportunity Knocks: An Economic Analysis of Television Advertisements
Certain aspects of advertising–especially on television–are not easily explained with conventional economic models. In particular, much of the imagery and repetitive thematic content seen in advertisements suggests it is "psychological" in nature, as opposed to "informative". To understand the economic rationale for incorporating such material, we develop a theory of preferences in which information about threshold payoffs induces
sudden shifts in demand. These threshold payoffs are best understood in the context of human evolutionary history. Furthermore, the presence of threshold payoffs in consumer
preferences gives firms incentive for providing threshold-type information. To examine
the use of threshold-related content in television advertisements, we look for this con-
tent in a sample of 370 television advertisements. We find considerable evidence that advertisers make strategic use of threshold-type content in television advertisements. Specifically, threshold-related content occurred in 83% of food and beverage advertisements for children and in 71% of advertisements for general audiences. Furthermore, the threshold-related content in children’s food and beverage advertisements occurred with statistically greater frequency than factual content, which isn’t true for food and beverage advertisements for general audiences
A Theory of Natural Addiction
Economic theories of rational addiction aim to describe consumer behavior in the presence of habit-forming goods. We provide a biological foundation for this body of work by formally specifying conditions under which it is optimal to form a habit. We demonstrate the empirical validity of our thesis with an in-depth review and synthesis of the biomedical literature concerning the action of opiates in the mammalian brain and their effects on behavior. Our results lend credence to many of the unconventional behavioral assumptions employed by theories of rational addiction, including adjacent complementarity and the importance of cues, attention, and self-control in determining the behavior of addicts. Our approach suggests, however, that addiction is "harmful" only when the addict fails to implement the optimal solution. We offer evidence for the special case of the opiates that harmful addiction is the manifestation of a mismatch between behavioral algorithms encoded in the human genome and the expanded menu of choicesgenerated for example, by advances in drug delivery technology faced by consumers in the modern world.Consumer/Household Economics,
Quantum entanglement in strong-field ionization
We investigate the time-evolution of quantum entanglement between an
electron, liberated by a strong few-cycle laser pulse, and its parent ion-core.
Since the standard procedure is numerically prohibitive in this case, we
propose a novel way to quantify the quantum correlation in such a system: we
use the reduced density matrices of the directional subspaces along the
polarization of the laser pulse and along the transverse directions as building
blocks for an approximate entanglement entropy. We present our results, based
on accurate numerical simulations, in terms of several of these entropies, for
selected values of the peak electric field strength and the carrier-envelope
phase difference of the laser pulse. The time evolution of the mutual entropy
of the electron and the ion-core motion along the direction of the laser
polarization is similar to our earlier results based on a simple
one-dimensional model. However, taking into account also the dynamics
perpendicular to the laser polarization reveals a surprisingly different
entanglement dynamics above the laser intensity range corresponding to pure
tunneling: the quantum entanglement decreases with time in the over-the-barrier
ionization regime
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