434 research outputs found
Nash implementation with partially honest individuals
We investigate the problem of Nash implementation in the presence of "partially honest" individuals. A partially honest player is one who has a strict preference for revealing the true state over lying when truthtelling does not lead to a worse outcome (according to preferences in the true state) than that which obtains when lying. We show that when there are at least three individuals, the presence of even a single partially honest individual (whose identity is not known to the planner) can lead to a dramatic increase in the class of Nash implementable social choice correspondences. In particular, all social choice correspondences satisfying No Veto Power can be implemented. We also provide necessary and sufficient conditions for implementation in the two-person case when there is exactly one partially honest individual and when both individuals are partially honest. We describe some implications of the characterization conditions for the two-person case. Finally, we extend our three or more individual result to the case where there is an individual with an arbitrary small but strictly positive probability of being partially honest
Nash Implementation with Partially Honest Individuals
We investigate the problem of Nash implementation in the presence of "partially honest" individuals. A partially honest player is one who has a strict preference for revealing the true state over lying when truthtelling does not lead to a worse outcome (according to preferences in the true state) than that which obtains when lying. We show that when there are at least three individuals, the presence of even a single partially honest individual (whose identity is not known to the planner) can lead to a dramatic increase in the class of Nash implementable social choice correspondences. In particular, all social choice correspondences satisfying No Veto Power can be implemented. We also provide necessary and sufficient conditions for implementation in the two-person case when there is exactly one partially honest individual and when both individuals are partially honest. We describe some implications of the characterization conditions for the two-person case. Finally, we extend our three or more individual result to the case where there is an individual with an arbitrary small but strictly positive probability of being partially honest.
Glassy Aging with Modified Kohlrausch-Williams-Watts Form
In this report we address the question whether aging in the non equilibrium
glassy state is controlled by the equilibrium alpha-relaxation process which
occur at temperatures above Tg. Recently Lunkenheimer et. al. [Phys. Rev. Lett.
95, 055702 (2005)] proposed a model for the glassy aging data of dielectric
relaxation using a modified Kohlrausch-Williams-Watts (KWW) form. The aging
time dependence of the relaxation time is defined by these authors through a
functional relation involving the corresponding frequency but the stretching
exponent is same as the alpha-relaxation stretching exponent. We present here
an alternative functional form directly involving the relaxation time itself.
The proposed model fits the data of Lunkenheimer et. al. perfectly with a
stretching exponent different from the alpha-relaxation stretching exponent.Comment: 1 TeX file, 10 eps figure
Low-frequency phase diagram of irradiated graphene and periodically driven spin-1/2 chain
We study the Floquet phase diagram of two-dimensional Dirac materials such as
graphene and the one-dimensional (1D) spin-1/2 model in a transverse field
in the presence of periodic time-varying terms in their Hamiltonians in the low
drive frequency () regime where standard perturbative
expansions fail. For graphene, such periodic time dependent terms are generated
via the application of external radiation of amplitude and time period , while for the 1D model, they result from a two-rate drive
protocol with time-dependent magnetic field and nearest-neighbor couplings
between the spins. Using the adiabatic-impulse method, we provide several
semi-analytic criteria for the occurrence of changes in the topology of the
phase bands of such systems. For irradiated graphene, we point out the role of
the symmetries of and behind such topology changes. Our analysis
reveals that at low frequencies, phase band topology changes may also happen at
(apart from ). We chart out the phase diagrams at as a function of and using exact numerics,
and compare them with the prediction of the adiabatic-impulse method. We show
that several characteristics of these phase diagrams can be analytically
understood from results obtained using the adiabatic-impulse method and point
out the crucial contribution of the high-symmetry points in the graphene
Brillouin zone to these diagrams. Finally we study the 1D model with a
two-rate driving protocol using the adiabatic-impulse method and exact numerics
revealing a phase band crossing at and . We also study the
anomalous end modes generated by such a drive. We suggest experiments to test
our theory.Comment: v1; 26 pages, 19 Fig
Plasticity-Induced Magnetization in Amorphous Magnetic Solids
Amorphous magnetic solids, like metallic glasses, exhibit a novel effect: the
growth of magnetic order as a function of mechanical strain under athermal
conditions in the presence of a magnetic field. The magnetic moment increases
in steps whenever there is a plastic event. Thus plasticity induces the
magnetic ordering, acting as the effective noise driving the system towards
equilibrium. We present results of atomistic simulations of this effect in a
model of a magnetic amorphous solid subjected to pure shear and a magnetic
field. To elucidate the dependence on external strain and magnetic field we
offer a mean-field theory that provides an adequate qualitative understanding
of the observed phenomenon
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