9,784 research outputs found
Comment on "Critical and slow dynamics in a bulk metallic glass exhibiting strong random magnetic anisotropy" [Appl. Phys. Lett. 92, 011923 (2008)]
In this comment, by using Monte Carlo simulation, we show that the
perpendicular shift of hysteresis loops reported in the commented work is
nothing special but simply due to the fact that the range of field does not
surpass the reversible field beyond which the two branches of the loop merge.
If the reversible field is exceeded, the shift is no longer observed. Moreover,
we point out that even using a small range of field, the shift will not be
observed if the observation time is long enough for the reversible field to
drop within the range.Comment: 2 pages, 2 figures, accepted for publication in Applied Physics
Letters Volume 94, Issue 15, Issue date 13 April 200
Mangetic phase transition for three-dimensional Heisenberg weak random anisotropy model: Monte Carlo study
Magnetic phase transition (MPT) to magnetic quasi-long-range order (QLRO)
phase in a three-dimensional Heisenberg weak (D/J=4) random anisotropy (RA)
model is investigated by Monte Carlo simulation. The isotropic and cubic
distributions of RA axes are considered for simple-cubic-lattice systems.
Finite-size scaling analysis shows that the critical couplings for the former
and latter are K_c= 0.70435(2) and K_c=0.70998(4), respectively. While the
critical exponent 1/\nu =1.40824(0) is the same for both cases. A second-order
MPT to the QLRO phase is therefore evidenced to be possible in favor with the
existence of the QLRO predicted by recent functional renormalization group
theories.Comment: 9 pages, 3 figures. to be appeared in Journal of Applied Physics
Volume 105 Issue 7 on April 1, 200
An ac field probe for the magnetic ordering of magnets with random anisotropy
A Monte Carlo simulation is carried out to investigate the magnetic ordering
in magnets with random anisotropy (RA). Our results show peculiar similarities
to recent experiments that the real part of ac susceptibility presents two
peaks for weak RA and only one for strong RA regardless of glassy critical
dynamics manifested for them. We demonstrate that the thermodynamic nature of
the low-temperature peak is a ferromagnetic-like dynamic phase transition to
quasi-long range order (QLRO) for the former. Our simulation, therefore, is
able to be incorporated with the experiments to help clarify the existence of
the QLRO theoretically predicted so far.Comment: 10 pages, 4 figures, to appear in Appl. Phys. Lett. volume 95, Issue
22, Isue date: 30 November 200
Optimal Auctions with Financially Constrained Bidders
We consider an environment where potential buyers of an indi- visible good have liquidity constraints, in that they cannot pay more than their `budget' regardless of their valuation. A buyer's valuation for the good as well as her budget are her private information. We derive constrained-efficient and revenue maximizing auctions for this setting. In general, the optimal auction requires `pooling' both at the top and in the middle despite the maintained assumption of a mono- tone hazard rate. Further, the auctioneer will never¯find it desirable to subsidize bidders with low budgets.the universal type space, the strategic topology; the uniform strategic topology; the uniform-weak topology; interim correlated rationalizable actions
Localization in fractonic random circuits
We study the spreading of initially-local operators under unitary time
evolution in a 1d random quantum circuit model which is constrained to conserve
a charge and its dipole moment, motivated by the quantum dynamics of
fracton phases. We discover that charge remains localized at its initial
position, providing a crisp example of a non-ergodic dynamical phase of random
circuit dynamics. This localization can be understood as a consequence of the
return properties of low dimensional random walks, through a mechanism
reminiscent of weak localization, but insensitive to dephasing. The charge
dynamics is well-described by a system of coupled hydrodynamic equations, which
makes several nontrivial predictions in good agreement with numerics.
Importantly, these equations also predict localization in 2d fractonic
circuits. Immobile fractonic charge emits non-conserved operators, whose
spreading is governed by exponents distinct to non-fractonic circuits.
Fractonic operators exhibit a short time linear growth of observable
entanglement with saturation to an area law, as well as a subthermal volume law
for operator entanglement. The entanglement spectrum follows semi-Poisson
statistics, similar to eigenstates of MBL systems. The non-ergodic
phenomenology persists to initial conditions containing non-zero density of
dipolar or fractonic charge. Our work implies that low-dimensional fracton
systems preserve forever a memory of their initial conditions in local
observables under noisy quantum dynamics, thereby constituting ideal memories.
It also implies that 1d and 2d fracton systems should realize true MBL under
Hamiltonian dynamics, even in the absence of disorder, with the obstructions to
MBL in translation invariant systems and in d>1 being evaded by the nature of
the mechanism responsible for localization. We also suggest a possible route to
new non-ergodic phases in high dimensions.Comment: Appended erratu
Axillary Arch (Of Langer): Incidence, Innervation, Importance
The present study was planned to find out the incidence of accessory muscle arches in the axilla of 68 upper limb (38 right and 30 left) dissections. Langer’s arch was observed in one right limb out of the 68 limbs, total incidence was 1.47%. The arch extended from the latissimus dorsi to the fascia covering the biceps brachii. The incidence is low in South Indian population (Dravidians) compared to the various other populations reported in literature. A branch from the lateral cord of brachial plexus supplied it in contrast with the previous reports. The surgical significance of this muscle is reviewe
Unfolding Polyelectrolytes in Trivalent Salt Solutions Using DC Electric Fields: A Study by Langevin Dynamics Simulations
We study the behavior of single linear polyelectrolytes condensed by
trivalent salt under the action of electric fields through computer
simulations. The chain is unfolded when the strength of the electric field is
stronger than a critical value. This critical electric field follows a scaling
law against chain length and the exponent of the scaling law is ,
smaller than the theoretical prediction, [Netz, Phys. Rev. Lett. 90
(2003) 128104], and the one obtained by simulations in tetravalent salt
solutions, [Hsiao and Wu, J. Phys. Chem. B 112 (2008) 13179]. It
demonstrates that the scaling exponent depends sensitively on the salt valence.
Hence, it is easier to unfold chains condensed by multivalent salt of smaller
valence. Moreover, the absolute value of chain electrophoretic mobility
increases drastically when the chain is unfolded in an electric field. The
dependence of the mobility on electric field and chain length provides a
plausible way to impart chain-length dependence in free-solution
electrophoresis via chain unfolding transition induced by electric fields.
Finally, we show that, in addition to an elongated structure, a condensed chain
can be unfolded into an U-shaped structure. The formation of this structure in
our study is purely a result of the electric polarization, but not of the
elasto-hydrodynamics dominated in sedimentation of polymers.Comment: 15 pages, 7 figures, accepted for publication in Biomicrofluidic
The Strange Case of Privacy in Equilibrium Models
We study how privacy technologies affect user and advertiser behavior in a
simple economic model of targeted advertising. In our model, a consumer first
decides whether or not to buy a good, and then an advertiser chooses an
advertisement to show the consumer. The consumer's value for the good is
correlated with her type, which determines which ad the advertiser would prefer
to show to her---and hence, the advertiser would like to use information about
the consumer's purchase decision to target the ad that he shows.
In our model, the advertiser is given only a differentially private signal
about the consumer's behavior---which can range from no signal at all to a
perfect signal, as we vary the differential privacy parameter. This allows us
to study equilibrium behavior as a function of the level of privacy provided to
the consumer. We show that this behavior can be highly counter-intuitive, and
that the effect of adding privacy in equilibrium can be completely different
from what we would expect if we ignored equilibrium incentives. Specifically,
we show that increasing the level of privacy can actually increase the amount
of information about the consumer's type contained in the signal the advertiser
receives, lead to decreased utility for the consumer, and increased profit for
the advertiser, and that generally these quantities can be non-monotonic and
even discontinuous in the privacy level of the signal
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