2,531 research outputs found
The Functional Architecture of the Brain Underlies Strategic Deception in Impression Management
Impression management, as one of the most essential skills of social function, impacts
one’s survival and success in human societies. However, the neural architecture
underpinning this social skill remains poorly understood. By employing a two-person
bargaining game, we exposed three strategies involving distinct cognitive processes
for social impression management with different levels of strategic deception. We
utilized a novel adaptation of Granger causality accounting for signal-dependent
noise (SDN), which captured the directional connectivity underlying the impression
management during the bargaining game. We found that the sophisticated strategists
engaged stronger directional connectivity from both dorsal anterior cingulate cortex and
retrosplenial cortex to rostral prefrontal cortex, and the strengths of these directional
influences were associated with higher level of deception during the game. Using the
directional connectivity as a neural signature, we identified the strategic deception with
80% accuracy by a machine-learning classifier. These results suggest that different social
strategies are supported by distinct patterns of directional connectivity among key brain
regions for social cognition
Neutrino Condensate as Origin of Dark Energy
We propose a new solution to the origin of dark energy. We suggest that it
was created dynamically from the condensate of a singlet neutrino at a late
epoch of the early Universe through its effective self interaction. This
singlet neutrino is also the Dirac partner of one of the three observed
neutrinos, hence dark energy is related to neutrino mass. The onset of this
condensate formation in the early Universe is also related to matter density
and offers an explanation of the coincidence problem of why dark energy (70%)
and total matter (30%) are comparable at the present time. We demonstrate this
idea in a model of neutrino mass with (right-handed) singlet neutrinos and a
singlet scalar.Comment: 5 pages, no figure
Long-range order versus random-singlet phases in quantum antiferromagnetic systems with quenched disorder
The stability of antiferromagnetic long-range order against quenched disorder
is considered. A simple model of an antiferromagnet with a spatially varying
Neel temperature is shown to possess a nontrivial fixed point corresponding to
long-range order that is stable unless either the order parameter or the
spatial dimensionality exceeds a critical value. The instability of this fixed
point corresponds to the system entering a random-singlet phase. The
stabilization of long-range order is due to quantum fluctuations, whose role in
determining the phase diagram is discussed.Comment: 5 pp., REVTeX, epsf, 3 eps figs, final version as published,
including erratu
Gapless Spin-Fluid Ground State in a Random Quantum Heisenberg Magnet
We examine the spin- quantum Heisenberg magnet with Gaussian-random,
infinite-range exchange interactions. The quantum-disordered phase is accessed
by generalizing to symmetry and studying the large limit. For large
the ground state is a spin-glass, while quantum fluctuations produce a
spin-fluid state for small . The spin-fluid phase is found to be generically
gapless - the average, zero temperature, local dynamic spin-susceptibility
obeys \bar{\chi} (\omega ) \sim \log(1/|\omega|) + i (\pi/2) \mbox{sgn}
(\omega) at low frequencies. This form is identical to the phenomenological
`marginal' spectrum proposed by Varma {\em et. al.\/} for the doped cuprates.Comment: 13 pages, REVTEX, 2 figures available by request from
[email protected]
Test ideals in mixed characteristic: a unified theory up to perturbation
Let be an integral scheme of finite type over a complete DVR of mixed
characteristic. We provide a definition of a test ideal which agrees with the
multiplier ideal after inverting , can be computed from a sufficiently large
alteration, agrees with previous mixed characteristic BCM test ideals after
localizing and completing at any point of residue characteristic (up to
small perturbation), and which satisfies the full suite of expected properties
of a multiplier or test ideal. This object is obtained via the -adic
Riemann-Hilbert functor.Comment: 99 pages, comments welcom
Low Energy Properties of the Random Spin-1/2 Ferromagnetic-Antiferromagnetic Heisenberg Chain
The low energy properties of the spin-1/2 random Heisenberg chain with
ferromagnetic and antiferromagnetic interactions are studied by means of the
density matrix renormalization group (DMRG) and real space renormalization
group (RSRG) method for finite chains. The results of the two methods are
consistent with each other. The deviation of the gap distribution from that of
the random singlet phase and the formation of the large-spin state is observed
even for relatively small systems. For a small fraction of the ferromagnetic
bond, the effect of the crossover to the random singlet phase on the low
temperature susceptibility and specific heat is discussed. The crossover
concentration of the ferromagnetic bond is estimated from the numerical data.Comment: 11 pages, revtex, figures upon reques
Percolation Transition in the random antiferromagnetic spin-1 chain
We give a physical description in terms of percolation theory of the phase
transition that occurs when the disorder increases in the random
antiferromagnetic spin-1 chain between a gapless phase with topological order
and a random singlet phase. We study the statistical properties of the
percolation clusters by numerical simulations, and we compute exact exponents
characterizing the transition by a real-space renormalization group
calculation.Comment: 9 pages, 4 encapsulated Postscript figures, REVTeX 3.
Critical points and quenched disorder: From Harris criterion to rare regions and smearing
We consider the influence of quenched spatial disorder on phase transitions
in classical and quantum systems. We show that rare strong disorder
fluctuations can have dramatic effects on critical points. In classical systems
with sufficiently correlated disorder or in quantum systems with overdamped
dynamics they can completely destroy the sharp phase transition by smearing.
This is caused by effects similar to but stronger than Griffiths phenomena:
True static order can develop on a rare region while the bulk system is still
in the disordered phase. We discuss the thermodynamic behavior in the vicinity
of such a smeared transition using optimal fluctuation theory, and we present
numerical results for a two-dimensional model system.Comment: 10 pages, 5 eps figures, contribution to the Festschrift for Michael
Schreiber's 50th birthday, final version as publishe
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