22,995 research outputs found
Evolution of complexity following a quantum quench in free field theory
Using a recent proposal of circuit complexity in quantum field theories
introduced by Jefferson and Myers, we compute the time evolution of the
complexity following a smooth mass quench characterized by a time scale in a free scalar field theory. We show that the dynamics has two distinct
phases, namely an early regime of approximately linear evolution followed by a
saturation phase characterized by oscillations around a mean value. The
behavior is similar to previous conjectures for the complexity growth in
chaotic and holographic systems, although here we have found that the
complexity may grow or decrease depending on whether the quench increases or
decreases the mass, and also that the time scale for saturation of the
complexity is of order (not parametrically larger).Comment: V2: added references, new plots, and improved discussion of results
on Section 5, V3: Few minor corrections. Published versio
Momentum-space entanglement after smooth quenches
We compute the total amount of entanglement produced between momentum modes
at late times after a smooth mass quench in free bosonic and fermionic quantum
field theories. The entanglement and R\'enyi entropies are obtained in closed
form as a function of the parameters characterizing the quench protocol. For
bosons, we show that the entanglement production is more significant for light
modes and for fast quenches. In particular, infinitely slow or adiabatic
quenches do not produce any entanglement. Depending on the quench profile, the
decrease as a function of the quench rate can be either monotonic or
oscillating. In the fermionic case the situation is subtle and there is a
critical value for the quench amplitude above which this behavior is changed
and the entropies become peaked at intermediate values of momentum and of the
quench rate. We also show that the results agree with the predictions of a
Generalized Gibbs Ensemble and obtain explicitly its parameters in terms of the
quench data.Comment: 24 pages, 8 Figures; V2 matches published versio
Kinetic Monte Carlo simulation of the nitridation of the GaAs (100) surfaces
We present, in this work, our preliminary results of a systematic theoretical
study of the adsorption of N over As-terminated GaAs (100) (21)
surfaces. We analyzed the changes in the bond-lenghts, bond-angles and the
energetics involved before and after deposition. Our results show that the
N-atoms will prefer the unoccupied sites of the surface, close to the As dimer.
The presence of the N pushes the As dimer out of the surface, leading to the
anion exchange between the N and As atoms. Based on our results, we discussed
about the kinetics of the N islands formation during epitaxial growth of the
III-Nitrides.Comment: 4 pages, 7 figures, accepted for publication in Braz. J. Phys.,
special number, Proceedings of BWSP-12, 12th Brazilian Workshop on
Semiconductor Physic
Diary of the Proceedings of an Embassy to Burma in 1760 by Captain Walter Alves, edited by Michael Charney
The following account is derived from Alexander Dalrymple, Oriental Repertory, 1808: I.351-393. Dalrymple has left us the following succinct introduction to the account below --Capt. Alves was sent back to Burma in 1760; and on his return to Bengal, transmitted to Governor Pigot, at Madrass, the following Diary of his Proceedings--the account has been edited for the SBBR by Michael Charney
Ab initio calculation of the dynamical properties of PPP and PPV
In this work, we have calculated the vibrational modes and frequencies of the
crystalline PPP (in both the Pbam and Pnnm symmetries) and PPV (in the P21/c
symmetry). Our results are in good agreement with the available experimental
data. Also, we have calculated the temperature dependence of their specific
heats at constant volume, and of their vibrational entropies. Based on our
results, at high temperatures, the PPP is more stable in the Pnnm structure
than in the Pbam one.Comment: 5 pages, 7 figures, accepted for publication in Braz. J. Phys.,
special number, Proceedings of BWSP-12, 12th Brazilian Workshop on
Semiconductor Physic
Knotted solutions, from electromagnetism to fluid dynamics
Knotted solutions to electromagnetism and fluid dynamics are investigated,
based on relations we find between the two subjects. We can write fluid
dynamics in electromagnetism language, but only on an initial surface, or for
linear perturbations, and we use this map to find knotted fluid solutions, as
well as new electromagnetic solutions. We find that knotted solutions of
Maxwell electromagnetism are also solutions of more general nonlinear theories,
like Born-Infeld, and including ones which contain quantum corrections from
couplings with other modes, like Euler-Heisenberg and string theory DBI. Null
configurations in electromagnetism can be described as a null pressureless
fluid, and from this map we can find null fluid knotted solutions. A type of
nonrelativistic reduction of the relativistic fluid equations is described,
which allows us to find also solutions of the (nonrelativistic) Euler's
equations.Comment: 36 pages, 3 figure
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