1,003 research outputs found
Sub-ballistic growth of R\'enyi entropies due to diffusion
We investigate the dynamics of quantum entanglement after a global quench and
uncover a qualitative difference between the behavior of the von Neumann
entropy and higher R\'enyi entropies. We argue that the latter generically grow
\emph{sub-ballistically}, as , in systems with diffusive
transport. We provide strong evidence for this in both a U symmetric
random circuit model and in a paradigmatic non-integrable spin chain, where
energy is the sole conserved quantity. We interpret our results as a
consequence of local quantum fluctuations in conserved densities, whose
behavior is controlled by diffusion, and use the random circuit model to derive
an effective description. We also discuss the late-time behavior of the second
R\'enyi entropy and show that it exhibits hydrodynamic tails with \emph{three
distinct power laws} occurring for different classes of initial states.Comment: close to published version: 4 + epsilon pages, 3 figures + supplemen
Diffusive hydrodynamics of out-of-time-ordered correlators with charge conservation
The scrambling of quantum information in closed many-body systems, as
measured by out-of-time-ordered correlation functions (OTOCs), has lately
received considerable attention. Recently, a hydrodynamical description of
OTOCs has emerged from considering random local circuits, aspects of which are
conjectured to be universal to ergodic many-body systems, even without
randomness. Here we extend this approach to systems with locally conserved
quantities (e.g., energy). We do this by considering local random unitary
circuits with a conserved U charge and argue, with numerical and
analytical evidence, that the presence of a conservation law slows relaxation
in both time ordered {\textit{and}} out-of-time-ordered correlation functions,
both can have a diffusively relaxing component or "hydrodynamic tail" at late
times. We verify the presence of such tails also in a deterministic,
peridocially driven system. We show that for OTOCs, the combination of
diffusive and ballistic components leads to a wave front with a specific,
asymmetric shape, decaying as a power law behind the front. These results also
explain existing numerical investigations in non-noisy ergodic systems with
energy conservation. Moreover, we consider OTOCs in Gibbs states, parametrized
by a chemical potential , and apply perturbative arguments to show that
for the ballistic front of information-spreading can only develop at
times exponentially large in -- with the information traveling
diffusively at earlier times. We also develop a new formalism for describing
OTOCs and operator spreading, which allows us to interpret the saturation of
OTOCs as a form of thermalization on the Hilbert space of operators.Comment: Close to published version: 17 + 9.5 pages. Improved presentation.
Contains new section on clean Floquet spin chain. New and/or improved
numerical data in Figures 4-7, 11, 1
Spectral functions and optical conductivity of spinless fermions on a checkerboard lattice
We study the dynamical properties of spinless fermions on the checkerboard
lattice. Our main interest is the limit of large nearest-neighbor repulsion
as compared with hopping . The spectral functions show broad low-energy
excitation which are due to the dynamics of fractionally charged excitations.
Furthermore, it is shown that the fractional charges contribute to the
electrical current density.Comment: 9 Pages, 9 Figure
Occurrence and formation of indole-3-acetamide in Arabidopsis thaliana
An HPLC/GCâMS/MS technique (high-pressure liquid chromatography in combination with gas chromatographyâtandem mass spectrometry) has been worked out to analyze indole-3-acetamide (IAM) with very high sensitivity, using isotopically labelled IAM as an internal standard. Using this technique, the occurrence of IAM in sterile-grown Arabidopsis thaliana (L.) Heynh. was demonstrated unequivocally. In comparison, plants grown under non-sterile conditions in soil in a greenhouse showed approximately 50% higher average levels of IAM, but the differences were not statistically significant. Thus, microbial contributions to the IAM extracted from the tissue are likely to be minor. Levels of IAM in sterile-grown seedlings were highest in imbibed seeds and then sharply declined during the first 24 h of germination and further during early seedling development to remain below 20â30 pmol gâ1 fresh weight throughout the rosette stage. The decline in indole-3-aetic acid (IAA) levels during germination was paralleled by a similar decline in IAM levels. Recombinant nitrilase isoforms 1, 2 and 3, known to synthesize IAA from indole-3-acetonitrile, were shown to produce significant amounts of IAM in vitro as a second end product of the reaction besides IAA. NIT2 was earlier shown to be highly expressed in developing and in mature A. thaliana embryos, and NIT3 is the dominantly active gene in the hypocotyl and the cotyledons of young, germinating seedlings. Collectively, these data suggest that the elevated levels of IAM in seeds and germinating seedlings result from nitrilase action on indole-3-acetonitrile, a metabolite produced in the plants presumably from glucobrassicin turnover
The Misprediction of emotions in Track Athletics.: Is experience the teacher of all things?
People commonly overestimate the intensity of their emotions toward future events. In other words, they display an impact bias. This research addresses the question whether people learn from their experiences and correct for the impact bias. We hypothesize that athletes display an impact bias and, counterintuitively, that increased experience with an event increases this impact bias. A field study in the context of competitive track athletics supported our hypotheses by showing that athletes clearly overestimated their emotions toward the outcome of a track event and that this impact bias was more pronounced for negative events than for positive events. Moreover, with increased athletic experience this impact bias became larger. This effect could not be explained by athletesâ forecasted emotions, but it could be explained by the emotions they actually felt following the race. The more experience athletes had with athletics, the less they felt negative emotions after unsuccessful goal attainment. These findings are discussed in relation to possible underlying emotion regulation processes
The Agrobacterium vitis T-6b oncoprotein induces auxin-independent cell expansion in tobacco
Among the Agrobacterium T-DNA genes, rolB, rolC, orf13, orf8, lso, 6b and several other genes encode weakly homologous proteins with remarkable effects on plant growth. The 6b oncogene induces tumors and enations. In order to study its properties we have used transgenic tobacco plants that carry a dexamethasone-inducible 6b gene, dex-T-6b. Upon induction, dex-T-6b plants develop a large array of morphological modifications, some of which involve abnormal cell expansion. In the present investigation, dex-T-6b-induced expansion was studied in intact leaves and an in vitro leaf disc system. Although T-6b and indole-3-acetic acid (IAA) both induced expansion and were non-additive, T-6b expression did not increase IAA levels, nor did it induce an IAA-responsive gene. Fusicoccin (FC) is known to stimulate expansion by increasing cell wall plasticity. T-6b- and FC-induced expansion were additive at saturating FC concentrations, indicating that T-6b does not act by a similar mechanism to FC. T-6b expression led to higher leaf osmolality values, in contrast to FC, suggesting that the T-6b gene induces expansion by increasing osmolyte concentrations. Metabolite profiling showed that glucose and fructose played a major role in this increase. We infer that T-6b disrupts the osmoregulatory controls that govern cell expansion during development and wound healing
Spectral functions for strongly correlated 5f-electrons
We calculate the spectral functions of model systems describing 5f-compounds
adopting Cluster Perturbation Theory. The method allows for an accurate
treatment of the short-range correlations. The calculated excitation spectra
exhibit coherent 5f bands coexisting with features associated with local
intra-atomic transitions. The findings provide a microscopic basis for partial
localization. Results are presented for linear chains.Comment: 10 Page
Stability of the thermohaline circulation examined with a one-dimensional fluid loop
The Stommel box model elegantly demonstrates that the oceanic response to mixed boundary conditions, combining a temperature relaxation with a fixed salt flux forcing, is nonlinear owing to the so-called salt advection feedback. This nonlinearity produces a parameter range of bi-stability associated with hysteresis effects characterised by a fast thermally-driven mode and a slow salinity-driven mode. Here we investigate whether a similar dynamical behaviour can be found in the thermohaline loop model, a one-dimensional analogue of the box model. A semi-analytical method to compute possible steady states of the loop model is presented, followed by a linear stability analysis carried out for a large range of loop configurations. While the salt advection feedback is found as in the box model, a major difference is obtained for the fast mode: an oscillatory instability is observed near the turning point of the fast mode branch, such that the range of bi-stability is systematically reduced, or even removed, in some cases. The oscillatory instability originates from a salinity anomaly that grows exponentially as it turns around the loop, a situation that may occur only when the salinity torque is directed against the loop flow. Factors such as mixing intensity, the relative strength of thermal and haline forcings, the nonlinearity of the equation of state or the loop geometry can strongly affect the stability properties of the loop
A Time Series of BV photometry and Halpha Emission Fluxes of the Eclipsing Binary VV Cep
VV Cephei (= HR 8383 = HD 208816) is the brightest eclipsing M supergiant binary (M2 Iab + B0-2? V) in the sky, and is a massive binary with one of the
longest known orbital periods (7430 days = 20.34 years) of any eclipsing system. With the next eclipse beginning in August 2017, and lasting nearly
two years (650 days) from 1st to 4th contact, an extensive observational campaign is planned. This paper focusses on the photometric variability
of the system out of eclipse, and presents and photometry and H emission fluxes observed over the period from mid-2008 through
late 2016. The and light curves show correlated variability with peak power of 145 days, presumably due to low-amplitude pulsations of
the M supergiant. The H emission fluxes show a short-term variability, but the sampling is not sufficient to permit quantitative analysis.
However, the H fluxes also appear to show a long-term modulation related to the variable orbital separation of this eccentric binary
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