1,660 research outputs found
Apparent slow dynamics in the ergodic phase of a driven many-body localized system without extensive conserved quantities
We numerically study the dynamics on the ergodic side of the many-body
localization transition in a periodically driven Floquet model with no global
conservation laws. We describe and employ a numerical technique based on the
fast Walsh-Hadamard transform that allows us to perform an exact time evolution
for large systems and long times. As in models with conserved quantities (e.g.,
energy and/or particle number) we observe a slowing down of the dynamics as the
transition into the many-body localized phase is approached. More specifically,
our data is consistent with a subballistic spread of entanglement and a
stretched-exponential decay of an autocorrelation function, with their
associated exponents reflecting slow dynamics near the transition for a fixed
system size. However, with access to larger system sizes, we observe a clear
flow of the exponents towards faster dynamics and can not rule out that the
slow dynamics is a finite-size effect. Furthermore, we observe examples of
non-monotonic dependence of the exponents with time, with dynamics initially
slowing down but accelerating again at even larger times, consistent with the
slow dynamics being a crossover phenomena with a localized critical point.Comment: 9 pages, 8 figures; added details on the level statistics and the
energy absorptio
Quantum Mutual Information as a Probe for Many-Body Localization
We demonstrate that the quantum mutual information (QMI) is a useful probe to
study many-body localization (MBL). First, we focus on the detection of a
metal--insulator transition for two different models, the noninteracting
Aubry-Andr\'e-Harper model and the spinless fermionic disordered Hubbard chain.
We find that the QMI in the localized phase decays exponentially with the
distance between the regions traced out, allowing us to define a correlation
length, which converges to the localization length in the case of one particle.
Second, we show how the QMI can be used as a dynamical indicator to distinguish
an Anderson insulator phase from an MBL phase. By studying the spread of the
QMI after a global quench from a random product state, we show that the QMI
does not spread in the Anderson insulator phase but grows logarithmically in
time in the MBL phase.Comment: 4+2 pages, 5+5 figure
Many-body localization characterized from a one-particle perspective
We show that the one-particle density matrix can be used to
characterize the interaction-driven many-body localization transition in closed
fermionic systems. The natural orbitals (the eigenstates of ) are
localized in the many-body localized phase and spread out when one enters the
delocalized phase, while the occupation spectrum (the set of eigenvalues of
) reveals the distinctive Fock-space structure of the many-body
eigenstates, exhibiting a step-like discontinuity in the localized phase. The
associated one-particle occupation entropy is small in the localized phase and
large in the delocalized phase, with diverging fluctuations at the transition.
We analyze the inverse participation ratio of the natural orbitals and find
that it is independent of system size in the localized phase.Comment: 5 pages, 3 figures; v2: added two appendices and a new figure panel
in main text; v3: updated figur
Sharp entanglement thresholds in the logarithmic negativity of disjoint blocks in the transverse-field Ising chain
Entanglement has developed into an essential concept for the characterization
of phases and phase transitions in ground states of quantum many-body systems.
In this work, we use the logarithmic negativity to study the spatial
entanglement structure in the transverse-field Ising chain both in the ground
state and at nonzero temperatures. Specifically, we investigate the
entanglement between two disjoint blocks as a function of their separation,
which can be viewed as the entanglement analog of a spatial correlation
function. We find sharp entanglement thresholds at a critical distance beyond
which the logarithmic negativity vanishes exactly and thus the two blocks
become unentangled, which holds even in the presence of long-ranged quantum
correlations, i.e., at the system's quantum critical point. Using Time-Evolving
Block Decimation (TEBD), we explore this feature as a function of temperature
and size of the two blocks and present a simple model to describe our numerical
observations.Comment: 12 pages, 7 figure
The structure of an LIM-only protein 4 (LMO4) and deformed epidermal autoregulatory factor-1 (DEAF1) complex reveals a common mode of binding to LMO4
LIM-domain only protein 4 (LMO4) is a widely expressed protein with important roles in embryonic development and breast cancer. It has been reported to bind many partners, including the transcription factor Deformed epidermal autoregulatory factor-1 (DEAF1), with which LMO4 shares many biological parallels. We used yeast two-hybrid assays to show that DEAF1 binds both LIM domains of LMO4 and that DEAF1 binds the same face on LMO4 as two other LMO4-binding partners, namely LIM domain binding protein 1 (LDB1) and C-terminal binding protein interacting protein (CtIP/RBBP8). Mutagenic screening analysed by the same method, indicates that the key residues in the interaction lie in LMO4LIM2 and the N-terminal half of the LMO4-binding domain in DEAF1. We generated a stable LMO4LIM2-DEAF1 complex and determined the solution structure of that complex. Although the LMO4-binding domain from DEAF1 is intrinsically disordered, it becomes structured on binding. The structure confirms that LDB1, CtIP and DEAF1 all bind to the same face on LMO4. LMO4 appears to form a hub in protein-protein interaction networks, linking numerous pathways within cells. Competitive binding for LMO4 therefore most likely provides a level of regulation between those different pathways.SJ was funded by an Australian Postgraduate Award (education.gov.au/australian-postgraduate-awards). JPM and JMM were awarded Senior Research
Fellowships from the Australian National and Medical Research Council (www.nhmrc.gov.au). This project was funded by an Australian Research Council (www.
arc.gov.au) Discovery Project Grant (DP110104332) to JMM and LC
Evolution of Quantum Discord and its Stability in Two-Qubit NMR Systems
We investigate evolution of quantum correlations in ensembles of two-qubit
nuclear spin systems via nuclear magnetic resonance techniques. We use discord
as a measure of quantum correlations and the Werner state as an explicit
example. We first introduce different ways of measuring discord and geometric
discord in two-qubit systems and then describe the following experimental
studies: (a) We quantitatively measure discord for Werner-like states prepared
using an entangling pulse sequence. An initial thermal state with zero discord
is gradually and periodically transformed into a mixed state with maximum
discord. The experimental and simulated behavior of rise and fall of discord
agree fairly well. (b) We examine the efficiency of dynamical decoupling
sequences in preserving quantum correlations. In our experimental setup, the
dynamical decoupling sequences preserved the traceless parts of the density
matrices at high fidelity. But they could not maintain the purity of the
quantum states and so were unable to keep the discord from decaying. (c) We
observe the evolution of discord for a singlet-triplet mixed state during a
radio-frequency spin-lock. A simple relaxation model describes the evolution of
discord, and the accompanying evolution of fidelity of the long-lived singlet
state, reasonably well.Comment: 9 pages, 7 figures, Phys. Rev. A (in press
A COMPARATIVE CLINICAL STUDY TO ASSESS THE EFFICACY OF KARIMBIRUMBADI KASHAYAM AND VASAGULUCHYADI KASHAYAM IN PANDUROGA WITH SPECIAL REFERENCE TO IRON DEFICIENCY ANEMIA IN THE REPRODUCTIVE AGE GROUP OF WOMEN
This study is an attempt to clinically analyze the independent effect of Karimbirumbadi kashayam and Vasaguluchiadi kashayam in Panduroga and also compare their efficacy. Aims and Objectives: To evaluate the comparative efficacy of Karimbirumbadi kashayam and Vasaguluchyadi kashayam in Panduroga with special reference to iron deficiency anemia in the reproductive age group of women. Methodology: Among 46 registered subjects, 22 were registered in group A and 24were registered in group B. Out of which 20 subjects of A group and 20 subjects of B group completed the study. Group A was administered with 25ml of Karimbirumbadi kashayam with 40ml of luke warm water twice daily before food for 2 months and Group B was administered with 25ml of Vasaguluchyadi kashayam with 40ml of luke warm water and 10ml of Madhu as Anupana twice daily before food for 2 months. Objective and subjective parameters were analyzed using paired T test and Wilcoxon signed rank test respectively. Independent T test and Mann-Whitney U test were used to compare the parameters between the groups. Result: There was statistically significant improvement in the objective and subjective parameters (p<0.05 was observed). Conclusion: The study shows that both Karimbirumbadi kashayam and Vasaguluchyadi kashayam are effective in relieving the symptoms of Panduroga. Symptomatic relief was seen in both the group A & B, but there was no statistically significant difference between the groups in relieving these symptoms
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