49 research outputs found
Density dynamics from current auto-correlations at finite time- and length-scales
We consider the increase of the spatial variance of some inhomogeneous,
non-equilibrium density (particles, energy, etc.) in a periodic quantum system
of condensed matter-type. This is done for a certain class of initial quantum
states which is supported by static linear response and typicality arguments.
We directly relate the broadening to some current auto-correlation function at
finite times. Our result is not limited to diffusive behavior, however, in that
case it yields a generalized Einstein relation. These findings facilitate the
approximation of diffusion constants/conductivities on the basis of current
auto-correlation functions at finite times for finite systems. Pursuing this,
we quantitatively confirm the magnetization diffusion constant in a spin chain
which was recently found from non-equilibrium bath scenarios.Comment: 4 pages, 1 figure, accepted for publication in Europhys. Let
Third quantization: a general method to solve master equations for quadratic open Fermi systems
The Lindblad master equation for an arbitrary quadratic system of n fermions
is solved explicitly in terms of diagonalization of a 4n x 4n matrix, provided
that all Lindblad bath operators are linear in the fermionic variables. The
method is applied to the explicit construction of non-equilibrium steady states
and the calculation of asymptotic relaxation rates in the far from equilibrium
problem of heat and spin transport in a nearest neighbor Heisenberg XY spin 1/2
chain in a transverse magnetic field.Comment: 24 pages, with 8 eps figures - few minor corrections to the published
version, e.g. anti-symmetrizing the matrix given by eq. (27
Holographic View on Quantum Correlations and Mutual Information between Disjoint Blocks of a Quantum Critical System
In (d+1) dimensional Multiscale Entanglement Renormalization Ansatz (MERA)
networks, tensors are connected so as to reproduce the discrete, (d + 2)
holographic geometry of Anti de Sitter space (AdSd+2) with the original system
lying at the boundary. We analyze the MERA renormalization flow that arises
when computing the quantum correlations between two disjoint blocks of a
quantum critical system, to show that the structure of the causal cones
characteristic of MERA, requires a transition between two different regimes
attainable by changing the ratio between the size and the separation of the two
disjoint blocks. We argue that this transition in the MERA causal developments
of the blocks may be easily accounted by an AdSd+2 black hole geometry when the
mutual information is computed using the Ryu-Takayanagi formula. As an explicit
example, we use a BTZ AdS3 black hole to compute the MI and the quantum
correlations between two disjoint intervals of a one dimensional boundary
critical system. Our results for this low dimensional system not only show the
existence of a phase transition emerging when the conformal four point ratio
reaches a critical value but also provide an intuitive entropic argument
accounting for the source of this instability. We discuss the robustness of
this transition when finite temperature and finite size effects are taken into
account.Comment: 21 pages, 5 figures. Abstract and Figure 1 has been modified. Minor
modifications in Section 1 and Section
Creation and manipulation of entanglement in spin chains far from equilibrium
We investigate creation, manipulation, and steering of entanglement in spin
chains from the viewpoint of quantum communication between distant parties. We
demonstrate how global parametric driving of the spin-spin coupling and/or
local time-dependent Zeeman fields produce a large amount of entanglement
between the first and the last spin of the chain. This occurs whenever the
driving frequency meets a resonance condition, identified as "entanglement
resonance". Our approach marks a promising step towards an efficient quantum
state transfer or teleportation in solid state system. Following the reasoning
of Zueco et al. [1], we propose generation and routing of multipartite
entangled states by use of symmetric tree-like structures of spin chains.
Furthermore, we study the effect of decoherence on the resulting spin
entanglement between the corresponding terminal spins.Comment: 10 pages, 8 figure
Gender and sustainable livelihoods: linking gendered experiences of environment, community and self
In this essay I explore the economic, social,
environmental and cultural changes taking place in Bolsena,
Italy, where agricultural livelihoods have rapidly
diminished in the last two decades. I examine how gender
dynamics have shifted with the changing values and
livelihoods of Bolsena through three women’s narratives
detailing their gendered experiences of environment,
community and self. I reflect on these changes with Sabrina,
who is engaged in a feminist community-based
organization; Anna, who is running an alternative wine bar;
and Isabella, a jeweler, who is engaged in ecofeminist
practices. My analysis is based on concepts developed by
feminist political ecology: specifically, the theory of rooted
networks from Dianne Rocheleau, Donna Haraway’s concept
of naturecultures (and the work of J. K. Gibson-Graham
on new economic imaginaries emerging from the
politics of place. I aim to think with, reflect upon and
provoke from the ‘‘otherwise’’, taking into account the
lived relations entwining nature and gender. My article
looks at the interconnections of gender, environment and
livelihoods, attentive to the daily needs, embodied interactions
and labours of these three women as part of a
reappropriation, reconstruction and reinvention of Bolsena’s
lifeworld. By listening to the stories of their everyday
lives and struggles, I show the dynamic potential of the
politics of place and the efforts to build diverse economies
and more ethical economic and ecological relationships
based on gender-aware subjectivities and values
From thermal rectifiers to thermoelectric devices
We discuss thermal rectification and thermoelectric energy conversion from
the perspective of nonequilibrium statistical mechanics and dynamical systems
theory. After preliminary considerations on the dynamical foundations of the
phenomenological Fourier law in classical and quantum mechanics, we illustrate
ways to control the phononic heat flow and design thermal diodes. Finally, we
consider the coupled transport of heat and charge and discuss several general
mechanisms for optimizing the figure of merit of thermoelectric efficiency.Comment: 42 pages, 22 figures, review paper, to appear in the Springer Lecture
Notes in Physics volume "Thermal transport in low dimensions: from
statistical physics to nanoscale heat transfer" (S. Lepri ed.
Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease
Background: Experimental and clinical data suggest that reducing inflammation without affecting lipid levels may reduce the risk of cardiovascular disease. Yet, the inflammatory hypothesis of atherothrombosis has remained unproved. Methods: We conducted a randomized, double-blind trial of canakinumab, a therapeutic monoclonal antibody targeting interleukin-1β, involving 10,061 patients with previous myocardial infarction and a high-sensitivity C-reactive protein level of 2 mg or more per liter. The trial compared three doses of canakinumab (50 mg, 150 mg, and 300 mg, administered subcutaneously every 3 months) with placebo. The primary efficacy end point was nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. RESULTS: At 48 months, the median reduction from baseline in the high-sensitivity C-reactive protein level was 26 percentage points greater in the group that received the 50-mg dose of canakinumab, 37 percentage points greater in the 150-mg group, and 41 percentage points greater in the 300-mg group than in the placebo group. Canakinumab did not reduce lipid levels from baseline. At a median follow-up of 3.7 years, the incidence rate for the primary end point was 4.50 events per 100 person-years in the placebo group, 4.11 events per 100 person-years in the 50-mg group, 3.86 events per 100 person-years in the 150-mg group, and 3.90 events per 100 person-years in the 300-mg group. The hazard ratios as compared with placebo were as follows: in the 50-mg group, 0.93 (95% confidence interval [CI], 0.80 to 1.07; P = 0.30); in the 150-mg group, 0.85 (95% CI, 0.74 to 0.98; P = 0.021); and in the 300-mg group, 0.86 (95% CI, 0.75 to 0.99; P = 0.031). The 150-mg dose, but not the other doses, met the prespecified multiplicity-adjusted threshold for statistical significance for the primary end point and the secondary end point that additionally included hospitalization for unstable angina that led to urgent revascularization (hazard ratio vs. placebo, 0.83; 95% CI, 0.73 to 0.95; P = 0.005). Canakinumab was associated with a higher incidence of fatal infection than was placebo. There was no significant difference in all-cause mortality (hazard ratio for all canakinumab doses vs. placebo, 0.94; 95% CI, 0.83 to 1.06; P = 0.31). Conclusions: Antiinflammatory therapy targeting the interleukin-1β innate immunity pathway with canakinumab at a dose of 150 mg every 3 months led to a significantly lower rate of recurrent cardiovascular events than placebo, independent of lipid-level lowering. (Funded by Novartis; CANTOS ClinicalTrials.gov number, NCT01327846.