1,171 research outputs found
Mott Transition and Magnetism in Rare Earth Nickelates and its Fingerprint on the X-ray Scattering
The metal-insulator transition (MIT) remains among the most thoroughly
studied phenomena in solid state physics, but the complexity of the phenomena,
which usually involves cooperation of many degrees of freedom including
orbitals, fluctuating local moments, magnetism, and the crystal structure, have
resisted predictive ab-initio treatment. Here we develop ab-initio theoretical
method for correlated electron materials, based on Dynamical Mean Field Theory,
which can predict the change of the crystal structure across the MIT at finite
temperature. This allows us to study the coupling between electronic, magnetic
and orbital degrees of freedom with the crystal structure across the MIT in
rare-earth nickelates. We predict the free energy profile of the competing
states, and the theoretical magnetic ground state configuration, which is in
agreement with neutron scattering data, but is different from the magnetic
models proposed before. The resonant elastic X-ray response at the K-edge,
which was argued to be a direct probe of the charge order, is theoretically
modelled within the Dynamical Mean Field Theory, including the core-hole
interaction. We show that the line-shape of the measured resonant elastic X-ray
response can be explained with the "site-selective" Mott scenario without real
charge order on Ni sites.Comment: Acknowledgments updated, citations adde
Getting Somewhere: People v. Turner (2016) and the Efficacy of Survivor Narratives
An examination of the narrative and rhetorical techniques employed in survivor narratives, and how these have been necessitated by legal biases and unjust social and cultural practices
Independent electrons model for open quantum systems: Landauer-Buettiker formula and strict positivity of the entropy production
A general argument leading from the formula for currents through an open
noninteracting mesoscopic system given by the theory of non-equilibrium steady
states (NESS) to the Landauer-Buettiker formula is pointed out. Time reversal
symmetry is not assumed. As a consequence it follows that, as far as the system
has a nontrivial scattering theory and the reservoirs have different
temperatures and/or chemical potentials, the entropy production is strictly
positive.Comment: 12 pages. Submitted for publication in J. Math. Phys. on 2006-06-05.
Revision and extension of: G. Nenciu, A general proof of Landauer-Buettiker
formula, [math-ph/0603030
New Solutions to the Firing Squad Synchronization Problems for Neural and Hyperdag P Systems
We propose two uniform solutions to an open question: the Firing Squad
Synchronization Problem (FSSP), for hyperdag and symmetric neural P systems,
with anonymous cells. Our solutions take e_c+5 and 6e_c+7 steps, respectively,
where e_c is the eccentricity of the commander cell of the dag or digraph
underlying these P systems. The first and fast solution is based on a novel
proposal, which dynamically extends P systems with mobile channels. The second
solution is substantially longer, but is solely based on classical rules and
static channels. In contrast to the previous solutions, which work for
tree-based P systems, our solutions synchronize to any subset of the underlying
digraph; and do not require membrane polarizations or conditional rules, but
require states, as typically used in hyperdag and neural P systems
Graph-Controlled Insertion-Deletion Systems
In this article, we consider the operations of insertion and deletion working
in a graph-controlled manner. We show that like in the case of context-free
productions, the computational power is strictly increased when using a control
graph: computational completeness can be obtained by systems with insertion or
deletion rules involving at most two symbols in a contextual or in a
context-free manner and with the control graph having only four nodes.Comment: In Proceedings DCFS 2010, arXiv:1008.127
Design Patterns for Efficient Solutions to NP-Complete Problems in Membrane Computing
Many variants of P systems have the ability to generate an
exponential number of membranes in linear time. This feature has been
exploited to elaborate (theoretical) efficient solutions to NP-complete, or
even harder, problems. A thorough review of the existent solutions shows
the utilization of common techniques and procedures. The abstraction
of the latter into design patterns can serve to ease and accelerate the
construction of efficient solutions to new hard problems.Ministerio de Economía y Competitividad TIN2017-89842-
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