6,614 research outputs found
Asymptotic base loci on singular varieties
We prove that the non-nef locus and the restricted base locus of a
pseudoeffective divisor coincide on KLT pairs. We also extend to KLT pairs F.
Russo's characterization of nef and abundant divisors by means of asymptotic
multiplier ideals.Comment: Improved exposition. To appear in "Math. Z.
The role of environmental correlations in the non-Markovian dynamics of a spin system
We put forward a framework to study the dynamics of a chain of interacting
quantum particles affected by individual or collective multi-mode environment,
focussing on the role played by the environmental quantum correlations over the
evolution of the chain. The presence of entanglement in the state of the
environmental system magnifies the non-Markovian nature of the chain's
dynamics, giving rise to structures in figures of merit such as entanglement
and purity that are not observed under a separable multi-mode environment. Our
analysis can be relevant to problems tackling the open-system dynamics of
biological complexes of strong current interest.Comment: 9 pages, 12 figure
Coexistence of different scaling laws for the entanglement entropy in a periodically driven system
The out-of-equilibrium dynamics of many body systems has recently received a
burst of interest, also due to experimental implementations. The dynamics of
both observables, such as magnetization and susceptibilities, and quantum
information related quantities, such as concurrence and entanglement entropy,
have been investigated under different protocols bringing the system out of
equilibrium. In this paper we focus on the entanglement entropy dynamics under
a sinusoidal drive of the transverse magnetic field in the 1D quantum Ising
model. We find that the area and the volume law of the entanglement entropy
coexist under periodic drive for an initial non-critical ground state.
Furthermore, starting from a critical ground state, the entanglement entropy
exhibits finite size scaling even under such a periodic drive. This
critical-like behaviour of the out-of-equilibrium driven state can persist for
arbitrarily long time, provided that the entanglement entropy is evaluated on
increasingly subsystem sizes, whereas for smaller sizes a volume law holds.
Finally, we give an interpretation of the simultaneous occurrence of critical
and non-critical behaviour in terms of the propagation of Floquet
quasi-particles.Comment: contribution to the 11th Italian Quantum Information Science
conference (IQIS), September 17th-20th, 2018 - Catania, Italy, 4 page
Class of exact memory-kernel master equations
A well-known situation in which a non-Markovian dynamics of an open quantum
system arises is when this is coherently coupled to an auxiliary system
in contact with a Markovian bath. In such cases, while the joint dynamics of
- is Markovian and obeys a standard (bipartite) Lindblad-type master
equation (ME), this is in general not true for the reduced dynamics of .
Furthermore, there are several instances (\eg the dissipative Jaynes-Cummings
model) in which a {\it closed} ME for the 's state {\it cannot} even be
worked out. Here, we find a class of bipartite Lindblad-type MEs such that the
reduced ME of can be derived exactly and in a closed form for any initial
product state of -. We provide a detailed microscopic derivation of our
result in terms of a mapping between two collision modelsComment: 9 pages, 1 figur
Composite quantum collision models
A collision model (CM) is a framework to describe open quantum dynamics. In
its {\it memoryless} version, it models the reservoir as
consisting of a large collection of elementary ancillas: the dynamics of the
open system results from successive "collisions" of
with the ancillas of . Here, we present a general formulation of
memoryless {\it composite} CMs, where is partitioned into the very
open system under study coupled to one or more auxiliary systems .
Their composite dynamics occurs through internal - collisions
interspersed with external ones involving and the reservoir . We show that important known instances of quantum {\it non-Markovian}
dynamics of -- such as the emission of an atom into a reservoir featuring a
Lorentzian, or multi-Lorentzian, spectral density or a qubit subject to random
telegraph noise -- can be mapped on to such {\it memoryless} composite CMs.Comment: 12 pages, 4 figure
Plasma properties from the multi-wavelength analysis of the November 1st 2003 CME/shock event
The analysis of the spectral properties and dynamic evolution of a CME/shock
event observed on November 1st 2003 in white-light by the LASCO coronagraph and
in the ultraviolet by the UVCS instrument operating aboard SOHO, has been
performed to compute the properties of some important plasma parameters in the
middle corona below about 2 solar radii. Simultaneous observations obtained
with the MLSO/Mk4 white-light coronagraph, providing both the early evolution
of the CME expansion in the corona and the pre-shock electron density profile
along the CME front, were also used to study this event. By combining the above
information with the analysis of the metric type II radio emission detected by
ground-based radio spectrographs, we finally derive estimates of the values of
the local Alfv\'en speed and magnetic field strength in the solar corona.Comment: In press Journal of Advanced Research, Cairo University. Production
and hosting by Elsevier B.
Tuning non-Markovianity by spin-dynamics control
We study the interplay between forgetful and memory-keeping evolution
enforced on a two-level system by a multi-spin environment whose elements are
coupled to local bosonic baths. Contrarily to the expectation that any
non-Markovian effect would be buried by the forgetful mechanism induced by the
spin-bath coupling, one can actually induce a full Markovian-to-non-Markovian
transition of the two-level system's dynamics, controllable by parameters such
as the mismatch between the energy of the two-level system and of the spin
environment. For a symmetric coupling, the amount of non-Markovianity
surprisingly grows with the number of decoherence channels.Comment: 7 pages, 6 figures, PRA versio
Galectin genes: regulation of expression.
In this review we have summarized the more recent studies on the expression of mammalian galectins. One interesting observation that can be made is that in most of microarrays and/or differential display analysis performed in recent years one or more galectins have been picked up. From a critical evaluation of the pertinent studies the main conclusion that can be drawn is that, although it is not yet clear whether the 14 galectins identified so far have functions in common, a striking common feature of all galectins is the strong modulation of their expression during development, differentiation stages and under different physiological or pathological conditions. This suggests that the expression of different galectins is finely tuned and possibly coordinated. In spite of these observations it is rather unexpected that very few studies have been performed on the molecular mechanisms governing the activity of galectin genes
Quantum non-Markovian piecewise dynamics from collision models
Recently, a large class of quantum non-Markovian piecewise dynamics for an
open quantum system obeying closed evolution equations has been introduced [B.
Vacchini, Phys. Rev. Lett. 117, 230401 (2016)]. These dynamics have been
defined in terms of a waiting-time distribution between quantum jumps, along
with quantum maps describing the effect of jumps and the system's evolution
between them. Here, we present a quantum collision model with memory, whose
reduced dynamics in the continuous-time limit reproduces the above class of
non-Markovian piecewise dynamics, thus providing an explicit microscopic
realization.Comment: 18 pages, 1 figures. Submitted to "Open Systems and Information
Dynamics" as a contribution to the upcoming special issue titled "40 years of
the GKLS equation
An optimization procedure based on thermal discomfort minimization to support the design of comfortable Net Zero Energy Buildings
The European standard EN 15251 specifies design criteria for dimensioning of building systems. In detail, it proposes that the adaptive comfort model is used, at first, for dimensioning passive means; but, if indoor operative temperature does not meet the chosen long-term adaptive comfort criterion in the “cooling season”, the design would include a mechanical cooling system. In this case, the reference design criteria are provided accordingly the Fanger comfort model. However, there is a discontinuity by switching from the adaptive to the Fanger model, since the best building variant, according to the former, may not coincide with the optimal according to the latter.
In this paper, an optimization procedure to support the design of a comfort-optimized net zero energy building is proposed. It uses an optimization engine (GenOpt) for driving a dynamic simulation engine (EnergyPlus) towards those building variants that minimize, at first, two seasonal long-term discomfort indices based on an adaptive model; and if indoor conditions do not meet the adaptive comfort limits or analyst’s expectations, it minimizes two seasonal long-term discomfort indices based on the Fanger model. The calculation of such indices has been introduced in EnergyPlus via the Energy Management System module, by writing computer codes in the EnergyPlus Reference Language.
The used long-term discomfort indices proved to provide similar ranking capabilities of building variants, even if they are based on different comfort models, and the proposed procedure meets the two- step procedure suggested by EN 15251 without generating significant discontinuities
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