12,446 research outputs found
General Non-Markovian structure of Gaussian Master and Stochastic Schr\"odinger Equations
General open quantum systems display memory features, their master equations
are non-Markovian. We show that the subclass of Gaussian non-Markovian open
system dynamics is tractable in a depth similar to the Markovian class. The
structure of master equations exhibits a transparent generalization of the
Lindblad structure. We find and parametrize the class of stochastic
Schr\"odinger equations that unravel a given master equation, such class was
before known for Markovian systems only. We show that particular non-Markovian
unravellings known in the literature are special cases of our class
Dissipative extension of the Ghirardi-Rimini-Weber model
In this paper we present an extension of the Ghirardi-Rimini-Weber model for
the spontaneous collapse of the wavefunction. Through the inclusion of
dissipation, we avoid the divergence of the energy on the long time scale,
which affects the original model. In particular, we define new jump operators,
which depend on the momentum of the system and lead to an exponential
relaxation of the energy to a finite value. The finite asymptotic energy is
naturally associated to a collapse noise with a finite temperature, which is a
basic realistic feature of our extended model. Remarkably, even in the presence
of a low temperature noise, the collapse model is effective. The action of the
new jump operators still localizes the wavefunction and the relevance of the
localization increases with the size of the system, according to the so-called
amplification mechanism, which guarantees a unified description of the
evolution of microscopic and macroscopic systems. We study in detail the
features of our model, both at the level of the trajectories in the Hilbert
space and at the level of the master equation for the average state of the
system. In addition, we show that the dissipative Ghirardi-Rimini-Weber model,
as well as the original one, can be fully characterized in a compact way by
means of a proper stochastic differential equation.Comment: 25 pages, 2 figures; v2: close to the published versio
Service Learning in Undergraduate Nursing Education: Strategies to Facilitate Meaningful Reflection
Service learning is recognized as a valuable pedagogy involving experiential learning, reflection, and reciprocal learning. Students develop critical thinking and social awareness by using the crucial activity of reflecting upon their experiential learning with community partners. The purpose of this paper is to demystify the process of reflection by identifying best practices to enhance reflection and offering suggestions for grading. By understanding “the what” and “the how” of reflection, educators can implement service learning experiences designed to include the essential component of reflection. Strategies for facilitating meaningful reflection are described including descriptions of what students should reflect upon and how to initiate reflection through writing, reading, doing, and telling. Grading rubrics are suggested to facilitate evaluation of student reflection. When properly implemented, service learning encourages students to be good citizens of the world. By using best practices associated with reflection, students can be challenged to think critically about the world and how their service can achieve community goals
Can a spontaneous collapse in flavour oscillations be tested at KLOE?
Why do we never see a table in a superposition of here and there? This
problem gets a solution by so called collapse models assuming the collapse as a
genuinely physical process. Here we consider two specific collapse models and
apply them to systems at high energies, i.e. flavour oscillating neutral meson
systems. We find on one hand a potentially new interpretation of the decay
rates introduced by hand in the standard formalism and on the other hand that
these systems at high energies constrain by experimental data the possible
collapse scenarios.Comment: To appear in the proceedings of the KLOE-2 Workshop on e+e- collision
physics at 1 GeV, 26-28 October 2016, INFN - Laboratori Nazionali di
Frascati, Ital
Coexistence between fluid and crystalline phases of proteins in photosynthetic membranes
Photosystem II (PSII) and its associated light-harvesting complex II (LHCII)
are highly concentrated in the stacked grana regions of photosynthetic
thylakoid membranes. Within the membrane, PSII-LHCII supercomplexes can be
arranged in disordered packings, ordered arrays, or mixtures thereof. The
physical driving forces underlying array formation are unknown, complicating
attempts to determine a possible functional role for arrays in regulating light
harvesting or energy conversion efficiency. Here we introduce a coarse-grained
model of protein interactions in coupled photosynthetic membranes, focusing on
just two particle types that feature simple shapes and potential energies
motivated by structural studies. Reporting on computer simulations of the
model's equilibrium fluctuations, we demonstrate its success in reproducing
diverse structural features observed in experiments, including extended
PSII-LHCII arrays. Free energy calculations reveal that the appearance of
arrays marks a phase transition from the disordered fluid state to a
system-spanning crystal, which can easily be arrested by thermodynamic
constraints or slow dynamics. The region of fluid-crystal coexistence is broad,
encompassing much of the physiologically relevant parameter regime. Our results
suggest that grana membranes lie at or near phase coexistence, conferring
significant structural and functional flexibility to this densely packed
membrane protein system.Comment: 11 pages, 5 figure
Holgraphy and BMS field theory
We study the key ingredients of a candidate holographic correspondence in an
asymptotically flat spacetimes; in particular we develop the kinematical and
the classical dynamical data of a BMS invariant field theory living at null
infinity.Comment: 3 pages, to appear in the Proceedings for the ``XVI SIGRAV
Conference'' in Vietri sul Mare (SA) 13-16 Septembe
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