535 research outputs found
Does the Boltzmann principle need a dynamical correction?
In an attempt to derive thermodynamics from classical mechanics, an
approximate expression for the equilibrium temperature of a finite system has
been derived [M. Bianucci, R. Mannella, B. J. West, and P. Grigolini, Phys.
Rev. E 51, 3002 (1995)] which differs from the one that follows from the
Boltzmann principle S = k log (Omega(E)) via the thermodynamic relation 1/T=
dS/dE by additional terms of "dynamical" character, which are argued to correct
and generalize the Boltzmann principle for small systems (here Omega(E) is the
area of the constant-energy surface). In the present work, the underlying
definition of temperature in the Fokker-Planck formalism of Bianucci et al. is
investigated and shown to coincide with an approximate form of the
equipartition temperature. Its exact form, however, is strictly related to the
"volume" entropy S = k log (Phi(E)) via the thermodynamic relation above for
systems of any number of degrees of freedom (Phi(E) is the phase space volume
enclosed by the constant-energy surface). This observation explains and
clarifies the numerical results of Bianucci et al. and shows that a dynamical
correction for either the temperature or the entropy is unnecessary, at least
within the class of systems considered by those authors. Explicit analytical
and numerical results for a particle coupled to a small chain (N~10) of quartic
oscillators are also provided to further illustrate these facts.Comment: REVTeX 4, 10 pages, 2 figures. Accepted to J. Stat. Phy
Jarzynski Equality for an Energy-Controlled System
The Jarzynski equality (JE) is known as an exact identity for nonequillibrium
systems. The JE was originally formulated for isolated and isothermal systems,
while Adib reported an JE extended to an isoenergetic process. In this paper,
we extend the JE to an energy-controlled system. We make it possible to control
the instantaneous value of the energy arbitrarily in a nonequilibrium process.
Under our extension, the new JE is more practical and useful to calculate the
number of states and the entropy than the isoenergetic one. We also show
application of our JE to a kind of optimization problems.Comment: 6 pages, 1 figur
Zero-Shot Generalizable End-to-End Task-Oriented Dialog System using Context Summarization and Domain Schema
Task-oriented dialog systems empower users to accomplish their goals by
facilitating intuitive and expressive natural language interactions.
State-of-the-art approaches in task-oriented dialog systems formulate the
problem as a conditional sequence generation task and fine-tune pre-trained
causal language models in the supervised setting. This requires labeled
training data for each new domain or task, and acquiring such data is
prohibitively laborious and expensive, thus making it a bottleneck for scaling
systems to a wide range of domains. To overcome this challenge, we introduce a
novel Zero-Shot generalizable end-to-end Task-oriented Dialog system, ZS-ToD,
that leverages domain schemas to allow for robust generalization to unseen
domains and exploits effective summarization of the dialog history. We employ
GPT-2 as a backbone model and introduce a two-step training process where the
goal of the first step is to learn the general structure of the dialog data and
the second step optimizes the response generation as well as intermediate
outputs, such as dialog state and system actions. As opposed to
state-of-the-art systems that are trained to fulfill certain intents in the
given domains and memorize task-specific conversational patterns, ZS-ToD learns
generic task-completion skills by comprehending domain semantics via domain
schemas and generalizing to unseen domains seamlessly. We conduct an extensive
experimental evaluation on SGD and SGD-X datasets that span up to 20 unique
domains and ZS-ToD outperforms state-of-the-art systems on key metrics, with an
improvement of +17% on joint goal accuracy and +5 on inform. Additionally, we
present a detailed ablation study to demonstrate the effectiveness of the
proposed components and training mechanis
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Symmetry relations in chemical kinetics arising from microscopic reversibility
It is shown that the kinetics of time-reversible chemical reactions having
the same equilibrium constant but different initial conditions are closely
related to one another by a directly measurable symmetry relation analogous to
chemical detailed balance. In contrast to detailed balance, however, this
relation does not require knowledge of the elementary steps that underlie the
reaction, and remains valid in regimes where the concept of rate constants is
ill-defined, such as at very short times and in the presence of low activation
barriers. Numerical simulations of a model of isomerization in solution are
provided to illustrate the symmetry under such conditions, and potential
applications in protein folding-unfolding are pointed out.Comment: 4 pages, 1 figure, accepted to Phys Rev Let
Entropy and density of states from isoenergetic nonequilibrium processes
Two identities in statistical mechanics involving entropy differences (or
ratios of density of states) at constant energy are derived. The first provides
a nontrivial extension of the Jarzynski equality to the microcanonical ensemble
[C. Jarzynski, Phys. Rev. Lett. 78, 2690 (1997)], which can be seen as a
``fast-switching'' version of the adiabatic switching method for computing
entropies [M. Watanabe, W. P. Reinhardt, Phys. Rev. Lett. 65, 3301 (1990)]. The
second is a thermodynamic integration formula analogous to a well-known
expression for free energies, and follows after taking the quasistatic limit of
the first. Both identities can be conveniently used in conjunction with a
scaling relation (herein derived) that allows one to extrapolate measurements
taken at a single energy to a wide range of energy values. Practical aspects of
these identities in the context of numerical simulations are discussed.Comment: 5 pages, no figure
Adiabatic invariance with first integrals of motion
The construction of a microthermodynamic formalism for isolated systems based
on the concept of adiabatic invariance is an old but seldom appreciated effort
in the literature, dating back at least to P. Hertz [Ann. Phys. (Leipzig) 33,
225 (1910)]. An apparently independent extension of such formalism for systems
bearing additional first integrals of motion was recently proposed by Hans H.
Rugh [Phys. Rev. E 64, 055101 (2001)], establishing the concept of adiabatic
invariance even in such singular cases. After some remarks in connection with
the formalism pioneered by Hertz, it will be suggested that such an extension
can incidentally explain the success of a dynamical method for computing the
entropy of classical interacting fluids, at least in some potential
applications where the presence of additional first integrals cannot be
ignored.Comment: 2 pages, no figures (REVTeX 4
Tomorrow’s world: Current developments in the therapeutic use of technology for psychosis
There is now an established evidence base for the use of information and communication technology (ICT) to support mental healthcare (‘e-mental health’) for common mental health problems. Recently, there have been significant develop-ments in the therapeutic use of computers, mobile phones, gaming and virtual reality technologies for the assessment and treatment of psychosis. We provide an overview of the therapeutic use of ICT for psychosis, drawing on searches of the scientific literature and the internet and using interviews with experts in the field. We outline interventions that are already relevant to clinical practice, some that may become available in the foreseeable future and emerging challenges for their implementation
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