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SUMMARY:Lévy Noise\, Time-Reversal Symmetry\, Nonequilibrium Stochastic T
hermodynamics\, and Bak’s Sandpile
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UID:indico-contribution-69-425@zakopane.if.uj.edu.pl
DESCRIPTION:Speakers: Martin Bier (East Carolina University)\nThe Brownian
noise in nonequilibrium systems commonly contains more outliers. In that
case the noise is best described with a Levy distribution. Many systems in
which there are fluctuations around a steady-state throughput can be mode
led as a Levy-noise-subjected particle in a parabolic potential. We consid
er an overdamped Brownian particle in a parabolic potential. If the noise
is Levy\, time-reversal symmetry for the particle's trajectory is violated
. We formulate a parameter\, r\, to express and detect this violation. Wit
h solar flare data it is shown how r can be readily obtained and next used
to obtain a good estimate of the stability index\, α\, of the underlying
noise. Self-organized-criticality\, i.e. the famous avalanching sandpiles
of Per Bak et al\, can also be modeled with a Levy-noise-subjected partic
le on a potential. Preliminary results from such an approach are shown.\n\
nhttps://zakopane.if.uj.edu.pl/event/16/contributions/425/
LOCATION:
URL:https://zakopane.if.uj.edu.pl/event/16/contributions/425/
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SUMMARY:Pre-poster session
DTSTART;VALUE=DATE-TIME:20201203T164000Z
DTEND;VALUE=DATE-TIME:20201203T170000Z
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UID:indico-contribution-69-417@zakopane.if.uj.edu.pl
DESCRIPTION:Speakers: Paweł Góra (Jagiellonian University)\nhttps://zako
pane.if.uj.edu.pl/event/16/contributions/417/
LOCATION:
URL:https://zakopane.if.uj.edu.pl/event/16/contributions/417/
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SUMMARY:Simple mathematical models for self-propelled motion on the water
surface.
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UID:indico-contribution-69-387@zakopane.if.uj.edu.pl
DESCRIPTION:Speakers: Jerzy Gorecki (ICHF PAN)\nSelf-propelled motion on t
he water surface has fascinated scientists for almost two hundred years. T
here are many solid substances\, such as camphor\, camphene\,\nand phenant
hroline\, which can develop to the water surface as a molecular layer\, ev
aporate to the air phase and continuously dissolve into the water phase. T
his surface layer decreases the water surface tension and this decrease is
local and time-dependent. Inhomogeneities in the surface concentration\,
resulting from fluctuations in release and evaporation\, can break the sy
mmetry around an object and drive its motion. The mathematical descriptio
n of the self-propelled motion is complex because it should include object
location\, generated hydrodynamic flows\, and dissipation of surface-acti
ve molecules. The simplest mathematical models consider the object positio
n together with the concentration of surface-active molecules described by
a reaction-diffusion equation in which the effective diffusion coefficien
t includes a hydrodynamic effect. However\, \nthere are many interesting
examples of systems where the motion of a self-propelled object is strongl
y coupled with generated hydrodynamic flows and in such cases\, the model
mentioned above fails. We introduce another simple mathematical model that
describes the time evolution of a self-propelled object on a liquid surfa
ce using such variables as the object location\, the surface concentration
of active molecules\, and the hydrodynamic surface flow. The model is app
lied to simulate the time evolution of a rotor composed of a polygonal pla
te with camphor pills at its corners. We have qualitatively reproduced res
ults of experiments\, in which the inversions of rotational direction unde
r periodic stop- and release- operations were investigated. The model corr
ectly describes the probability of the inversion as a function of the dura
tion of the phase when the rotor is stopped. Moreover\, the model allows u
s to introduce the rotor asymmetry unavoidable in real experiments and stu
dy its influence on the studied phenomenon. Our numerical simulations have
revealed that the probability of the inversion of rotational direction is
determined by the competition among the transport of the camphor molecule
s by the flow\, the intrinsic asymmetry of the rotor\, and the noise ampli
tude.\n\nhttps://zakopane.if.uj.edu.pl/event/16/contributions/387/
LOCATION:
URL:https://zakopane.if.uj.edu.pl/event/16/contributions/387/
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SUMMARY:Optimization and Growth in First-Passage Resetting
DTSTART;VALUE=DATE-TIME:20201203T150000Z
DTEND;VALUE=DATE-TIME:20201203T153000Z
DTSTAMP;VALUE=DATE-TIME:20220124T235913Z
UID:indico-contribution-69-366@zakopane.if.uj.edu.pl
DESCRIPTION:Speakers: Sidney Redner (Santa Fe Institute)\nWe combine reset
ting and first-passage to define "first-passage resetting”\, where a ran
dom walk is reset to a fixed position due to a first-passage event of the
walk itself. On the infinite half-line\, first-passage resetting of isotr
opic diffusion is non-stationary\, in which the number of resetting events
grows with time as $t^{1/2}$. We calculate the resulting spatial probabi
lity distribution of the particle\, and also obtain this distribution by a
path decomposition approach. In a finite interval\, we define an first-pa
ssage-resetting optimization problem that is motivated by reliability theo
ry. Here\, the goal is to operate a mechanical system close to its maximu
m capacity without experiencing too many breakdowns. When a breakdown occ
urs\, the system is reset to its minimal operating point. We define and op
timize an objective function that maximizes the reward (being close to max
imum operation) minus a penalty for each breakdown. Finally\, we study a
first-passage-driven domain growth dynamics in which its boundary recedes
by a specified amount when a diffusing particle reaches the boundary\, aft
er which resetting occurs. We find a wide range of dynamical behaviors for
the domain growth rate in the interval and the semi-infinite line.\n\nhtt
ps://zakopane.if.uj.edu.pl/event/16/contributions/366/
LOCATION:
URL:https://zakopane.if.uj.edu.pl/event/16/contributions/366/
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SUMMARY:Restart: The Physics Of Starting Anew
DTSTART;VALUE=DATE-TIME:20201203T153000Z
DTEND;VALUE=DATE-TIME:20201203T160000Z
DTSTAMP;VALUE=DATE-TIME:20220124T235913Z
UID:indico-contribution-69-364@zakopane.if.uj.edu.pl
DESCRIPTION:Speakers: Shlomi Reuveni (Tel Aviv University)\nStopping a pro
cess in its midst—only to start it all over again—may prolong\, leave
unchanged\, or even shorten the time taken for its completion. Among these
three possibilities\, the latter is particularly interesting as it sugges
ts that restart can be used to expedite the completion of complex processe
s involving strong elements of chance. This turned out to be important in
computer science where restart drastically improves performance of randomi
zed algorithms\, but is not less relevant to many physical\, chemical\, an
d biological processes where restart plays a central role. In this talk\,
I will provide an introduction to the theory of restart phenomena and revi
ew some of its applications in statistical\, chemical\, and biological phy
sics. \n\nReferences\n\n[1] S. Reuveni\, Phys. Rev. Lett. **116**\, 170601
(2016).\n[2] A. Pal & S. Reuveni\, Phys. Rev. Lett. **118**\, 030603 (201
7).\n[3] A. Pal\, I. Eliazar & S. Reuveni\, Phys. Rev. Lett. **122**\, 020
602 (2019).\n[4] S. Ray\, D. Mondal & S. Reuveni\, J. Phys. A. **52**\, 25
5002 (2019).\n[5] S. Ray & S. Reuveni\, J. Chem. Phys. **152**\, 234110 (2
020).\n[6] O. T. Friedman\, A. Pal\, A. Sekhon\, S. Reuveni & Y. Roichman\
, J. Phys. Chem. Lett. **11**\, 7350 (2020).\n[7] A. Pal\, Ł. Kuśmierz &
S. Reuveni\, Phys. Rev. Research **2**\, 043174 (2020).\n\nhttps://zakopa
ne.if.uj.edu.pl/event/16/contributions/364/
LOCATION:
URL:https://zakopane.if.uj.edu.pl/event/16/contributions/364/
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