CROSSING A PHASE TRANSITION OUT OF EQUILIBRIUMleticia/THESIS/alberto-si... · 2009. 10. 6. ·...
Transcript of CROSSING A PHASE TRANSITION OUT OF EQUILIBRIUMleticia/THESIS/alberto-si... · 2009. 10. 6. ·...
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CROSSING A PHASE TRANSITION OUT OF EQUILIBRIUM
Alberto Sicilia Garcia
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Crossing a phase transition out of equilibrium
Phases of matter
Matter can be found in many different phases.
• Characterize the phases of matter is a central problem in many fields of physics.
Energy scale.
: .Cosmology Phases of matter in the first instants of the universe
: - .QCD gluon plasma phase transition
: .Biophysics phases of polymers in a solution
: / / .Condensed matter insulator conductor superconductor
:Some examples
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Out of equilibrium dynamics
( . ).Changing abruptly a control parameter ex the temperature
( . ).Changing abruptly a microscopical parameter ex a coupling constant
How?
Crossing a phase transition out of equilibrium
• Great advances have been made in the study of equilibrium properties of phase transitions.
• A natural step forward: what happens if we force the system to cross out of equilibrium a phase transition?
• The system will evolve on time until reaching its new equilibrium state. Slow dynamics (“aging”).
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Out of equilibrium dynamics
( . ).Changing abruptly a control parameter ex the temperature
( . ).Changing abruptly a microscopical parameter ex a coupling constant
How?
Crossing a phase transition out of equilibrium
• Great advances have been made in the study of equilibrium properties of phase transitions.
• A natural step forward: what happens if we force the system to cross out of equilibrium a phase transition?
• Note that this is only a particular example of an out of equilibrium process. One can also study, for example, out of equilibrium stationary states:
.Coupling the system at two thermal resevoirs at different temperatures
(“ ”).Constantly injecting energy to the system shaking
• The system will evolve on time until reaching its new equilibrium state. Slow dynamics (“aging”).
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Out of equilibrium dynamics
• Great advances have been made in the study of equilibrium properties of phase transitions.
• A natural step forward: what happens if we force the system to cross out of equilibrium a phase transition?
( . ).Changing abruptly a control parameter ex the temperature
( . ).Changing abruptly a microscopical parameter ex a coupling constant
How?
• The system will evolve on time until reaching its new equilibrium state. Slow dynamics (“aging”).
• Note that this is only a particular example of an out of equilibrium process. One can also study, for example, out of equilibrium stationary states:
.Coupling the system at two thermal resevoirs at different temperatures
(“ ”).Constantly injecting energy to the system shaking
Crossing a phase transition out of equilibrium
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Defect formation
• When crossing a phase transition out of equilibrium, defects are created.
• On the subsequent time evolution, defects will progressively disappear until the system reaches the new equilibrium state.
• A possible way to study the out of equilibrium evolution of the system is then to focus on defect dynamics.
What defects are?
Why are they created when crossing a phase transition?
But...
Crossing a phase transition out of equilibrium
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T>TcTc
FERRO PARAMAGNETIC
T<Tc
F [] F []
x x
Crossing a phase transition out of equilibrium
Defect formation
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Revising the classical KZ mechanism: a new proposal
T(t)
T>TcTcT<Tc
Defect formation
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F []
T(t)
x
T>TcTcT<Tc
Crossing a phase transition out of equilibrium
Defect formation
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F [] F []
x
T(t)
x
T>TcTcT<Tc
Defect formation
Crossing a phase transition out of equilibrium
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Revising the classical KZ mechanism: a new proposal
F [] F []
x
T(t)
x
T>TcTcT<Tc
Defect formation
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Crossing a phase transition out of equilibrium
Defect formation
Below Tc, the order parameter must choose a vacuum.
But in different regions of the space, the order parameter chooses different vacua...
⇒ Formation of TOPOLOGICAL defects.
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Domain Walls: Closed hypersurfaces in d-1 dimensions.
An Example of topological defects.
Below Tc, the order parameter must choose a vacuum.
⇒ Formation of TOPOLOGICAL defects.
But in different regions of the space, the order parameter chooses different vacua...
Crossing a phase transition out of equilibrium
Defect formation
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Domain Walls: Closed hypersurfaces in d-1 dimensions.
An Example of topological defects.
Below Tc, the order parameter must choose a vacuum.
⇒ Formation of TOPOLOGICAL defects.
But in different regions of the space, the order parameter chooses different vacua...
Crossing a phase transition out of equilibrium
Defect formation
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Depending on...
- Domain walls.
- Strings.
- Monopoles.
- Textures.
- The nature of the order parameter (space and field dimensionalities, scalar/vector, real/complex...).
- How the symmetry is broken.
⇒ Different kinds of topological defects!
Crossing a phase transition out of equilibrium
Defect formation
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GOAL OF THIS THESIS:
“Gain some understanding in the dynamics of systems forced to cross a phase transition out of equilibrium.”
In particular, study this problem from a geometrical point of view: focusing on defect dynamics.
Goal of the thesis
Crossing a phase transition out of equilibrium
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Particular problems we studied
An equilibrium prelude: .Geometrical properties of critical parafermionic models
with R. Santachiara and M. Picco.
Out-of-equilibrium dynamics: .Geometry of domain growth in 2d
with J. Arenzon, A. Bray, LFC, I. Dierking and Y. Sarrazin.
: Relaxation in spatially extended chaotic systems coupled map.lattices
with E. Katzav and LFC.
.Coarsening in the Potts model
with J. Arenzon, A. Bray, LFC and M. Loureiro.
- .Revision of the classical Kibble Zurek mechanism
with G. Biroli and LFC.
- - - . Equilibrium and out of equilibrium dynamics of the Blume Capel model
with C. Aron, M. Baitsy-Jessi and LFC.
Crossing a phase transition out of equilibrium
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Particular problems we studied
An equilibrium prelude: .Geometrical properties of critical parafermionic models
with R. Santachiara and M. Picco.
Out-of-equilibrium dynamics: .Geometry of domain growth in 2d
with J. Arenzon, A. Bray, LFC, I. Dierking and Y. Sarrazin.
: Relaxation in spatially extended chaotic systems coupled map.lattices
with E. Katzav and LFC.
.Coarsening in the Potts model
with J. Arenzon, A. Bray, LFC and M. Loureiro.
- .Revision of the classical Kibble Zurek mechanism
with G. Biroli and LFC.
- - - . Equilibrium and out of equilibrium dynamics of the Blume Capel model
Crossing a phase transition out of equilibrium
with C. Aron, M. Baitsy-Jessi and LFC.
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SUMMARY OF THE TALK
1.- Phenomenology of “domain growth” (“coarsening”, “phase ordering dynamics”).
2.- OUR WORK: Geometrical description of 2d domain growth.
3.- Conclusions.
Crossing a phase transition out of equilibrium
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1.- PHENOMENOLOGY OF DOMAIN GROWTH
Crossing a phase transition out of equilibrium
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What is domain growth?
T
M
Tc
FERROPARAMAGNETIC
Crossing a phase transition out of equilibrium
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Domain growth morphology in two dimensions
What is domain growth?
T
M
Tc Tix
SYSTEM IN EQUILIBRIUM
Crossing a phase transition out of equilibrium
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What is domain growth?
T
M
Tc TixTfxFAST QUENCH
Crossing a phase transition out of equilibrium
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Domain growth morphology in two dimensions
What is domain growth?
T
M
Tc
Tfx
Meq(Tf) -- x
The system will relax to the new equilibrium state... but HOW???
Crossing a phase transition out of equilibrium
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What is domain growth?
T
M
Tc
Tfx
Meq(Tf) -- x
TfTf
Meq(Tf) --
t=0 time t=teq.
The system will relax to the new equilibrium state... but HOW???
Equilibrium Ti Equilibrium Tf
Crossing a phase transition out of equilibrium
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What is domain growth?
T
M
Tc
Tfx
Meq(Tf) -- x
TfTf
Meq(Tf) --
t=0 time t=teq.
This process is known as DOMAIN GROWTH (also refered as 'phase ordering' or 'coarsening').
The system will relax to the new equilibrium state... but HOW???
➢ Present in many different systems.
Equilibrium Ti Equilibrium Tf
Crossing a phase transition out of equilibrium
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What is domain growth?
If we measure all distances in units of R(t), the system is statiscally the same at any time.
➢ There exists a characteristic length scale R(t):
DYNAMICAL SCALING HYPOTHESIS
Crossing a phase transition out of equilibrium
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What is domain growth?
If we measure all distances in units of R(t), the system is statiscally the same at any time.
➢ There exists a characteristic length scale R(t):
➢ Suggested by experiments and numerical simulations.
DYNAMICAL SCALING HYPOTHESIS
Crossing a phase transition out of equilibrium
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What is domain growth?
If we measure all distances in units of R(t), the system is statiscally the same at any time.
➢ There exists a characteristic length scale R(t):
➢ Suggested by experiments and numerical simulations.
DYNAMICAL SCALING HYPOTHESIS
➢ Proven in:- 1d Ising Model with Glauber dynamics.
- Langevin dynamics of O(N) model when N → ∞
(A. J. Bray, 1994).
Crossing a phase transition out of equilibrium
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What is domain growth?
If we measure all distances in units of R(t), the system is statiscally the same at any time.
➢ There exists a characteristic length scale R(t):
➢ Suggested by experiments and numerical simulations.
➢ There was no analitycal proof in 2d.
DYNAMICAL SCALING HYPOTHESIS
➢ Proven in:- 1d Ising Model with Glauber dynamics.
- Langevin dynamics of O(N) model when N → ∞
(A. J. Bray, 1994).
Crossing a phase transition out of equilibrium
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3.- OUR WORK:GEOMETRICAL DESCRIPTION OF 2D
DOMAIN GROWTH
Crossing a phase transition out of equilibrium
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Mathematical formalism
➢ Mathematical model we used: Langevin equation.
➢ .There are other mathematical models one could consider
- - , .Instead of a coarse grained field a more microscopical approach
- , .Instead of a continuous order parameter a lattice model
- , .Instead of a Langevin equation a master equation
- , .Instead of a classical system a quantum system
:Examples
- , ( .).Instead of stochastic dynamics deterministic dynamics Hamilton eqs
Crossing a phase transition out of equilibrium
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Distribution of areas in quenches to T=0
Crossing a phase transition out of equilibrium
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Geometrical Description of 2D Domain Growth
▪ Our defects are the domain walls (a.k.a. “hulls”).
▪ .Two different areas associated to each domain wall
A1A2
A3A4
➢ Domain area.
There are 4 domains with:areas
➢ Hull enclosed area. There are 4 hulls with enclosed:areas
A1
A2
A3
A4
A1+A
2A1
A4
A1+A
2+A
3+A
4
( Area distributions densities and ).per unit area of the systemnd(A,t) nh(A,t)
Crossing a phase transition out of equilibrium
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Coarsening does not proceed by coalescence of small domains.
Distribution of areas in a quench to T=0
Crossing a phase transition out of equilibrium
➢ From Langevin equation at T=0, Allen and Cahn (1979),
➢ The velocity of a wall in each point is proportional to its local curvature.
➢ Velocity points in the direction of reducing curvature.
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➢ From Langevin equation at T=0, Allen and Cahn (1979),
➢ The velocity of a wall in each point is proportional to its local curvature.
➢ Velocity points in the direction of reducing curvature.
Coarsening does not proceed by coalescence of small domains.
➢ Integrating the Allen-Cahn eq. around a hull:
???
Distribution of areas in a quench to T=0
Crossing a phase transition out of equilibrium
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???
➢ We can use the Gauss-Bonnet th.
➢ Hull-enclosed areas are flat 2d manifolds with no holes.
➢ Evolution equation for hull-enclosed areas:
➢ Hull enclosed areas evolve independently one from another.
➢ They all shrink at a constant rate, independently of their size.
Distribution of areas in a quench to T=0
Crossing a phase transition out of equilibrium
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➢ If you know the distribution at initial time, when the system is quenched, you know the distribution at any time during the evolution.
➢ Remember, we are quenching our system to T=0.
➢ Before the quench, the system is in equilibrium at some temperature T>Tc.
➢ The two extreme cases are:
T>TcTcT=0
Quench from the critical temperature.
Quench from infinite temperature.
Distribution of areas in a quench to T=0
Crossing a phase transition out of equilibrium
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➢ We are lucky, because the equilibrium distributions for both initial cases are known (Cardy and Ziff, 2002):
T0= Tc
Critical percolation ⇔ T0= ∞
➢ Pluging-in these initial distributions into the evolution equation:
Quench to T=0 from T0= ∞
Quench to T=0 from T0= Tc
➢ The distributions have the scaling form,
Scaling dynamical hypothesis is recovered from calculation!
Distribution of areas in a quench to T=0
Crossing a phase transition out of equilibrium
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Domain growth morphology in two dimensions
Numerical verification of our exact result
Crossing a phase transition out of equilibrium
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Numerical verification of our exact result
Crossing a phase transition out of equilibrium
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Numerical verification of our exact result
Crossing a phase transition out of equilibrium
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Geometrical Description of 2D Domain Growth
What happens for the domain areas?
➢ The evolution of a domain area will depend, in general on the movement of several walls.
Crossing a phase transition out of equilibrium
A1A2
A3A4
For example, the evolution of A3 :
In general :
Domain can grow/shrink/remain constant.
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Distribution of areas in a quench to T=0
Crossing a phase transition out of equilibrium
➢ Initial distributions are also known for domain areas.
➢ Taking advantage of the smallness of ch one can (approximately) show:
➢ Two important sum rules:
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Crossing a phase transition out of equilibrium
Distribution of areas in a quench to T=0
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Effects of finite working temperature
Crossing a phase transition out of equilibrium
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T = 0 T = 1.5time = 32 MCS
Domain area distributions during coarsening at T≠0
Crossing a phase transition out of equilibrium
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T = 0 T = 1.5time = 32 MCS
➢ Roughens the domain walls.➢ Generates 'thermal domains' (not formed by coarsening).
EFFECTS OF TEMPERATURE:
Domain area distributions during coarsening at T≠0
Crossing a phase transition out of equilibrium
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where➢ Distribution of domains areas during coarsening at T=0.
Domain area distributions during coarsening at T≠0
Crossing a phase transition out of equilibrium
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➢ Temperature dependence enters through prefactor (T)
where➢ Distribution of domains areas during coarsening at T=0.
Domain area distributions during coarsening at T≠0
➢ Dynamical RG: dynamics at T<Tc controlled by T=0 fixed point.
Crossing a phase transition out of equilibrium
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➢ Temperature dependence enters through prefactor (T)
where
➢ How to measure (T)?
From the spatial-correlation function
which scales with
➢ Distribution of domains areas during coarsening at T=0.
Domain area distributions during coarsening at T≠0
➢ Dynamical RG: dynamics at T<Tc controlled by T=0 fixed point.
Crossing a phase transition out of equilibrium
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Domain area distributions during coarsening at T≠0
➢ Let us test our prediction:
➢ Simulations in the 2d Ising Model.
where
Crossing a phase transition out of equilibrium
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Domain area distributions during coarsening at T≠0
➢ Let us test our prediction:
➢ Simulations in the 2d Ising Model.
where
Crossing a phase transition out of equilibrium
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Domain area distributions during coarsening at T≠0
➢ Let us test our prediction:
➢ Simulations in the 2d Ising Model.
where
Crossing a phase transition out of equilibrium
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Domain area distributions during coarsening at T≠0
➢ Let us test our prediction:
Zoom on the small domain region:
➢ Simulations in the 2d Ising Model.
where
Crossing a phase transition out of equilibrium
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Domain area distributions during coarsening at T≠0
➢ Let us test our prediction:
Zoom on the small domain region:
➢ Simulations in the 2d Ising Model.
where
Crossing a phase transition out of equilibrium
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Fractal structure of the domains
Crossing a phase transition out of equilibrium
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Domain growth morphology: area vs. perimeter.
t=0
Crossing a phase transition out of equilibrium
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Domain growth morphology: area vs. perimeter.
t=0
Crossing a phase transition out of equilibrium
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Domain growth morphology: area vs. perimeter.
t=0
Crossing a phase transition out of equilibrium
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Domain growth morphology: area vs. perimeter.
t=0
Crossing a phase transition out of equilibrium
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Domain growth morphology: area vs. perimeter.
t=0
Crossing a phase transition out of equilibrium
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UNROUGHENING TRANSITION!
Domain growth morphology: area vs. perimeter.
t=0
➢ Regular➢ Fractal as the initial state
Crossing a phase transition out of equilibrium
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Distributions of domain perimeters
We know➢ Distributions of areas
➢ Relation area - perimeterDistributions of perimeters
Crossing a phase transition out of equilibrium
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Distributions of domain perimeters
We know➢ Distributions of areas
➢ Relation area - perimeterDistributions of perimeters
Crossing a phase transition out of equilibrium
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Distributions of domain perimeters
We know➢ Distributions of areas
➢ Relation area - perimeterDistributions of perimeters
Crossing a phase transition out of equilibrium
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Distributions of domain perimeters
We know➢ Distributions of areas
➢ Relation area - perimeterDistributions of perimeters
Crossing a phase transition out of equilibrium
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Distributions of domain perimeters
We know➢ Distributions of areas
➢ Relation area - perimeterDistributions of perimeters
if
if
Crossing a phase transition out of equilibrium
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Distributions of domain perimeters
We know➢ Distributions of areas
➢ Relation area - perimeterDistributions of perimeters
if
if
Crossing a phase transition out of equilibrium
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Experiments in liquid crystals
Crossing a phase transition out of equilibrium
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Experimental application of our result
➢ Quasi 2-d cell filled with the liquid crystal
➢ “bent core” liquid crystals.
➢ Application of an electric field ⇒ Growth of chiral domains
Right handed domains Left handed domains
Crossing a phase transition out of equilibrium
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Experimental application of our result
Crossing a phase transition out of equilibrium
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Experimental application of our result
Domain growth morphology in two dimensionsDomain growth morphology in two dimensionsDomain growth morphology in two dimensionsCrossing a phase transition out of equilibrium
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CONCLUSIONS
Crossing a phase transition out of equilibrium
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Conclusions and Future Work
➢ Proof of Dynamical Scaling Hypothesis in 2D.
➢ Analytic, Numerical and Experimental results.
➢ Geometrical Picture of 2D Coarsening.
➢ Refs. for the results presented today: PRL 98, 145701 (2007), PRE 76, 061116 (2007), EPL 82, 10001 (2008), PRL 101, 197801 (2008).
➢ Role played by different initial conditions.
➢ Role played by the working temperature.
Crossing a phase transition out of equilibrium
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Effects of weak quenched disorder
Crossing a phase transition out of equilibrium
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Effects of the disorder
Crossing a phase transition out of equilibrium
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Effects of the disorder
Crossing a phase transition out of equilibrium
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Effects of the disorder
DISTRIBUTION OF DOMAIN SIZES
Crossing a phase transition out of equilibrium
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Effects of the disorder
DISTRIBUTION OF DOMAIN PERIMETERS
Crossing a phase transition out of equilibrium