Instantaneous Gelation in Smoluchwski's Coagulation Equation Revisited, Confe...Colm Connaughton
Invited talk given at "Boltzmann equation:
mathematics, modeling and simulations
In memory of Carlo Cercignani", Institut Henri Poincare, Paris, February 11, 2011.
Talk given at the workshop "Multiphase turbulent flows in the atmosphere and ocean", National Centre for Atmospheric REsearch, Boulder CO, August 15 2012
Instantaneous Gelation in Smoluchwski's Coagulation Equation Revisited, Confe...Colm Connaughton
Invited talk given at "Boltzmann equation:
mathematics, modeling and simulations
In memory of Carlo Cercignani", Institut Henri Poincare, Paris, February 11, 2011.
Talk given at the workshop "Multiphase turbulent flows in the atmosphere and ocean", National Centre for Atmospheric REsearch, Boulder CO, August 15 2012
Chemical dynamics and rare events in soft matter physicsBoris Fackovec
Talk for the Trinity Math Society Symposium. First summarises the approximations leading from Dirac equation to molecular description and then the synthesis towards non-equilibrium statistical mechanics. The relaxation approach to projection of a molecular system to a Markov jump process is discussed.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Normal Labour/ Stages of Labour/ Mechanism of LabourWasim Ak
Normal labor is also termed spontaneous labor, defined as the natural physiological process through which the fetus, placenta, and membranes are expelled from the uterus through the birth canal at term (37 to 42 weeks
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Nonequilibrium Statistical Mechanics of Cluster-cluster Aggregation Warwick Mathematics Colloquium May 2011
1. Nonequilibrium statistical mechanics of
cluster-cluster aggregation
Colm Connaughton
Mathematics Institute and Centre for Complexity Science,
University of Warwick, UK
Collaborators: R. Ball (Warwick), P. Krapivsky (Boston), R. Rajesh (Chennai), T.
Stein (Reading), O. Zaboronski (Warwick).
Mathematics Colloquium
University of Warwick
20 May 2011
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
2. Aggregation phenomena : motivation
Many particles of one
material dispersed in
another.
Transport is diffusive or
advective.
Particles stick together on
contact.
Applications: surface physics, colloids, atmospheric science,
earth sciences, polymers, cloud physics.
This talk:
Today we will focus on simple theoretical models of the
statistical dynamics of such systems.
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
3. Simplest model of clustering: coalescing random
walks
Particles perform random walks on a
lattice.
Multiple occupancy of lattice sites is
allowed.
Particles on the same site merge
with probability rate k : A + A → A.
A source of particles may or may not
be present.
Cartoon of dynamics in No equilibrium - lack of detailed
1-D with k → ∞. balance.
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
4. Mean field description
Equation for the average density, N(x, t), of particles:
∂t N = D ∆ N − 1 k N (2) + J
2
k - reaction rate, D - diffusion rate, J - injection rate, N (2) -
density of same-site pairs.
Mean field assumption:
No correlations between particles: N (2) ∝ N 2 :
Spatially homogeneous case, N(x, t) = N(t).
Mean field rate equation:
dN
= − 2 k N2 + J
1
N(0) = N0
dt
2 N0 1
J = 0 : N(t) = ∼ as t → ∞
2 + k N0 t kt
2J
J = 0 : N(t) ∼ as t → ∞
k
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
5. A more sophisticated model of clustering:
size-dependent coalescence
A better model would track the sizes distribution of the clusters:
Am1 + Am2 → Am1 +m2 .
Probability rate of particles sticking should be a function,
K (m1 , m2 ), of the particle sizes (bigger particles typically
have a bigger collision cross-section).
Micro-physics of different applications is encoded in
K (m1 , m2 ) - the collision kernel - which is often a
homogeneous function:
K (am1 , am2 ) = aλ K (m1 , m2 )
Given the kernel, objective is to determine the cluster size
distribution, Nm (t), which describes the average number of
clusters of size m as a function of time.
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
6. The Smoluchowski equation
Assume the cloud is statistically homogeneous and well-mixed
so that there are no spatial correlations.
Cluster size distribution, Nm (t), satisfies the kinetic equation :
Smoluchowski equation :
∞
∂Nm (t)
= dm1 dm2 K (m1 , m2 )Nm1 Nm2 δ(m − m1 − m2 )
∂t 0
∞
− 2 dm1 dm2 K (m, m1 )Nm Nm1 δ(m2 − m − m1 )
0
+ J δ(m − m0 )
Notation: In many applications kernel is homogeneous:
K (am1 , am2 ) = aλ K (m1 , m2 )
µ ν
K (m1 , m2 ) ∼ m1 m2 m1 m2 .
Clearly λ = µ + ν.
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
7. Self-similar Solutions of the Smoluchowski equation
In many applications kernel
is a homogeneous function:
K (am1 , am2 ) = aλ K (m1 , m2 )
Resulting cluster size
distributions often exhibit
self-similarity.
Self-similar solutions have the form
m
Nm (t) ∼ s(t)−2 F (z) z=
s(t)
where s(t) is the typical cluster size. The scaling function, F (z),
determines the shape of the cluster size distribution.
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
8. Stationary solutions of the Smoluchowski equation
with a source of monomers
Add monomers at rate, J.
Suppose particles having
m > M are removed.
Stationary state is obtained
for large t.
Stationary state is a
balance between injection
and removal. Constant
mass flux in range [m0 , M]
With some work exact stationary solution can be found:
√ λ+3
Nm (t) ∼ CK J m− 2 as t → ∞.
Require mass flux to be local: |µ − ν| < 1.
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
9. Violation of mass conservation: the gelation transition
Microscopic dynamics conserve mass: Am1 + Am2 → Am1 +m2 .
Smoluchowski equation formally
conserves the total mass,
∞
M1 (t) = 0 m N(m, t) dm.
However for λ > 1:
∞
M1 (t) < m N(m, 0) dm t > t ∗ .
0
(Lushnikov [1977], Ziff [1980])
M1 (t) for K (m1 , m2 ) = (m1 m2 ) 3/4
. Mean field theory violates mass
conservation!!!
Best studied by introducing cut-off, M, and studying limit
M → ∞. (Laurencot [2004])
What is the physical interpretation?
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
10. Physical interpretation of the gelation transition
As λ increases, the aggregation rate, K (m1 , m2 ), increases
more rapidly as a function of m. If λ > 1 the absorbtion of
small clusters by large ones becomes a runaway process.
Clusters of arbitrarily large size (gel) are generated in a
finite time, t∗ , known as the gelation time.
Loss of mass to the gel component corresponds to a finite
mass flux as m → ∞.
Finite time singularities generally pose a problem for
physics: for gelling systems Smoluchowski equation
usually only describes intermediate asymptotics of Nm (t).
In qualitative agreement with experiments in crosslinked
polymer aggregation (Lushnikov et al. [1990]).
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
11. Instantaneous gelation
Asymptotic behaviour of the kernel controls the aggregation of
small clusters and large:
µ ν
K (m1 , m2 ) ∼ m1 m2 m1 m2 .
µ + ν = λ so that gelation always occurs if ν is big enough.
Instantaneous Gelation
If ν > 1 then t ∗ = 0. (Van Dongen & Ernst [1987])
Worse: gelation is complete: M1 (t) = 0 for t > 0.
Instantaneously gelling kernels cannot describe even the
intermediate asymptotics of any physical problem.
Mathematically pathological?
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
12. Droplet coagulation by gravitational settling: a puzzle
The process of gravitational
settling is important in the
evolution of the droplet size
distribution in clouds and
the onset of precipitation.
Droplets are in the Stokes
regime → larger droplets
fall faster merging with
slower droplets below them.
Some elementary calculations give the collision kernel
1 1 2 2
K (m1 , m2 ) ∝ (m1 + m2 )2 m1 − m2
3 3 3 3
ν = 4/3 suggesting instantaneous gelation but model seems
reasonable in practice. How is this possible?
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
13. Instantaneous gelation in the presence of a cut-off
With cut-off, M, regularized
∗
gelation time, tM , is clearly
identifiable.
∗
tM decreases as M increases.
Van Dongen & Ernst recovered in
limit M → ∞.
3
2 3/2
M(t) for K (m1 , m2 ) = m1 + m2 .
Decrease of ∗
tM as M is very slow. Numerics and heuristics
suggest:
∗ 1
tM ∼ .
log M
This suggests such models are physically reasonable.
Consistent with related results of Krapivsky and Ben-Naim
and Krapivsky [2003] on exchange-driven growth.
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
14. "Instantaneous" gelation with a source of monomers
A stationary state is reached in the regularised systems if a
source of monomers is present (Horvai et al [2007]).
Stationary state has the
asymptotic form for M 1:
J log M ν−1 m1−ν −ν
Nm = M m .
M
Stretched exponential for small
m, power law for large m.
Stationary state (theory vs numerics)
Stationary particle density:
for ν = 3/2.
√ 1−ν
J M − MM J
N= ∼ as M → ∞.
M log M ν−1 log M ν−1
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
15. Approach to Stationary State is non-trivial
Numerics indicate that the
approach to stationary state is
non-trivial.
Collective oscillations of the total
density of clusters.
Total density vs
1+
time for
1+
Numerical measurements of the
K (m1 , m2 ) = m1 + m2 .
Q-factor of these oscillations
suggests that they are long-lived
transients. Last longer as M
increases.
Heuristic explanation in terms of
“reset” mechanism.
“Q-factor" for ν = 0.2.
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
16. The addition model: a completely nonlocal limit
The extreme case of nonlocal aggregation is the Addition
model (Brilliantov & Krapivsky, 1992).
Clusters can only grow by absorption of monomers:
M
˙ 2
N1 = −2 γ N1 − κ(m)N1 Nm + J,
m=2
˙
Nm = κ(m − 1)N1 Nm−1 − κ(m)N1 Nm 2 ≤ m ≤ M,
with κ(m) ∼ mν . Instantaneously gelling for ν > 1.
Stationary state:
√ J
Nm = γ m−ν .
M +1
Large mass behaviour agrees with Smoluchowski model if
we choose effective monomer reaction rate γ = M −1 .
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
17. Oscillatory approach to stationary state in the addition
model
Addition model with effective monomer reaction rate captures
the essential features of the full problem when ν > 1.
It can be (almost) linearised by a change of variables:
dτ (t) = N1 (t)dt,
τ (0) = 0.
Look for solution of the resulting monomer equation of the form:
J
N1 (τ ) = (1 + Aeζτ ),
γ (M + 1)
where Re ζ < 0. Asymptotics are tractable for ν = 1 + .
Find: |Re ζ| = O( ), Im ζ = O(1). This implies long-lived
oscillatory transient.
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
18. Summary and conclusions
Aggregation phenomena exhibit a rich variety of
non-equilibrium statistical dynamics.
If the aggregation rate of large clusters increases quickly
enough as a function of cluster size, clusters of arbitrarily
large size can be generated in finite time (gelation).
Kernels with ν > 1 which, mathematically speaking,
undergo complete instantaneous gelation still make sense
as physical models provided a cut-off is included since the
approach to the singularity is logarithmically slow as the
cut-off is removed.
Approach to stationary state for regularised system with a
source of monomers is interesting when ν > 1: surprisingly
long-lived oscillatory transients.
Some analytical insight can be obtained from the addition
model with renormalised monomer reaction rate.
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech
19. References
R.C. Ball, C. Connaughton, T.H.M. Stein and O. Zaboronski, "Instantaneous Gelation in Smoluchowski’s
Coagulation Equation Revisited", preprint arXiv:1012.4431v1 [cond-mat.stat-mech], 2010
C. Connaughton, R. Rajesh, and O. Zaboronski "On the Non-equilibrium Phase Transition in
Evaporation-Deposition Models", J. Stat. Mech.-Theor. E., P09016, 2010
C. Connaughton and J. Harris, "Scaling properties of one-dimensional cluster-cluster aggregation with Levy
diffusion", J. Stat. Mech.-Theor. E., P05003, 2010
C. Connaughton and P.L. Krapivsky "Aggregation-fragmentation processes and decaying three-wave
turbulence ", Phys. Rev. E 81, 035303(R), 2010
C. Connaughton, R. Rajesh and O. Zaboronski, "Constant Flux Relation for diffusion limited cluster–cluster
aggregation", Phys. Rev E 78, 041403, 2008
C. Connaughton,R. Rajesh and O. Zaboronski , "Constant Flux Relation for Driven Dissipative Systems",
Phys. Rev. Lett. 98, 080601 (2007)
C. Connaughton,R. Rajesh and O. Zaboronski , "Cluster-Cluster Aggregation as an Analogue of a Turbulent
Cascade : Kolmogorov Phenomenology, Scaling Laws and the Breakdown of self-similarity", Physica D 222,
1-2 97-115 (2006)
C. Connaughton R. Rajesh and O.V. Zaboronski, "Breakdown of Kolmogorov Scaling in Models of Cluster
Aggregation", Phys. Rev. Lett. 94, 194503 (2005)
C. Connaughton R. Rajesh and O.V. Zaboronski, "Stationary Kolmogorov solutions of the Smoluchowski
aggregation equation with a source term", Phys. Rev E 69 (6): 061114, 2004
http://www.slideshare.net/connaughtonc arXiv:1012.4431 cond-mat.stat-mech