Name : Supurna SinhaAcademic Career : Ph.D. (Physics) Syracuse University 1992
: Title of Thesis
Collective Dynamics in
Dense Fluid Mixtures
: Ph.D. Advisor
M. Cristina Marchetti
Positions Held in the past :
1. JNC Fellow,
Jawaharlal Nehru Centre for Advanced Scientific Research
and Department of Physics,
Indian Institute of Science, Bangalore, India.
2. Visiting Scientist,
Centre for Theoretical Studies,
Indian Institute of Science, Bangalore, India.
3. Post Doctoral Fellow,
4. Visiting Faculty,
Harish Chandra Research Institute (HRI),
School Certificate(1979) Visvabharati University 81% (First Division) (1st Rank)
77% (star marks:First Division)
(Letter Marks in Physics).
Physics (Hons.) 80%
(First Class: 2ndRank)
Physics: CGPA 3.92 on a scale of 4.0
Title: ``Collective Dynamics in
Dense Fluid Mixtures''
Synopsis of PhD. Thesis:
My thesis deals with the short wavelength collective
dynamics of dense binary fluid mixtures. The analysis shows that at the
level of linearised generalised hydrodynamics, the longitudinal modes
of the system separate essentially into two parts- one, involves the
coupling of partial density fluctuations of the two species and the
other involves the coupling of longitudinal momentum and temperature
fluctuations. We have shown that the coupling of longitudinal momentum
and temperature fluctuations leads to an adequate description of sound
propagation in such systems. In particular, we show that structural
disorder controls the trapping of sound waves in dense mixtures. The
coupling of the partial density fluctuations of the two species leads
to a simple description of the partial dynamic structure factors. We
find that our results are in agreement with the molecular dynamics
simulations of soft sphere mixtures. The partial density fluctuations
are the slowest decaying fluctuations on molecular length scales and it
turns out that nonlinear coupling of these slow modes lead to important
corrections to the long time behavior of the time correlation functions
determining the shear viscosity in dense mixtures.
Highlights of Research Publications and their impact:
During my postdoctoral stay at the Indian Institute
of Science I had written a single author paper on Dynamic Structure
of a Dense Binary Mixture in which I had made certain predictions about the diffusional dynamics of glassy mixtures which have
been corroborated by a Harvard Group of experimentalists (See for instance, A. D. Dinsmore, E. R. Weeks, V. Prasad, A. Levitt and D. A. Weitz, Applied Optics, Vol. 40, 4152, 2001). Subsequently, during my postdoctoral tenure at RRI I had written a single author paper
on Low Temperature Decoherence which has influenced experimental work in this area by a Caltech group of
experimenters (See, for instance, Webb et al, Fortschrift Phys. Vol. 46, 779, 1998). The power law loss of coherence
predicted in my paper has been seen in NMR spectra of proteins and vibrational spectra
of highly excited molecules at Urbana (See, for instance, V. Wong et al , Physical Review A, Vol. 63, 022502, 2001).
My work on dense binary mixtures with M. C.
Marchetti has been appreciated by the glass transition research
community (for instance, P. T. Visscher, in a letter to M. C. Marchetti
and E. G. D. Cohen, at a stat-mech meeting, have personally acknowledged the importance of our work ). It has also influenced the course of glass transition theory in mixtures ( See for instance, U. Harbola and S. P. Das, Physical Review E 65, 036138 (2002)).
One of my papers with M. C. Marchetti in this area has been included in a special collection of papers on `Thermal and Statistical Physics'.
My paper on Brownian Motion at Absolute Zero written
with R. D. Sorkin
predicts, on the basis of the fluctuation-dissipation
theorem, a logarithmic growth of mean square displacement with
time . W. D. Phillips ( NIST, 1997 Nobel Prize) had found such a
model independent prediction
for the slow growth of mean square displacement at low temperatures intriguing and had discussed it in some detail with R . D. Sorkin and me and had shown interest in checking the claim experimentally.
My work on Laser Induced Freezing of Colloids
written with J. Chakrabarti led to certain predictions
regarding the effect of fluctuations on the re-entrant phase. These predictions have been corroborated in
state-of-the art experiments ( See, for instance, Wei et al, PRL, Vol 81, 2606, 1998).
My work with J. Samuel on Brownian
Motion and Magnetism where we had mentioned the connection
with polymer distribution functions, has found a very timely and relevant application in the area of semiflexible polymers in
biological physics. Our work in this area of biological physics has been appreciated by active researchers in this area such as
S. Stepanow and Y. Rabin (See, for instance, S. Stepanow and
G. M. Schutz , Europhys. Lett. 60, 546 (2002)).
One of our papers in this area has been described by the referee
as `` a timely contribution to the rapidly growing field of biological physics '' and ``an important contribution to the field''.
My single author paper ``Writhe distribution of
stretched polymers'' published in Physical Review E has been noticed by the American Journal Experts
who have been impressed by the quality of the research
and the thought behind my paper. It has also been much appreciated
by a referee of the paper who commented:
``I do like the paper and its simple results. It is also an exceptionally
honest paper, since it states the limits of this presented analytical
theory in a remarkable way!''
The editor of Journal of Physics Condensed Matter
has brought it to our attention that
our recent paper ``DNA elasticity :topology of self avoidance'' which
has appeared in JPCM (2006) in the
special issue on biopolymers has been downloaded 128 times
as recorded till Sep, 2006. [See, http://www.iop.org/journals/jpcm]
Our paper ``Euler buckling in red blood cells ...''
written in collaboration with a TIFR , Mumbai group of experimenters has
been highlighted by New Scientist [See the coverage of this work
in the August 20, 2005 issue].
Recently, we have developed an intriguing analogy
surface tension of membranes in condensed matter and the notion
of cosmological constant in the context of gravity. Our analogy
realizes a compelling idea due to R. D. Sorkin which traces the small
finite observed magnitude of the cosmological constant to the
underlying discreteness of spacetime structure on quantum
gravity scales. We propose a soft condensed matter experiment
to realize this analog quantum gravity prediction.
[See ``Surface tension and the cosmological constant'', J. Samuel
and Supurna Sinha, Physical Review Letters, 97, 161302, 2006].
a. Focus of PhD. work:
My primary research interest is in soft condensed matter physics. During my PhD. years my focus has been on understanding the dynamical mechanism behind glass formation. Glass is a state between a liquid and a crystalline solid. It is a disordered solid which can ``flow" over very long time scales. My interest was in understanding how the addition of a second component in a one-component liquid affects the rate of glass formation.
b. Further Research Interests:
Since my PhD. years my research interests have broadened. I have done research on freezing of colloids in the presence of laser beams, Brownian motion at absolute zero, optics, and have also studied loss of coherence at the absolute zero of temperature.
I have studied the distribution of solid angles
(Refs.6,15) in a random walk on a sphere. This study was motivated by
the problem of depolarisation which occurs when light is elastically
scattered in a random medium. The same problem also comes up in the
distribution of Berry phases for a random Hamiltonian and the diffusion
of fluorescent molecules on the surface of a spherical micelle. The
methods developed in this study have a natural application in polymer
physics, which is my present interest.
As I mentioned earlier J. Samuel and I have
worked on a theoretical analysis of elasticity of biological polymers
motivated by an
analogy with depolarized light scattering. The methods developed in Refs.(6,15) can be adapted to produce a complete and exact solution of the Worm Like Chain model (WLC) for semiflexible polymers. This simple model captures much of the physics of the real system with just two parameters. Experiments on single DNA molecules are being carried out in the RRI in Prof. Shivashankar's lab. I have had an opportunity to interact closely with experimentalists and theorists working in this field at the Raman Research Institute. I intend to continue on an ongoing project (in collaboration with Joseph Samuel and Abhishek Dhar) to work out all the predictions of the Worm Like Chain (WLC) model. Such a study would be of crucial importance in constructing refinements of the model to get better agreement with experimental data.
We are also looking into the possibility of
some qualitatively interesting features
that have come out of Abhishek Dhar and Debashish Chaudhury's simulations, which have
been corroborated by our (J. Samuel and S. Sinha) theoretical work in this area.
We have had some preliminary discussions with V. A. Raghunathan, Y. Hatwalne and Abhishek Dhar.
Abhishek Dhar and I have been collaborating on
experiments involving vibrating mustard seeds at the Theorists'
RRI. This is a scaled up `Brownian motion' experiment and we are interested in looking at structural correlations in such systems.
Such experiments throw up many interesting issues - in what way does inelastic collisions in such systems
affect say `cage' formations in a dense granular system ? How does fluctuation-dissipation theorem work in
such a system and so on.
Onset of shear waves in a Bacterial Bath:
In recent years there have been experiments probing
`Brownian Motion' of
spheres in bacterial baths . These experiments point
to a crossover from superdiffusive to diffusive
behavior of the mean-square
displacement of the polysterene beads suspended in a bacterial bath.
This effect is similar to ballistic to diffusive transition in passive
Brownian systems where the borderline for such a transition is given by
the viscous damping time , which for a polysterene
bead of diameter 10 micron is about 10 micro sec. However, in the case
of an active bacterial bath one notices that such a transition takes
place at a time of about 2 sec .
To sum up, one of the key observations coming out of
these experimental studies is the emergence of a time scale and a
corresponding length scale in the Brownian motion of a polysterene bead
suspended in an active bacterial bath. The time at which this crossover takes place increases
with the increase in the density n of the bacterial bath, indicating the appearance of solid-like ordering over
length scales of the order of 10 micron.
In a simple dense liquid such ordering takes place on molecular length scales. In the present experiments the `liquid'
under consideration is an active medium of biological origin. Nonetheless, one
can import some of the ideas from passive liquids to understand certain aspects of
the dynamics of such a bath. In particular, I am focussing on the fact that
such a structural ordering in the bacterial bath would indicate the appearance of a shear
wave on length scales of the order of 10 micron. This is the
focus of my present theoretical study which has experimental implications.
At the theorists' lab at RRI Abhishek Dhar and
I have been looking at a scaled up `Brownian Motion' experiment, which
described in the Granular Materials section. We also intend to look at scaled up ` entropy driven motion of DNA' experiments
using chains and nylon threads- These experiments, apart from demonstrating conceptual issues in statistical mechanics,
throws up challenging research level questions which we intend to look into.
I have had experience in teaching undergraduate level Classical Mechanics and Electromagnetism at Syracuse University. I have also been a grader in a graduate level Solid State Physics Course at Syracuse. I have given lectures on Hydrodynamics and Mode-Coupling theory to PhD. students at the Indian Institute of Science. During my stay at the Raman Research Institute, I have been involved in presenting elementary optics to school children with practical demonstrations involving lasers.
During the past few years I had worked towards developing educational CDroms and web-based tutorials in Mathematics and Physics at the pre-university and undergraduate levels as part of software companies like SSI, egurucool.com and Hotmath Inc. USA. I have written educational articles combining Mathematics and Physics for the Children's section in `Deccan Herald' and also written articles for science education journals such as `Resonance' and `Jantar Mantar'.
Selected List of Publications:
Motion at Absolute Zero,"
Supurna Sinha and R. D. Sorkin,
Physical Review B, 45, 8123 (1992).
Theory of the Stress-Tensor Autocorrelation Function of a Dense Binary
Supurna Sinha and M. C. Marchetti ,
Physical Review A, 46, 4942 (1992).
of a Dense Mixture," Supurna Sinha,
Physical Review E, 49, 3504 (1994).
Motion and Magnetism "
S. Sinha and J. Samuel, Rapid Communication in Physical Review B ,
5. ``Effect of
Fluctuations on Laser Induced
Freezing of Colloidal Suspensions"
J. Chakrabarti and S. Sinha,
Journal de Physique II , 7, 729 (1997).
6. ``Decoherence at
Supurna Sinha, Physics Letters A, 228, 1 (1997).
of Semiflexible polymers,''
J. Samuel and S. Sinha Physical Review E, 66, 05801 (R)
(2002).[Selected for the Virtual Journal Of Biological Physics Research]
8. ``Onset Of
Shear Waves In A Bacterial Bath: A Novel
Effect,'' Supurna Sinha, Fluctuation and Noise
Letters, 3, L373 (2003).
Distribution of Stretched Polymers,''
Supurna Sinha, Physical Review E, 70, 011801 (2004).
[Selected for the Virtual Journal Of Biological Physics Research]
``Inequivalence Of Ensembles in Single Molecule
Measurements'', S. Sinha and J. Samuel,
Physical Review E , 71, 021104 (2005).
[Selected for the Virtual Journal Of Biological Physics Research, March 1
buckling-induced folding and rotation
of red blood cells in an optical trap,'' A.
Ghosh, Supurna Sinha, J. Samuel, J. A. Dharmadhikari,
A. K. Dharmadhikari, S. Sharma and D. Mathur;
[ Phys. Biol. Vol. 3, 67-73 (2006)]. ;
(this work has been highlighted in a coverage in ``New Scientist".
Zeeya Merali, 2513, 20 August 2005).
and the Cosmological
Constant," Joseph Samuel and Supurna Sinha,
Physical Review Letters, 97, 161302 (2006).
in Grain Mixtures:
An Extended Hydrodynamic Approach,"
Fluctuation and Noise Letters, 7, L163 (2007).
List of Publications : Technical papers
1. ``Short Wavelength Collective Modes in a Binary Hard Sphere Mixture," (M. C. Marchetti and S. Sinha), Physical Review A 41 3214 (1990). This paper has been reprinted in a special web based collection of papers on thermal and statistical physics under the heading `Mode-Coupling Theory'.
2. ``Sound Propagation Gap in Fluid Mixtures", (S. Sinha and M. C. Marchetti), Physical Review A 42 5015 (1990).
3. ``Brownian Motion at Absolute Zero," (S. Sinha
and R. D. Sorkin), Physical Review B 45 8123 (1992).
4. ``Mode-Coupling Theory of the Stress-Tensor
Autocorrelation Function of a Dense Binary Fluid Mixture." (S. Sinha
M. C. Marchetti), Physical Review A 46 4942 (1992).
5. ``Dynamic Structure Factors of a Dense Mixture." ,
Physical Review E49 3504 (1994).
6. ``Brownian Motion and Magnetism " (S. Sinha and
J. Samuel),Rapid Communication in Physical Review B B50
7. ``Effect of Fluctuations on Laser Induced
Freezing of Colloidal Suspensions" (J. Chakrabarti and S. Sinha), Journal
de Physique II 7 729 (1997).
8. ``Short Wavelength Collective Modes in a Binary
Hard Sphere Mixture," (M. C. Marchetti and S. Sinha), Bulletin of
the American Physical Society 35 268 (1990).
9. ``Collective Dynamics in a Dense Binary Mixture,"
S. Sinha, Europhysics Conference Abstracts 14 C (1990)
10. ``Large Mode-Coupling Effects in a Dense
Mixture," (S. Sinha and M. C. Marchetti), Bulletin of the American
Physical Society 37 707 (1992)
11. ``Quantum Brownian
Motion", S. Sinha and R.D. Sorkin) Bulletin of the American
Society 37 650 (1992).
12. ``Decoherence at Absolute Zero'' , S.
Sinha, Physics Letters A228 1 (1997).
13. ``Thomas Rotation and Polarised Light: A
non-Abelian Geometric Phase in Optics" (J. Samuel and S. Sinha), Pramana-J.
Phys. 48 969 (1997).
14. `` Four-photon interference: a realizable
experiment to demonstrate violation of EPR postulates for perfect
correlations" (P. Hariharan, J. Samuel and S. Sinha),Journal of
Optics B : Quantum and Semiclassical Optics1 199 (1999).
15. ``Brownian motion on a sphere:distribution of
solid angles" (M. M. G. Krishna , J. Samuel and S. Sinha) Journal
Physics A (Mathematical and General)33 5965 (2000)
16. ``Elasticity of Semiflexible polymers''
in Grain Mixtures:
An Extended Hydrodynamic Approach,"
Fluctuation and Noise Letters, 7, L163 (2007).
Some conferences attended:
1. Conference on Fluid Dynamics, Buffalo, 1987.
2. Rutgers Conference on Statistical Physics, Rutgers, 1988 and 1990.
3. Ist Conference on Liquid Matter, Lyon, 1990.
4. American Physical Society Meeting, Indiannapolis, March 1992.
5. Conference on Common Problems in Condensed Matter
and Low-dimensional Field Theory, Madras, 1993.
6. Indo-French Conference on Mathematical Methods
for Partial Differential Equations, Bangalore, 1994.
7. SERC School on Optics, Madras, 1995.
8. International Conference on Liquid Crystals,
9. International Conference on Liquid Crystals, Bangalore, 2002.
10. International Workshop On Single Molecule Biophysics, NCBS, Bangalore, Jan 4-15, 2004.
11. Workshop on Biopolymers at ICTP, Trieste (May 25, 2005 - June 3, 2005).