A5074250605- Theoretical and Computational Physics
- Quantum Electrodynamics and Casimir Effect
- Advanced Thermodynamics and Statistical Mechanics
- Stochastic processes and statistical mechanics
- Material Dynamics and Properties
- Thermal Radiation and Cooling Technologies
- Mechanical and Optical Resonators
- Physics of Superconductivity and Magnetism
- Micro and Nano Robotics
- Force Microscopy Techniques and Applications
- Evolution and Genetic Dynamics
- Electrostatics and Colloid Interactions
- T-cell and B-cell Immunology
- HIV Research and Treatment
- Statistical Mechanics and Entropy
- Protein Structure and Dynamics
- Monoclonal and Polyclonal Antibodies Research
- Experimental and Theoretical Physics Studies
- Lipid Membrane Structure and Behavior
- Cosmology and Gravitation Theories
- Advanced Materials and Mechanics
- Quantum many-body systems
- Diffusion and Search Dynamics
- Immune Cell Function and Interaction
- Complex Network Analysis Techniques
Massachusetts Institute of Technology
2015-2024
Middlebury College
2022
Istituto Nazionale di Fisica Nucleare, Sezione di Napoli
2022
IIT@MIT
1998-2021
Harvard University
1984-2013
Ragon Institute of MGH, MIT and Harvard
2013
Moscow Institute of Thermal Technology
1995-2013
University of California, Santa Barbara
1990-2009
Harvard–MIT Division of Health Sciences and Technology
2007-2008
Johannes Gutenberg University Mainz
2007
A model is proposed for the evolution of profile a growing interface. The deterministic growth solved exactly, and exhibits nontrivial relaxation patterns. stochastic version studied by dynamic renormalization-group techniques mappings to Burgers's equation random directed-polymer problem. exact scaling form obtained one-dimensional interface in excellent agreement with previous numerical simulations. Predictions are made more dimensions.
The Burgers equation is the simplest nonlinear generalization of diffusion equation. We present a detailed dynamical renormalization-group analysis this subject to random noise. noise itself can be product another stochastic process and hence allowed have correlations in space and/or time. In dimensions higher than critical ${d}_{c}$ weak strong lead different scaling exponents, while for d${d}_{c}$ any amount relevant resulting strong-coupling behavior. absence temporal we find two regimes...
The static Casimir effect describes an attractive force between two conducting plates, due to quantum fluctuations of the electromagnetic (EM) field in intervening space. Thermal correlated fluids (such as critical mixtures, super-fluids, liquid crystals, or electrolytes) are also modified by boundaries, resulting finite-size corrections at criticality, and additional forces that affect wetting layering phenomena. Modified EM can account for ``van der Waals'' interaction spheres, have...
Directed polymers subject to quenched external impurities (as in a polyelectrolyte gel matrix) are examined analytically, and numerically. Transverse fluctuations $|\mathrm{x}|$ scale with the length $t$ of polymer as $|\mathrm{x}|\ensuremath{\sim}{t}^{\ensuremath{\nu}}$. In all dimensions, for sufficiently strong disorder, $\ensuremath{\nu}$ can be different from random-walk value \textonehalf{}. Extensive numerical simulations two, three, four dimensions fact suggest superuniversal...
Our understanding of the ``long range'' electrodynamic, electrostatic, and polar interactions that dominate organization small objects at separations beyond an interatomic bond length is reviewed. From this basic-forces perspective, a large number systems are described from which one can learn about these organizing forces how to modulate them. The many practical harness nanoscale then surveyed. survey reveals not only promise new devices materials, but also possibility designing them more...
We develop an exact method for computing the Casimir energy between arbitrary compact objects, either dielectrics or perfect conductors. The is obtained as interaction multipoles, generated by quantum current fluctuations. objects' shape and composition enter only through their scattering matrices. result when all multipoles are included, converges rapidly. A low frequency expansion yields a series in ratio of size to separation. As example, we obtain this two dielectric spheres full at...
Our investigation of knotted structures in the Protein Data Bank reveals most complicated knot discovered to date. We suggest that occurrence this a human ubiquitin hydrolase might be related role enzyme protein degradation. While knots are usually preserved among homologues, we also identify an exception transcarbamylase. This allows us exemplify function proteins and how they may have been created.
We derive a microscopic expression for the mechanical pressure P in system of spherical active Brownian particles at density ρ. Our exact result relates P, defined as force per unit area on bounding wall, to bulk correlation functions evaluated far away from wall. It shows that (i) P(ρ) is state function, independent particle-wall interaction; (ii) interactions contribute two terms one encoding slow-down drives motility-induced phase separation, and other direct contribution well known...
We give a comprehensive presentation of methods for calculating the Casimir force to arbitrary accuracy, any number objects, shapes, susceptibility functions, and separations. The technique is applicable objects immersed in media other than vacuum, nonzero temperatures, spatial arrangements which one object enclosed another. Our method combines each object's classical electromagnetic scattering amplitude with universal translation matrices, convert between bases used calculate object, but...
From proteins to chromosomes, polymers fold into specific conformations that control their biological function. Polymer folding has long been studied with equilibrium thermodynamics, yet intracellular organization and regulation involve energy-consuming, active processes. Signatures of activity have measured in the context chromatin motion, which shows spatial correlations enhanced subdiffusion only presence adenosine triphosphate. Moreover, motion varies genomic coordinate, pointing toward...
Motivated by recent studies of Bak, Tang, and Wiesenfeld [Phys. Rev. Lett. 59, 381 (1987); Phys. A 38, 364 (1988)], we study self-organized criticality in models ``running'' sandpiles. Our analysis reveals rich temporal structures the flow sand: at very short time scales, is dominated single avalanches. These avalanches overlap intermediate scales; their interactions lead to 1/f noise flow. We show that scaling this region a consequence conservation laws exhibited many examples...
We study the statistical mechanics of two-dimensional surfaces fixed connectivity embedded in $d$ dimensions, as exemplified by hard spheres tethered together strings into a triangular net. Without self-avoidance, entropy generates elastic interactions at large distances, and radius gyration ${R}_{G}$ increases ${(\mathrm{ln}L)}^{\frac{1}{2}}$, where $L$ is linear size uncrumpled surface. With self-avoidance grows ${L}^{\ensuremath{\nu}}$, with $\ensuremath{\nu}=\frac{4}{(d+2)}$ obtained...
Motivated by recent models of Bak, Tang, and Wiesenfeld we study dissipative transport in open systems. A simple continuum equation is constructed to describe fluctuations around a steady state flowing ``sandpile.'' The principle scale invariance self-similarity understood terms conservation law dynamics. dynamic renormalization-group calculation allows us determine various critical exponents exactly all dimensions.
We study the dynamics of passage a polymer through membrane pore (translocation), focusing on scaling properties with number monomers N. The natural coordinate for translocation is one side hole at given time. Commonly used models that assume Brownian this variable predict mean (unforced) time tau scales as N2, even in presence an entropic barrier. In particular, however, it takes free to diffuse distance order its radius by Rouse exponent larger than two, and should provide lower bound To...
We consider the passage of long polymers length N through a hole in membrane. If process is slow, it principle possible to focus on dynamics number monomers s one side membrane, assuming that two segments are equilibrium. The $s(t)$ such limit would be diffusive, with mean translocation time scaling as ${N}^{2}$ absence force, and proportional when force applied. demonstrate assumption equilibrium must break down for sufficiently (more easily forced), provide lower bounds by comparison...
We apply renormalization-group and Monte Carlo methods to study the equilibrium conformations dynamics of two-dimensional surfaces fixed connectivity embedded in d dimensions, as exemplified by hard spheres tethered together strings into a triangular net. A continuum description is obtained. Without self-avoidance, radius gyration increases \ensuremath{\surd}lnL , where L linear size uncrumpled surface. The upper critical dimension self-avoiding infinite. Their grows...
We find the exact Casimir force between a plate and cylinder, geometry intermediate parallel plates, where is known exactly, sphere, it at large separations. The has an unexpectedly weak decay approximately L/[H3 ln(H/R)] plate-cylinder separations H (L R are cylinder length radius), due to transverse magnetic modes. Path integral quantization with partial wave expansion additionally gives qualitative difference for density of states electric modes, corrections finite temperatures.
The fractional Laplacian operator -(-delta)(alpha/2) appears in a wide class of physical systems, including Lévy flights and stochastic interfaces. In this paper, we provide discretized version which is well suited to deal with boundary conditions on finite interval. implementation justified by appealing two models, namely, hopping particles elastic springs. eigenvalues eigenfunctions bounded domain are then obtained numerically for different conditions. Some analytical results concerning...
We present a detailed derivation of heat radiation, transfer, and (Casimir) interactions for $N$ arbitrary objects in the framework fluctuational electrodynamics thermal nonequilibrium. The results can be expressed as basis-independent trace formulas terms scattering operators individual objects. prove that radiation single object is positive, transfer (for two passive objects) from hotter to colder body. transferred also symmetric, exactly reversed if temperatures are exchanged. Introducing...
Broadly neutralizing HIV antibodies (bnAbs) are typically highly somatically mutated, raising doubts as to whether they can be elicited by vaccination. We used 454 sequencing and designed a novel phylogenetic method model lineage evolution of the bnAbs PGT121–134 found positive correlation between level somatic hypermutation (SHM) development neutralization breadth potency. Strikingly, putative intermediates were characterized that show approximately half mutation but still capable roughly...