Soon: 3 seminars

Cond.Matt. & Stat.Mech.Section cm at
Mon Nov 19 14:50:02 CET 2012

INFORMAL SEMINAR on    Statistical Physics

Tuesday, 20 November    -    4:00 p.m.


Euler Lecture Hall,   ICTP Leonardo Building - terrace level


Tommaso BIANCALANI     ( The University of Manchester )


"Noise-induced metastability in biochemical networks"




With recent advances in experimental techniques, it is becoming increasingly clear that the dynamics of cellular biochemical reactions are subject to a great deal of noise.  This poses a significant challenge to our understanding of such systems, as it has been known for some time that the effects of noise may lead to substantial differences in the macroscopic behaviour.  Here, we report analytical progress on this problem made by studying a simple class of reaction networks whose dynamical behaviour is radically affected by intrinsic stochasticity in finite volume cells.  In particular, we show how networks of this type give rise to a separation of timescales between fast almost-deterministic oscillations and slow stochastic metastability.  Our class includes the influential Togashi-Kaneko (TK) reaction scheme, which has been found to undergo a noise-induced dynamical transition via numerical simulations.  Despite the importance of their work, a satisfactory analytic treatment of this effect has not been achieved in over a decade.  Here we provide such a treatment as an application of our theory.




Wednesday, 21 November   -   4:00 p.m.


SISSA, Santorio Building,    Room 128 (1st Floor)


F. BECATTINI      ( University of Florence )

"Thermodynamics and the quantum   stress-energy and spin tensor"




In this seminar we show that thermodynamics is sensitive to the existence of a fundamental spin tensor, predicted by extensions of general relativity.  In general, thermodynamics is not invariant by a change of the stress-energy tensor of a fundamental quantum field with a divergence transformation leaving the total energy, momentum and angular momentum unchanged. Among the quantities which are changed by such a transformation, there are densities at equilibrium with rotation and non-equilibrium ones like transport coefficients and total entropy.  Therefore, at least in principle, it could be possible to probe the existence of a spin tensor with a thermodynamics experiment.


SEMINAR on      Disorder and strong electron correlations

Thursday, 22 November -  11:30 a.m.


Luigi Stasi Seminar Room,  Leonardo Building - first floor


Yasir IQBAL     ( ICTP )

"Spin liquids in quantum antiferromagnetic models on  two dimensional frustrated lattices"




For many decades physicists have been searching for "hot'' enough playgrounds that can melt magnetic freezing even at extremely low temperatures, purely due to strong quantum fluctuations.  The resulting quantum paramagnetic phases of matter called spin liquids, do not spontaneously break any symmetries, possess quantum and topological orders, and consequently fall outside the paradigm of traditional condensed matter theory based on the Landau's Fermi liquid theory and Landau's theory of phase transitions.  Remarkably enough, the "deceptively'' simple spin-1/2 Heisenberg antiferromagnetic model, when put on the most frustrated lattice, the "kagome'' lattice, has been shown, both experimentally and theoretically to host such an exotic state.  I will present my research work dealing with the precise identification of this state, which is currently being debated very intensely. I will show, within fermionic slave particle approaches, that a certain "marginally'' stable spin liquid with a U(1) low energy gauge structure (so-called Dirac spin liquid) is remarkably robust to all known perturbations towards stable Z2 spin liquids and Valence-bond crystals, despite having strongly interacting gapless fermionic excitations down to zero energy.  Finally, using state-of-the-art numerical techniques such as the application of Lanczos steps on variational wave functions combined with Green's function Monte Carlo technique, I will show that such an exotic algebraic spin liquid can in fact exist as a real physical spin liquid ground state.


1.) Phys. Rev. B 83, 100404 (2011) - Y. Iqbal, F. Becca, and D. Poilblanc.

2.) Phys. Rev. B 84, 020407 (2011) (Editor's suggestion) - Y. Iqbal, F. Becca, and D. Poilblanc.

3.) New J. Phys 14, (in press) (2012); arXiv: 1203.3421 - Y. Iqbal, F. Becca, and D. Poilblanc.

4.) arXiv: 1209.1858 [cond.mat] (2012) - Y. Iqbal, F. Becca, S. Sorella, and D. Poilblanc.

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