• Tuesday 2 February 2010 at 10.15 in E204: Sean Nowling (University of Helsinki)
  Solitons in Holographic Superfluids
  Abstract: The gauge/gravity duality provides a new set of tools for exploring the physics near 2+1 dimensional quantum critical points. In many highly quantum states of matter, soliton configurations yield clues about the physics of both large and small length scales. I will review a holographic model for a relativistic superfluid. I will then discuss dark soliton and vortex solutions supported by this superfluid. (arxiv:0911.1866 and 0912.4280)
  
  
• Tuesday 9 February 2010 at 10.15 in E204: Jyrki Piilo (University of Turku)
  Open systems with memory
  Abstract: The theory of open quantum systems describes the dynamics of a system of interest interacting with its environment. When the environment has nontrivial structure, the system dynamics exhibits non-Markovian memory effects. We have recently developed a non-Markovian quantum jump description for such systems. The basic idea and insight is that the negative rates associated to non-Markovian quantum processes allow the system undo an event which happened earlier. In the more general stochastic process framework, this leads to the manifestation of memory as certain correlations between the realizations of the stochastic process. We conclude by discussing how one can define a measure for memory based on quantifying the information flow between the system and its environment. Essentially, in non-Markovian systems the information flow between the system and the environment gets temporarily reversed, and the system regains part of the information that it earlier leaked to the environment. In other words, in Markovian systems the distinguishability between any pair of states always decreases with time while in non-Markovian systems the distinguishability temporarily increases due to the memory. (See http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.103.210401).
  
  
• Thursday 11 February 2010 at 10.15 in A315: W. Horowitz (Ohio State University)
  Jet quenching, perturbative QCD and AdS/CFT
  Abstract: The basic theoretical and experimental tools of heavy ion phenomenology are reviewed, including the recent application of AdS/CFT to bulk QCD physics. Jet suppression is argued to be a unique tool for studying collective degrees of freedom for the problem. Paying special attention to high momentum probes, we discuss the qualitative successes of both perturbative QCD and AdS/CFT and propose novel experimental observables for falsifying one or both sets of calculations. The extension of AdS heavy quark drag to both hot and cold nuclear matter, giving greater confidence in the universality of those results, is presented. Time permitting, the assumptions underpinning the pQCD derivations will be discussed leading to quantitative estimates of a systematic theoretical uncertainty for perturbative predictions in jet quenching.
  
  
• Tuesday 16 February 2010 at 10.15 in E204: Marco Panero (ETH Zürich)
  Hot, colorful and strongly interacting
  Abstract: The gauge/gravity correspondence developed in String Theory provides powerful analytical techniques to study strongly interacting systems, and is hoped to eventually lead to a theoretical description of the nearly inviscid, strongly coupled fluid produced in heavy ion collision experiments. However, most of the predictions that have been worked out in this approach rely on the mathematical simplifications taking place when the rank of the gauge group is infinite, and it is not obvious whether they can also be accurate for the physical case of a quark-gluon plasma with N = 3 colors. In this talk, I present lattice simulations of SU(N) gauge theories with 3, 4, 5, 6, and 8 colors, and their extrapolation to the large-N limit. The results reveal that the equation of state is only mildly dependent on N, and that the equilibrium properties of the strongly interacting plasma can be successfully described by gauge/gravity models. Furthermore, for all gauge groups investigated, the trace anomaly appears to exhibit a characteristic dependence on the temperature, perhaps induced by contributions of non-perturbative origin. The implications of these results, as well as some future research lines, are pointed out. (arXiv:0907.3719)
  
  
• Tuesday 9 March 2010 at 10.15 in E204: Janne Alanen (University of Helsinki)
  TBA
  Abstract: TBA (arXiv:0912.4128)
  
  
• Tuesday 23 March 2010 at 10.15 in E204: Valery Nesvizhevsky (Institute Laue-Langevin, Grenoble)
  Gravitational and centrifugal quantum states of neutrons and fundamental short-range interactions
  Abstract: The "whispering gallery" effect is known since ancient times for sound waves in air, later in water, more recently for electromagnetic waves of a broad range: radio, optics, Roentgen etc. It consists of wave localization near a curved reflecting surface. It is expected for waves of various nature, for instance, for atoms and neutrons. For matter waves it would include a new feature: a massive particle would be settled in quantum states, with parameters depending on its mass. Here, we present for the first time the quantum whispering gallery effect for cold neutrons. Deeply bound whispering gallery states are long-living and weakly-sensitive to surface potential; highly excited states are short-living and very sensitive to the wall potential shape.
  This phenomenon provides an example of an exactly solvable problem analogous to the "quantum bouncer". It is complementary to the recently discovered gravitationally bound quantum states of neutrons. In relation to this analogy we present also the GRANIT project aiming at improvement of accuracy of measurement of the quantum states parameters by several orders of magnitude, taking advantage of long storage of ultracold neutrons at specular trajectories and resonance transitions between the gravitationally bound quantum states of neutrons.
  These two experiments are motivated by searches for short-range interactions (spin-independent and spin-dependent ones), by studying the interaction of a quantum system with a gravitational field, by searches for extensions of the Standard model, by the unique possibility to check the equivalence principle for an object in a quantum state and by studying various quantum optics effects. These two phenomena provide the first direct demonstration of the weak equivalence principle for a massive particle in a pure quantum state.

Seminars in 2007 , in 2008 , in 2009 . For talks earlier in 2010, see page source.

Hopefully the up to one hour long seminar/colloquium will be understandable to a wide audience.
Contacts: Keijo Kajantie (keijo kajantie at helsinki fi) [department / HIP seminar],
Vappu Reijonen (vappu reijonen at helsinki fi) [cosmo seminar]