Wydział Fizyki UW > Badania > Seminaria i konwersatoria > Konwersatorium im. Leopolda Infelda (do roku 2017/18)

Konwersatorium im. Leopolda Infelda

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Zapraszamy do Nowej Auli (425), ul. Hoża 69 o godzinie 15:30

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Zapraszamy do Nowej Auli (425), ul. Hoża 69 o godzinie 15:30

Prof. Abhay Ashtekar (Institute for Gravitation and the Cosmos, Penn State)

The Big Bang and the Quantum

General relativity ushered-in the era of modern cosmology. The resultingFriedmann models ---and perturbations thereof--- have enjoyed anastonishing degree of observational success. But general relativity isincomplete because it ignores the quantum nature of gravity. It predictsthat space-time comes to an end and physics stops at singularities. Recentdevelopments in non-perturbative quantum gravity have shown that thesepredictions cannot be trusted. Specifically, quantum geometry effects canresolve singularities, thereby opening new vistas. My talk will coverthese foundational issues and discuss implications of the new Planck scalephysics near the Big Bang.

Zapraszamy do Nowej Auli (425), ul. Hoża 69 o godzinie 15:30

Dr Zbigniew Idziaszek (IFT UW)

Ultracold gases of polar molecules

Ultracold polar molecules open new prospects for quantum gases withlong-range and anisotropic interactions and can find applications inquantum information science and in precision measurement. Recentexperiments reported production of relatively dense gases or lattices ofultracold molecules in their rotational and vibrational ground state. Itis essential to understand elastic, inelastic and reactive collisions ofsuch molecules in order to control and utilize them effectively. In thistalk I will briefly review recent advances in this field, and I willpresent a method based on the concept of a quantum defect to modelcollisions of ultracold molecules. In the case of highly reactivemolecules this method predicts universal reaction rates that can becalculated analytically from a knowledge of the long-range part of theinteraction potential.

Zapraszamy do Nowej Auli (425), ul. Hoża 69 o godzinie 15:30

dr So Takei (Max Planck Institute for Solid State Research, Stuttgart)

Nonequilibrium quantum criticality in single- and bi-layer itinerant electron ferromagnets

A scaling theory is presented for quantum criticality in an open(coupled to reservoirs) itinerant electron ferromagnet, withnonequilibrium drive provided by current flow across the system.Both departures from equilibrium at conventional (equilibrium)quantum critical points and the physics of phase transitionsinduced by the nonequilibrium drive are studied. The theory isextended for a coupled bilayer system of itinerant electronferromagnets in which one layer is driven out of equilibrium bycurrent flow along the system. We discuss the interplayof two different dynamical scales that arises in the presence oftwo bosonic fields, which are related to the magnetizationfluctuations of the two layers. In both systems, the resultsare presented for order parameters with Ising symmetry.

Zapraszamy do Nowej Auli (425), ul. Hoża 69 o godzinie 15:30

prof. dr hab. Bohdan Grządkowski (IFT UW)

Non-Supersymmetric New Physics at the Dawn of LHC

After introduction of the Standard Model (SM) for electro-weak interactionsI will discuss its drawbacks and possible improvementsthat could be tested at the Large Hadron Collider.I will focus on extensions of the scalar sector and on extra dimensionalmodels including large extra dimensions (ADD), the Randall-Sundrum modeland the gauge-Higgs unification

Zapraszamy do Nowej Auli (425), ul. Hoża 69 o godzinie 15:30

Prof. Gerhard Huisken (Max Planck Institute for Gravitational Physics, Albert Einstein Institute)

Geometric concepts for the mass in General Relativity

It is a major aim of mathematical relativity tofind and describe natural geometric structures that modelclassical physical concepts for isolated gravitating systems, such asmass, center of mass and momentum. The lecture explainshow suitable foliations of space-time and geometric variationalproblems such as the isoperimetric inequality can be usedto define a useful and geometrically invariant concept forthe total mass of a system. The lecture also describes howelliptic and parabolic systems of geometric PDEs are used tojustify these concepts in the context of Einsteins equations.

Zapraszamy do Nowej Auli (425), ul. Hoża 69 o godzinie 15:30

prof. dr hab. Edward Malec (Uniwersytet Jagielloński)

General Relativistic versus Newtonian: a universality in radiation hydrodynamics

We compare Newtonian and general relativistic descriptions of thestationary accretion of selfgravitating fluids onto compact bodies.Spherical symmetry and thin gas approximation are assumed. Luminositydepends, amongst other factors, on the temperature and thecontribution of gas to the total mass, in both -- general relativistic($L_{GR}$) and Newtonian ($L_N$) -- models. We discover a remarkableuniversal behaviour for supersonic flows: the ratio of respectiveluminosities $L_{GR}/L_N$ is independent of the fractional mass of thegas and depends on asymptotic temperature. It is close to 1 in theregime of low asymptotic temperatures and can grow by one order for hightemperatures. These conclusions are valid for a wide range of polytropicequations of state.

Zapraszamy do Nowej Auli (425), ul. Hoża 69 o godzinie 15:30

dr Rafał Demkowicz-Dobrzański (IFT UW)

Estimation and naughty quantum states - why it is so hard to make them cooperate?

Quantum states offer broader possibilities for performing precisemeasurements of time, length or direction, then classical methods. Inorder to benefit from this potential one needs to overcome variousdifficulties such as non-perfect distinguishability of non-orthogonalquantum states and their susceptibility to decoherence.Once this difficulties are overcome, quantum states offer betterprecision than that offered by classical methods.

Zapraszamy do Nowej Auli (425), ul. Hoża 69 o godzinie 15:30

prof. Catherine Meusburger (Department of Mathematics, University of Hamburg)

Observables and geometry in (2+1)-gravity

Gravity in 2+1 dimensions serves as a toy model for higher dimensional (quantum) gravity. The theory is closely related toChern-Simons gauge theory and allows for an explicit parametrisation of its phase space and rigorous quantisation. We discuss the relation between spacetime geometry and the observables of the theory. In particular, we show that Wilson loop observables act as the generators of the two fundamental transformations that change the geometry of spacetimes.

Zapraszamy do Nowej Auli (425), ul. Hoża 69 o godzinie 15:30

prof. Maciej Lewenstein (The Institute of Photonic Sciences, Barcelona)

Ultracold atoms in artificial gauge fields

I will present a review of recent developments of a new trend in the physics of ultracold atoms, that concerns studies of the behavior ofquantum degenerate atomic clouds in presence of quantum gauge fields. I will discuss various methods of generating such artificial gaugefields, with special emphasis on the non-Abelian ones. I will then discuss few examples of effects and phenomena expected to occur insuch non-Abelian gauge fields. These include: anomalous quantum Hall effect, emergence of Dirac fermions, novel types of topologicalisolators, etc.

Zapraszamy do Auli (425), ul. Hoża 69 o godzinie 15:30

Prof. Lars Bergstrom (The Oskar Klein Centre for Cosmoparticle Physics, Physics Department, Stockholm University)

Dark Matter - where do we stand?

The hunt for the identity of the particle responsible for five times more mass in the Universe than ordinary matter is getting increasinglyintensified. New hints - or false leads? - have recently appeared in the energy distribution of electrons, positrons, and gamma-rays. Dark matter annihilating in our galactic halo of dark matter is one of several possibilities.

In this talk, we will briefly review the history of the dark matter problem, and explain why the scientific community is more and moreconvinced that dark matter exists. Methods of detection will be summarized, and recent claims of detected signals discussed.

Zapraszamy do Auli (425), ul. Hoża 69 o godzinie 15:30

Prof. Dieter Vollhardt (Center for Electronic Correlations and Magnetism, University of Augsburg, Germany)

Superfluid Helium-3: From very low Temperatures to the Big Bang

Since their discovery in 1971 the superfluid phases of Helium-3 have proved to be the ideal testing ground for many fundamental concepts ofmodern physics. Phenomena such as Cooper pairing, macroscopic quantum coherence, spontaneous breaking of unusual symmetries, and the formation of exotic topological defects are not only an important enrichment of the physics of condensed matter, but also provide important links to particle physics and the structure of the early universe. These discoveries where acknowledged by the Nobel prizes of 1996 and 2003. In my colloquium talk I will give a simple introduction into the physics of superfluid Helium-3.

Zapraszamy do Sali Dużej Doświadczalnej (SDD), ul. Hoża 69 o godzinie 16:30

prof. dr hab. Miroslaw Karpierz (Wydział Fizyki Politechniki Warszawskiej)

Światłowody; Nagroda Nobla z fizyki 2009

Przedstawiona zostanie historia odkryć i badań światłowodów, zwieńczona przyznaniem 1/2 Nagrody Nobla z fizyki w 2009 roku.W referacie przedstawione zostaną głowne właściwości światłowodow, dzięki którym są one obecnie powszechnie wykorzystywane.Trudno sobie bez nich wyobrazić współczesną telekomunikację, ale też są niezbędne w wielu innych systemach i układach optycznych.Przedstawione zostaną również obecne kierunki badań w zakresie światłowodów, w szczególności związane ze światłowodami fotonicznymi i mikrostrukturalnymi.

Zapraszamy do Auli (425), ul. Hoża 69 o godzinie 15:30

dr hab. Zygmunt Patyk (IPJ)

Własności cieżkich jonów wodoro- i helo-podobnych

Omówię badania cieżkich jonów wodoro- i helo-podobnych prowadzone w GSI-Darmstadt. Jony te są narzędziem badawczym elektrodynamiki kwantowej (efekt Lamba), struktury jądra atomowego (pomiar masy i momentu magnetycznego) oraz oddziaływan słabych (wychwyt elektronu i rozpad beta). Neutralne oddziaływania słabe pomiędzy elektronami a jądrem atomowym prowadzi do istnienia elektronowych stanów o nieokreślonej parzystości, np. w jonach He-podobnych. Badania teoretyczne znacznie upraszcza niewielkaliczba elektronów występująca w tych jonach.

Zapraszamy do Auli (425), ul. Hoża 69 o godzinie 15:30

prof. dr hab. Jerzy Lewandowski (IFT UW)

Loop Quantum Gravity and Spin Foam Models

This lecture will provide a bird's eye view of the background independent quantum approach to Eistein's gravity known as loop quantum gravity. The methodology of the theory and the present status will discussed. Several puzzling examples, interesting on their own, will be presented.