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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 sali 0.03, ul. Pasteura 5 o godzinie 16:30

prof. Szymon Malinowski (Instytut Geofizyki Wydziału Fizyki UW)

Historia współczesnej fizyki klimatu i globalne ocieplenie: skąd wiemy jak działa klimat i jak rozumieć prognozy jego zmian?

Już w 1896 roku Svante Arrhenius opublikował całkiem dobre oszacowania zmiany temperatury naszej planety przy podwojeniu koncentracji CO₂ w atmosferze. W 1965 roku grupa naukowców amerykańskich w oficjalnym dokumencie wysłanym do prezydenta USA Lyndona B. Johnsona ostrzegała przed niebezpieczną zmianą klimatu spowodowaną niekontrolowanym wzrostem koncentracji gazów cieplarnianych w atmosferze. Na jakiej podstawie powstały te prace? Czy ich prognozy się sprawdziły? Co dalej z klimatem? Jak dziś powstają prognozy zmian klimatu, gdzie są ich mocne i słabe punkty? O tym opowiem podczas konwersatorium.

Przed konwersatorium, od godz. 16.00, zapraszamy jak zwykle na kawę i nieformalne dyskusje do holu przed salą 0.03.
Barbara Badełek
Jan Kalinowski
Marek Pfützner
Wojciech Satuła
Jan Suffczyński

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Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30

Prof. Jan Zaanen (Instituut-Lorentz for Theoretical Physics, Leiden University, The Netherlands)

The string theory – condensed matter flirtation: an eyewitness account

A quake is rumbling through the core of physics: the empiricisms of condensed matter physics and the mathematics of string theory appear to have some deep relations. For the initiated this has an unusually strong allure, but since this cocktail involves some of the most impenetrable areas of physics it is not easy to communicate the excitement to the community at large. I will attempt to get some of it across by telling the story from the perspective of a condensed matter theorist who learned string theory only quite recently. How string theory evolved from a reductionist’s enterprise into some modern incarnation of statistical physics, equipped with general relativity turbo’s and quantum information boosters in the form of the “AdS/CFT” holographic duality. How the universality of general relativity turned into a classification method for phases of matter, including new forms of “quantum” matter characterized by dense quantum entanglements on the macroscopic scale. How the latter reveal highly unusual traits having eerie resemblances with the mysterious experimental observations, with as highlight the famous linear resistivity measured in the strange metal phase of the high Tc supercondcutors.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30

dr István Rácz (Instytut Fizyki Teoretycznej Wydziału Fizyki UW)

Evolution in spaces of Euclidean signature?

We all learn from basic courses in physics that concepts like time or evolution are something to do with the hyperbolic or parabolic character of our equations. Hyperbolicity in many circumstances may also straightforwardly be traced back to the Lorentzian signature of the metric of the underlying spacetime. In this seminar I intend to provide some evidences–using specific examples of physical interest–demonstrating that, on contrary to intuition, evolutionary methods may also play important role in spaces of Euclidean signature.Interesting questions arise then concerning the appearance of an abundance of time functions in spaces which had been considered to admit none.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30

Dr hab. Michał P. Heller (Albert Einstein Insitute; National Centre for Nuclear Research, Świerk)

Gravity, Quantum Fields and Information

The colloquium will discuss two recent developments at the intersection of high energy physics and quantum information science:

1) various geometrizations of entanglement entropy in scale-invariant quantum field theories and their role in encoding matter fields living in emergent dynamical geometry (based on 1509.00113 & 1606.03307);

2) an attempt to quantify the notion of complexity of quantum field theory states and their relation to volumes of holographic spacetime (based on 1707.08582).

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30

Dr hab. Piotr Sułkowski (Instytut Fizyki Teoretycznej Wydziału Fizyki UW)

What is quantum field theory?

The essence of the above title is the question mark. As stated in the Stanford Encyclopedia of Philosophy, "In contrast to many other physical theories there is no canonical definition of what Quantum Field Theory (QFT) is. Instead one can formulate a number of totally different explications, all of which have their merits and limits".
One important limitation of the current understanding of QFT is an unsatisfactory description of strongly coupled systems. In this talk I will discuss some attempts to formulate such a description, which – in certain simplified settings – revealed deep dualities between QFTs, intimate links between QFT and string theory, led to classification of certain classes of QFTs, etc. While these lessons so far have not led to an ultimate answer to the question of what QFT is, they indicate what features such an answer should involve.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30

Dr hab. Paweł Pietrukowicz (Obserwatorium Astronomiczne UW)

OGLE - 25 years of revolutionary discoveries

In 2017 the Optical Gravitational Lensing Experiment (OGLE) celebrates 25 years in operation. I will present the history and some technical aspects of the project and I will review the most important scientific discoveries that have a great impact on modern astrophysics.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30

Prof. dr Maria Daghofer (University of Stuttgart)

Correlations and topology in multi-orbital system

Electronic correlations have long been known to fundamentally affect a material's property. I will discuss situations, where they can induce topologically nontrivial electronic states. Interaction between itinerant carriers and localized spins on frustrated lattices can stabilize phases that are in many respects similar to a Landau level. If the bands are nearly flat, longer-range Coulomb repulsion can then induce states that are like lattice-analogs of fractional Quantum-Hall states, but do not require an external magnetic field. I will also discuss Mott insulators with spin-orbit coupling, effectively modeled with classical spins. The ground state has turned out to support a vortex lattice of topological defects, Z 2 vortices, whose density is determined by the strength of the spin-orbit coupling.

Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30

Dr hab. Rafał Demkowicz-Dobrzański (Instytut Fizyki Teoretycznej Wydziału Fizyki UW)

Ultraprecise measurements in the era of quantum information

In recent years, there is a growing interest in employing ideas andexperimental techniques most commonly associated with quantuminformation processing applications, such as quantum computing orquantum communication, to improve sensitivity of metrologicalprotocols. Advantages of utilizing squeezed states of light havealready been demonstrated in gravitational wave detectors, quantumion manipulation techniques, developed with quantum computingapplications in mind, have been employed in the so called quantumlogic spectroscopy, while NV centers have been used to performmagnetic field sensing with sensitivity enhanced thanks to the useof quantum error-correction techniques. The talk will discuss theserecent experimental advances as well as provide theoreticalfoundations laying behind them.