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Wydział Fizyki UW > Badania > Seminaria i konwersatoria > Konwersatorium im. Leopolda Infelda (do roku 2017/18)
2015-06-11 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Prof. dr hab. Marek Demiański (Instytut Fizyki Teoretycznej Wydziału Fizyki UW)

The Cosmic Microwave Background Radiation at 50

Fifty years ago two radio engineers Arno Penzias and Robert Wilson serendipitously discovered the cosmic microwave background radiation. I will discuss the early attempts to determine its spectrum and briefly present results of the three subsequent satellite missions: COBE, WMAP and Planck. I will also present recent attempts to measure the level of polarization of the CMB radiation and restrictions that they impose on the models of very early evolution of the universe.
2015-05-21 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Prof. Patrick Dewilde (TUM-IAS, Germany)

Information, Communication and Computing: Past, Present and Future

The field of Information, Communication and Computing, sometimes abbreviated to ICC or ICT (with T=Technology) is characterized by a number of major discoveries mainly due to progressing insights in physics, mathematics and some other fields of science and technology.
In the presentation, I shall review the main past discoveries and discuss the present day playing field, to end with what I consider the main challenges for the future, trying, in particular, to motivate needed further developments in the key domains of science involved.

2015-05-15 (Piątek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 14:15  Calendar icon
Professor Aleksander Wolszczan (Pennsylvania State University)

Searching for radio flares from ultracool dwarfs and exoplanets

Detections of both coherent and incoherent, non-thermal radio emission from exoplanets represent a direct way to study their magnetic fields. For example, time-frequency mapping of radio flares generated by the cyclotron maser mechanism can be used to constrain the planet’s magnetic field topology and use it to infer the nature of the dynamo mechanism. In addition, because magnetic fields protect planets from stellar winds and flares, detecting and characterizing exoplanetary fields would obviously inform the investigations of planetary habitability. I will discuss the ongoing efforts to detect the flaring and the quiescent radio emission from the coolest brown dwarfs and giant exoplanets. In particular, I will present the most recent detections of flares from two T-type brown dwarfs with the Arecibo radio telescope. These detections suggest that the same should be possible for hot, young exoplanets such as the recently discovered HR8799 system.
2015-05-14 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Prof. Bertrand Delamotte (Pierre and Marie Curie University, Paris, France)

Scale invariance generically implies conformal invariance in three dimensions

A simple proof that scale invariance in scalar models generically implies conformal invariance in three (and four) dimensions is given. It relies on the very structure of the Wilson renormalization group that we first review. If time allows, a rigorous proof will also be given for the special case of the Ising (or ɸ4) model in all dimensions.
2015-04-16 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Prof. dr hab. Michał Horodecki (Wydział Matematyki, Fizyki i Informatyki Uniwersytetu Gdańskiego)

Thermodynamics as a resource theory

Recently, tools of quantum information have been applied to thermodynamics. The new approach allows to meaningfully define thermodynamics of microscopic systems out of equilibrium allowed to interact with a heat bath as well as to define ultimate, model independent limitations for thermodynamical processing.

Thermodynamics in such micro-regime becomes a resource theory, where the main question is whether a given state can be transformed into another state by means of some class of operations. The latter called Thermal Operations consists of arbitrary unitary operations that commute with the total bath-system Hamiltonian.

We will show, how the standard free energy splits in micro-system into at least two different free energies - one denoting the work needed to create a given state, and the other one - being the work that can be later recovered from the system.
We will also report on some recent advances, including thermodynamical processing of coherences.

The talk will be mostly based on the following articles:

Fundamental limitations for quantum and nanoscale thermodynamics, M. Horodecki & J. Oppenheim, http://arxiv.org/abs/1111.3834
http://www.nature.com/ncomms/2013/130626/ncomms3059/full/ncomms3059.html

The second laws of quantum thermodynamics Fernando Brandão, Michał Horodecki, Nelly Ng, Jonathan Oppenheim and Stephanie Wehner, http://arxiv.org/abs/1305.5278
http://www.pnas.org/content/112/11/3275.abstract

Towards fully quantum second laws of thermodynamics: limitations on the evolution of quantum coherences, Piotr Ćwikliński, Michał Studziński, Michał Horodecki, Jonathan Oppenheim,
http://arxiv.org/abs/1405.5029

2015-03-26 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Professor Sergio Bertolucci (CERN)

Present and future of Particle Physics: the role of Europe in the global context

The present situation of Particle Physics, with the recent exceptional experimental results, has shown the resilience of the Standard Model.
A similar situation is found in the field of Astrophysics, with the Planck data well described within the LambdaCDM.
But despite their success, we know that these models are incomplete, since they cannot explain a plethora of phenomena like dark matter, dark energy, baryon asymmetry, and fail to include gravity in a QFT frame.In this seminar I will describe how the world community, and in particular Europe, is gearing up to enter in this exciting period, which might lead us to a new vision of Nature.

2015-03-12 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Professor Neil Lambert (King's College London)

M-Theory and Hidden Spacetime in Quantum Field Theory

M-Theory arises as non-perturbative formulation of string theory and as such may be viewed as a complete quantum theory of particle physics, unified with gravity. However in this talk we will discuss predictions M-theory makes about the non-perturbative behaviour of quantum field theory. In particular we will discuss examples where there is a hidden extra dimension that opens up at strong coupling.
2015-02-26 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Dr Krzysztof Turzyński (Instytut Fizyki Teoretycznej Wydziału Fizyki UW)

Power spectrum of curvature perturbations in multi-field models of inflation

The inflationary paradigm is most simply realized by a model with a single, slowly rolling scalar field. As the cosmological data constraining inflation become more and more accurate, it is important to consider how this benchmark model is located in a theory space of more complicated models. To this end, I will present a few not-too-complicated examples of multi-field inflationary scenarios in which the relations between the observations and the model parameters can be quite different than in the simplest case.
2014-12-18 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Prof. dr hab. Iwo Białynicki-Birula (CFT PAN)

Quantum fluctuations of geometry in hot Universe

The fluctuations of spacetime geometries at finite temperature are evaluated within the linearized theory of gravity. These fluctuations will be described by the probability distribution of various configurations of the gravitational field. The gravitational field configurations are described by the linearized Riemann-Weyl tensor. The probability distribution has a foam-like structure, as intuitively argued by Wheeler. Prevailing configurations are those with the large changes of geometry at nearby points. Striking differences are found between the fluctuations of the electromagnetic field and the gravitational field
2014-12-04 (Czwartek)
Zapraszamy do sali nr 0.06 (parter) przy ul. Pasteura 5 o godzinie 15:30  Calendar icon
prof. dr hab. Tomasz Dietl (Instytut Fizyki PAN; Instytut Fizyki Teoretycznej UW; Instytut Zaawansowanych Badań Materiałowych (WPI-AIMR), Uniwersytet Tohoku, Sendai, Japonia)

Czy w Polsce można dokonywać znaczących odkryć naukowych?

Streszczenie referatu:

Współczesne oceny poziomu naukowego wydziałów czy instytutów, a także ośrodków akademickich, nie wykorzystują informacji o całkowitej liczbie publikacji czy odniesień do nich, ale budowane są na podstawie analizy kilku najważniejszych prac, które ukazują, czy dokonuje się tam przełomowych odkryć naukowych. Tezą odczytu jest przekonanie, że odpowiedź na postawione w tytule pytanie jest twierdząca, ale że liczba znaczących odkryć naukowych jest daleko za mała, nawet normując ją do poziomu finansowania nauki w Polsce. Korzystajac z doświadczeń czteroletniego udziału w pracach Rady Naukowej i Komitetu Sterujacego ERC przedstawię subiektywną ocenę przyczyn tej sytuacji oraz uwagi o możliwych środkach zaradczych.

Referat zostanie wygłoszony w ramach wspólnego posiedzenia konwersatoriów im. J. Pniewskiego i L. Infelda.

Zapraszamy!

Jacek Baranowski, Jan Kalinowski, Jerzy Kijowski, Czesław Radzewicz, Wojciech Satuła, Janusz Skalski

2014-11-27 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Prof. dr hab. Czesław Radzewicz (Instytut Fizyki Doświadczalnej Wydziału Fizyki UW)

Chemiczny Nobel 2014

Komitet Noblowski zdecydował, że tegoroczną nagrodę w dziedzinie chemii otrzyma 3 uczonych za opracowanie metod optycznej mikroskopii superrozdzielczej, dzięki którym można obrazować przedmioty mniejsze niż dopuszcza ograniczenie dyfrakcyjne. Trudno o lepszy dowód na hipotezę mówiącą, że żadna dziedzina nauki czy techniki nie jest skończona i zamknięta a jakościowa zmiana jest możliwa nawet tam gdzie rozwój trwa już kilkaset lat.W wykładzie spróbuję pokazać wagę mikroskopii superrozdzielczej, szczególnie dla nauk o życiu, na tle historycznym. Omówię podstawowe idee stojące za tym wynalazkiem; całość zilustruję kolorowymi obrazami rzeczy o rozmiarach mniejszych niż to wynika z formuły Abbe.

Referat zostanie wygłoszony w ramach wspólnego posiedzenia konwersatoriów im. L. Infelda i im. J. Pniewskiego

2014-11-06 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Dr Andrzej Dragan (Instytut Fizyki Teoretycznej Wydziału Fizyki UW)

Relativistic quantum information - a subjective overview

An observation that quantum effects can increase the efficiency of transmitting and processing information lead to the explosion of the field of quantum information theory. But Nature is not only quantum, but also relativistic. It is therefore worth asking, if relativistic effects only give rise to small corrections to the known results, or perhaps open new possibilities absent in the non-relativistic version of the information theory. In this talk we will review some of the most interesting results of the new and exciting field of relativistic quantum information.
2014-10-27 (Poniedziałek)
Zapraszamy do sali nr 1.40 (I piętro) przy ul. Pasteura 5 (nowy budynek Wydziału Fizyki UW) o godzinie 16:30  Calendar icon
prof. dr hab. Roman Stępniewski (Instytut Fizyki Doświadczalnej Wydziału Fizyki UW)

Nowe źródła światła – Nagroda Nobla z Fizyki w r. 2014

Streszczenie referatu:

W bieżącym roku Nagrodę Nobla z fizyki otrzymała trójka japońskich uczonych za „opracowanie efektywnych diod świecących niebieskim światłem”. W swoim referacie przedstawię fizyczne podstawy działania nowej klasy źródeł światła, jakie powstały dzięki ich pionierskim pracom. Omówię najważniejsze odkrycia w dziedzinie badań półprzewodnikowych struktur azotowych jakie doprowadziły do tego sukcesu. Wspomnę o polskim wkładzie w badania dotyczące tej tematyki, a także o wkładzie jednego z Noblistów w ten polski wkład.

Referat zostanie wygłoszony w ramach wspólnego posiedzenia konwersatoriów im. J. Pniewskiego i L. Infelda.

Zapraszamy!

Jacek Baranowski, Jan Kalinowski, Jerzy Kijowski, Czesław Radzewicz, Wojciech Satuła, Janusz Skalski

2014-10-09 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Professor Goetz A. Lehmann (Institute for Theoretical Physics I, Heinrich – Heine University Düsseldorf)

Plasma - based pulse amplification – a route to Exawatt Zettawatt laser pulses

In the last decade the increasing availability of Terra- and Petawatt class lasers with ps to fs pulse duration has intensified the interest in the relativistic interaction between laser radiation and matter. Today laser intensities of up to 1022 W/cm2 can be achieved routinely, delivering field strengths at which electrons become ultra-relativistic within a single cycle of the optical field. Via the interaction of such intense fields with plasma it is possible to generate electric and magnetic fields inside plasma of the order of TV/m and kilo-Tesla, respectively. This leads to several promising applications such as compact particle and radiation sources.
Laser pulses with power on the Exawatt/Zettawatt scale would not only improve current applications, but would open the door to access new regimes, e.g. direct access to the QED vacuum via the optical fields. Most high-intensity lasers today rely on the Chirped Pulse Amplification (CPA) scheme that can only hardly be scaled to these power levels due to material damage thresholds. A novel approach that allows circumventing these issues is the use of plasma as an amplification medium. Plasma oscillations (electron Langmuir waves or Ion oscillations) may be used as optical gratings, scattering the energy from a long pump pulse into a short seed pulse. Plasma-based pulse amplification is currently discussed as a prospective key component of the next generation high-intensity laser pulses.
The first part of the presentation introduces into the field of relativistic laser-plasma interaction and highlights the current research activities such as generation of GeV electron beams via wake-field acceleration, MeV proton acceleration from overdense plasma target interaction and generation of atto-second X-ray radiation.
In the second part of the presentation the theory of plasma-based laser-pulse amplification will be discussed. It will be shown that two types of amplifiers, Raman or Brillouin, are possible. The former uses electron plasma oscillations, the latter ion plasma oscillations to transfer energy from the pump pulse into the seed pulse. For both types, the present situation and future perspectives will be discussed.

2014-10-02 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 15:30  Calendar icon
Professor Matthias Neubert (Johannes Gutenberg-Universitaet Mainz)

Implications of the discovery of the Higgs boson

The discovery of a new kind of particle — the Higgs boson — at the CERNLarge Hadron Collider has marked the beginning of a new era in fundamental physics. Physicists are now eagerly exploring the properties of this mysterious new particle. The Higgs boson mediates a new kind of force, whose strength is proportional to the masses of the particles involved. It contains the key to understanding the mass of all elementary particles in the Universe, it offers new ways to search for physics beyond the Standard Model of particle physics, and it may have dramatic consequences for the fate of the Universe.
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