Konwersatorium im. Leopolda Infelda
2006/2007 | 2007/2008 | 2008/2009 | 2009/2010 | 2010/2011 | 2011/2012 | 2012/2013 | 2013/2014 | 2014/2015 | 2015/2016 | 2016/2017 | 2017/2018
Wielkość Marii Skłodowskiej-Curie
Stability of Matter-Antimatter Molecules
The study of matter-antimatter molecules has a long history, starting with the pioneering work of John A. Wheeler in 1946. Molecular states appears not only in atomic and molecular physics, but also in sub-atomic physics. We shall review the evidence for molecular states in subatomic systems and discuss the recently observed X(3872) as a heavy-quark meson molecule [1]. Because a large number of particles and antiparticles are produced in high-energy (e+)-(e-) annihilations and nuclear collisions, we examine further the stability of matter-antimatter molecules with constituents (m1+, m2-, m2bar+, m1bar-) under their mutual electromagnetic interactions [2]. We find that matter-antimatter molecules possess bound states if their constituent mass ratio m1/m2 is greater than about 4. This stability condition suggests that the binding of matter-antimatter molecules is a rather common phenomenon.
[1] Cheuk-Yin Wong, Phys. Rev. C69, 055202 (2004) [arXiv:hep-ph/0311088].
[2] Cheuk-Yin Wong and Teck-Ghee Lee, [arXiv:1103.5774] (2011).
Finding edge-states of graphene nanoribbons without any calculations
Exact results for the hydrogen plasma within path integral methods
The derivation of exact results for quantum Coulomb gases has to face several difficulties originating from screening and recombination of charges into atoms, ions and molecules. The path integral representation at finite temperature is the most suitable tool for a proper account of those phenomena in partially ionized gases. It leads to the introductionof an equivalent classical system made of loops with arbitrary shapesdistributed according to Wiener measure. The equilibrium quantities of thegenuine quantum gas are then formally represented by Mayer-likediagrammatical series for that system of loops. The path integraldescription in terms of loops allows us to perform systematic resummations of Coulomb chains which remove long range divergences, as well as reexponentiations which incorporate recombination at short distances. Such operations can be carried out within well-prescribed topological and combinatorial rules, thanks to the classical nature of Gibbs factors in the loop world. Mayer-like series are then exactly transformed into the so-called screened cluster representation, where graphs are now built with particle clusters and screened interactions.
Within the screened cluster representation, we derive exact expressions for both thermodynamics and correlations of a partially ionized hydrogen gas in the Saha regime, defined by a double zero-temperature and zero-density limit. Such expressions properly account for contributions of molecular or ionic species, without any adjustable parameters like in phenomenological approaches. Moreover, they shed light on the partial screening of van der Waals forces by free charges, and its relation with the algebraic nature of screening in quantum plasmas.
Ludwik Silberstein (1872-1948); życie i twórczość
Satellite Mission Planck: Description, Scientific Goals, and Early Results
Understanding the origin of ferromagnetism in semiconductors
To memory of Jan Gaj (1943-2011)
In course of the years, the origin of spontaneous magnetisation that has been observed in numerous semiconductors and oxides has arguably become one of the most controversial topics in the contemporary physics of condensed matter. After a general introduction to spintronics and magnetically doped semiconductors, I will argue [1] that surprising properties of these systems have two distinct roots (i) an intricate interplay between hole-mediated ferromagnetism and AndersonMott localisation and (ii) a highly non-random distribution of magnetic cations driven by a significant contribution of open d shells to the cohesive energy.
[1] see, T. Dietl, Nature Mat. 9, 965 (2010), and references therein.
Magnetic and color superfluid order in multiflavor Fermi gases
i) We investigate antiferromagnetic ordering of trapped spin-1/2 fermions using large-scale dynamical mean-field theory simulations. We find a clear experimental signature - enhanced double occupancy - for the onset of magnetic order at low temperatures in current experiments.
ii) We study the properties of three-flavor fermions in an optical lattice, where new exotic quantum states such as color superfluids arise in partial analogy to Quantum Chromodynamics. Low-temperature properties of this system are addressed using DMRG and dynamical mean-field theory. Wefind a strong interplay between magnetization and color superfluidity.
The size of the proton
The charge radius Rp of the proton has so far been known only with a surprisingly low precision of about 1% from both electron scattering and precision spectroscopy of hydrogen.
We have recently determined Rp by means of laser spectroscopy of the exotic "muonic hydrogen" atom. Here, the muon, which is the 200 times heavier cousin of the electron, orbits the proton with a 200 times smaller Bohr radius. This enhances the sensitivity to the proton's finite size tremendously.
Our new value Rp = 0.84184 (67) fm is ten times more precise than the generally accepted CODATA value, but it differs by 5 standard deviations from it. A lively discussion about possible solutions to the "proton size puzzle" has started.
Quantum entanglement: analysis and detection
Additional Sources for Physics Research Funding in the Future?
Axions as Dark Matter
Graphene future of nanoelectronics?
Graphene, a single layer of carbon atoms arranged in a honeycomb lattice, has attracted a lot of attention since its discovery in 2004. The material with the whole plethora of intriguing properties has been billed as wonder material that could one day determine the future nano-electronics, just replacing the silicon in processors. Actually, a 100 GHz field effect transistor based on graphene sheet has been announced recently.
In this lecture, we present a survey of the graphene properties that lead to intriguing physics (resembling relativistic physics) and make this material so promising candidate for future information technologies. We address the challenges of creating electronic devices built of graphene. We consider electronic structure of monolayer graphene flakes, multilayers of graphene obtained in epitaxial growth process, and recently obtained graphane (i.e., modification of graphene sheet covered with hydrogen atoms), which also is intensively studied.
Lepton pair creation in intense laser fields
Podstawy mechaniki kwantowej: prawdy, półprawdy, pytania
Współczesne teorie kwantowe zrodziły się w toku trudnych polemik i nawracających wątpliwości. Czy warto zachować je w pamięci? Mój mini-wykład będzie przeglądem niektórych pytań, na które odpowiedź znamy, innych, które pozostały otwarte, innych jeszcze, których wolimy nie zadawać.
- Dlaczego wierzymy w istnienie kwantów energii? Czy ich teoria musi być indeterministyczna?
- Czy funkcja falowa opisuje pojedyncza cząstkę? Czy redukcja pakietu falowego jest prawdą, czy fikcją?
- Czy ma miejsce zjawisko teleportacji w doświadczeniach typu Einstein-Podolsky-Rosen?
- Czy pojedynczy foton może wykryć bombę w odległości tysiąca km?
- Czy nasze drzewo wiadomości dobrego i złego jest obiektywne?