Calendar of Physics Talks Vienna

Beta-decay total absorption spectroscopy for basic and applied research
Speaker:Prof. Dr. Jose TAIN (Instituto de Fisica Corpuscular, Univ. Valencia and C.S.I.C. Edificio de Institutos de Paterna, Valencia, Spain)
Abstract:An accurate determination of the beta-decay intensity distribution is important for basic nuclear physics but also in other fields as astrophysics, reactor technology and neutrino physics. Total absorption spectroscopy is the only way to obtain accurate information about the beta intensity distribution for complex decays. Examples of the information that can be obtained about the structure of atomic nuclei and of the application of these data to other fields will be shown. The plans for future work at existing or planned radioactive beam facilities will be highlighted.
Date: Mon, 26.01.2009
Time: 16:00
Duration: 60 min
Location:Sem. 134A, Freihaus, Turm B, 5. OG

Making an optical clock with magnesium
Speaker:Prof. Ernst M. Rasel (Leibniz Universität Hannover)
Abstract:In this paper we report on our work directed towards a lattice clock [1] based on magnesium. In the case of the bosonic isotope 24Mg, the ac-Stark shift induced by the optical lattice vanishes for the transition 1S0 &-->8594; 3P0 around 432 nm. [2] The linewidth of the strongly forbidden clock transition can be tailored with an external magnetic field [3]. According to [4] this clock would display the lowest black-body radiation shift of all alkaline- earth metals, which is e.g. 10 times smaller than in Sr. The paper presents the first absolute frequency measurement of the 1S0 & -->8594; 3P1 intercombination line in 24Mg [5] based on thermal beam and cold atom interferometry. In combination with previous measurements, the results permit to determine other transitions in the 1S0 & -->8594; 3PJ system including the strictly forbidden 1S0 → 3P0 transition. In order to prepare atoms for the frequency measurements, we use laser cooling of the metastable state 3P2 via the transition 3P2& -->8594; 3D3, which permits to employ sub-Dopplerlaser cooling techniques. Atoms in this state are now routinely produced in our laboratory by operating synchronously two magneto-optical traps trapping atoms in the ground and metastable atoms respectively [6]. We showed that atoms in the ground state can be transferred in the long-lived metastable state with high efficiency by using the intercombination transition 1S0 &-->8594; 3P1. The frequency measurements using cold atoms are performed with a transportable caesium clock and via a telecom fibre link with an optical clock, both provided by the PTB. For this purpose, a frequency transfer with a telecon laser was established via a public fibre link between Hanover and Braunschweig. [1] M. Takamoto, F.-L. Hong, R. Higashi1 and H. Katori, Nature 435, 321-324 (2005) [2] V. D. Ovsiannikov, V. G. Palchikov, A. V. Taichenachev, V. I. Yudin, H. Katori, and M. Takamoto, Phys. Rev. A 75, 020501(R) (2007). [3] A. V. Taichenachev, V. I. Yudin, C. W. Oates, C. W. Hoyt, Z. W. Barber, and L. Hollberg, Phys. Rev. Lett. 96, 083001 (2006). [4] S. G. Porsev and A. Derevianko, Phys. Rev. A 74, 020502(R) (2006).[5] J. Friebe, A. Pape, M. Riedmann, K. Moldenhauer, T.E.Mehlstäubler, N. Rehbein, C. Lisdat, E.M. Rasel, and W. Ertmer subm. to Phys. Rev A [6] J. Friebe, A. Voskrebenzev, A. Pape, M. Riedmann, K. Moldenhauer, E.M. Rasel, and W. Ertmer, in preparation
Date: Mon, 26.01.2009
Time: 17:30
Duration: 60 min
Location:TU Wien, Neues EI8, Pötzl Hörsaal, Stiege 1, EG, Gußhausstraße 27-29, 1040 Wien
Contact:Prof. Markus Arndt, Universität Wien, Fakultät für Physik, Quantum Optics, Quantum Nanophysics & Quantum Information

Vienna Theory Lunch Club - F-theory: Introduction and recent developments
Speaker:Andres Collinucci (TU Wien)
Abstract:Fourteen years ago, string theory underwent a major paradigm shift when techniques were developed to study the theory non- perturbatively, i.e. in its strongly coupled regime. More specifically, the introduction of D-branes and eventually M-theory opened up windows that relate the different versions of string theory, in different corners of its parameter space. A year after the idea of M-theory was conceived, Vafa developed what can be thought of as its obscure partner, known as "F-theory". Although it is less understood conceptually, F-theory is a more practical tool for model building, i.e. for trying to make contact with the standard model. Curiously, the year 2008 has seen a revival of "F-theory", as new results have emerged in the direction of model building.
In this talk, I will give an overall rough picture of M-theory and F- theory without assuming prior knowledge of string theory. Then, as time permits, I will show an explicit F-theory toy model. Finally, I will summarize the most recent developments in this branch.
Overview Lunch Club
Date: Tue, 27.01.2009
Time: 12:30
Duration: 60 min
Location:University of Vienna, Boltzmanngasse 5, 5th Floor, Large Seminar Room
Contact:Max Attems, Daniel Grumiller, Beatrix Hiesmayr

Qu-transitions: probing the critical zero point fluctuations of matter with heavy electron materials
Speaker:Piers Coleman (Center for Materials Theory, Rutgers University)
Abstract:This seminar will describe the playground for new insights into the nature of "qu-transitions"-quantum phase transitions provided by heavy fermion physics. Last century, physicists were profoundly shaken by the discovery of universal power-law correlations at thermal second-order phase transitions. Today, our understanding of phase transitions enters the quantum era with the discovery of quantum phase transitions: phase transitions at absolute zero driven by the violent jigglings of quantum zero-point motion squeezed out to macroscopic dimensions. These transitions occur in a wide range of materials, including ferromagnets, helium-3, ferro-electrics, heavy electron and high temperature superconductors, and they profoundly alter the properties of a material. While a distant cousin of classical criticality, quantum criticality is closer in spirit to the Casimir effect of the electromagnetic vacuum, the extra fermionic dimension of metals converts this into a major unsolved physics problem. I'll talk about, and add my perspective on the some of the key questions, illustrating them with experimental data. In particular: Does the electron break up at quantum critical point ? Can quantum critical points become qu-phases? and of course - Is quantum criticality the breading ground for high temperature superconductivity?
Date: Wed, 28.01.2009
Time: 16:30
Location:Technische Universität Wien, Seminarraum 138B, 7. OG, Turm C (rot), Wiedner Hauptstraße 8-10, 1040 Wien
Contact:S. Bühler-Paschen

On the geometry of the truncated Heisenberg algebra
Speaker:Maja Buric (Belgrad Univ.) (Fakultät für Physik)
Abstract:im Rahmen des Seminars für Mathematische Physik
Date: Thu, 29.01.2009
Time: 16:15
Duration: 60 min
Location:Großer Seminarraum, Boltzmanngasse 5, 5. Stock
Contact:H. Grosse