|
Calendar of Physics Talks Vienna
| Tensionless strings : A perspective from the worldsheet |
| Speaker: | Pulastya Parekh (Indian Institute of Technology Kanpur, India) |
| Abstract: | I will be speaking about the construction of the tensionless limit of closed bosonic string theory in the covariant formulation in the light of Galilean conformal symmetry that rises as the residual gauge symmetry on the tensionless worldsheet.I will show how the analysis of the fundamental tensionless theory is related to the tensionless limit that is viewed as a contraction of worldsheet coordinates.The connection to massless higher spin states can be seen naively.This analysis can be extended to the closed superstring to obtain the Super Gallilean Conformal Algebra (SGCA),that can be realised in two distinct ways:the Homogenous and the Inhomogenous SGCA.I will also comment on the hermiticity properties of fermions in case of the Inhomogeneous tensionless superstring.We will see that the analysis of the quantum regime uncovers interesting physics.The degrees of freedom that appear ... |
| Date: | Tue, 29.01.2019 |
| Time: | 13:45 |
| Duration: | 60 min |
| Location: | Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock |
| Contact: | S. Fredenhagen, D. Grumiller |
| QCD correlators at higher orders |
| Speaker: | Matthias Jamin (ICREA Research Institut de Fisica d'Altes Energies (IFAE) Edifici Cn, Universitat Autonoma de Barcelona) |
| Abstract: | Estimating uncertainties for perturbative predictions in QCD often hinges on
our knowledge of higher-order corrections. Different approaches are available
to achieve this goal like the study of scale and scheme variations, as well as
investigating the general renormalon structure. Those approaches are exemplified
for the case of QCD two-point correlation functions. In order to study scheme variations,
it proves useful to introduce a particular scheme, the so-called C-scheme, in which the
QCD beta-function is manifestly scheme invariant and known to all orders. On the other
hand, the renormalon structure of QCD correlators can provide important insight into
the general behaviour of their perturbative series. This general behaviour also suggests
the existence of a scheme-invariant coupling in full QCD which will be introduced and its
implications discussed.
|
| Date: | Tue, 29.01.2019 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock |
| Contact: | A. Hoang, S. Plätzer, M. Procura |
| High resolution tracking with scintillating fibres - The LHCb SciFi Tracker |
| Speaker: | Dr. Lukas Gruber (CERN) |
| Abstract: | The use of plastic scintillating fibres (SciFi) as active elements in particle detectors has a long tradition. In recent years, the development of high performance SiPM detector arrays revived the interest in the SciFi technology. Combining the two technologies allows to build intrinsically fast, low mass high resolution tracking detectors with great geometrical flexibility. As a recent example, the LHCb SciFi tracker is going to replace the current outer and inner trackers, consisting of straw tubes and silicon micro strip detectors, respectively, by using a single detector technology – 11,000 km of scintillating fibres with 250 µm diameter, enabling a spatial resolution of better than 100 µm for charged particles.
The LHCb tracker requirements and environment...
[full abstract available at: https://indico.smi.oeaw.ac.at/event/301/] |
| Date: | Wed, 30.01.2019 |
| Time: | 17:00 |
| Duration: | 60 min |
| Location: | Stefan-Meyer-Institut, Boltzmanngasse 3, 1090 Wien, Seminarraum 3-2-08 (2. Stock) |
| Contact: | Prof. Dr. Eberhard Widmann, Dr. Martin Simon |
| Attractors of the Einstein-Klein-Gordon system |
| Speaker: | Zoe Wyatt (Edinburgh and Vienna) |
| Abstract: | The Milne cosmological model, a specific case of the FLRW family of cosmologies, represents an expanding universe emanating from a big bang singularity with a linear scale factor. With such a slow expansion rate, particularly compared to related isotropically expanding models (such as de Sitter), there are interesting questions one can ask about stability of this spacetime. For example previous results have shown that, when looking at the initial value problem, the Milne model is a stable solution to the vacuum Einstein, Einstein-Klein-Gordon and Einstein-Vlasov systems. Motivated by the last result, I will discuss our proof of the stability of the Milne model to the Einstein-Klein-Gordon system. This was shown recently by J. Wang using an alternative gauge and method. Thus I will also give comparisons between our method and results. This is joint work with D. Fajman. |
| Date: | Thu, 31.01.2019 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Arbeitsgruppe Gravitation, Währinger Strasse 17, Seminarraum A, 2. Stock, 1090 Wien |
| Contact: | P.T. Chrusciel, D. Fajman |
| Classical de Sitter Solutions of 10d Supergravity |
| Speaker: | Alessandro Tomasiello (University Milano-Bicocca) |
| Abstract: | Finding de Sitter compactifications of string theory has long been a challenge. They are known to require quantum corrections, or orientifold planes, or both. Most existing models rely on effective four-dimensional actions, or work with the ten-dimensional action but involve 'smearing' the internal O-planes. After a brief review of such efforts, we present some new numerical solutions with localized and back-reacted O8-planes. While the solution is singular and strongly-coupled near one of the O8s, it exhibits the same behavior observed for such objects in flat space and in a variety of AdS solutions in various dimensions, with solid holographic cross-checks. Away from the O8s the solution can be made parametrically weakly-coupled thanks to some moduli, whose nature might however be changed by string theory corrections. |
| Date: | Thu, 31.01.2019 |
| Time: | 16:00 |
| Duration: | 60 min |
| Location: | Sem.R. DB gelb 10 - Freihaus, TU Wien |
| Contact: | Timm Wrase |
| Cosmological Constant Problem: Deflation During Inflation |
| Speaker: | Benjamin Koch (U. Catol. Chile, Santiago) |
| Abstract: | We argue that the discrepancy between the Planck mass scale and the observed value of the cosmological constant can be largely attenuated, if those quantities are understood as a result of effective, and thus scale dependent, couplings. We exemplify this mechanism for the early inflationary epoch of the universe by solving the corresponding effective gap equations, subject to an energy condition. Several non-trivial checks and extensions are discussed. A comparison of our results to the renormalization group flow, obtained within the asymptotic safety program reveals a stunning agreement. |
| Date: | Fri, 01.02.2019 |
| Time: | 16:00 |
| Duration: | 60 min |
| Location: | Institute for Theoretical Physics, TU Wien, Seminar room 10th floor (yellow area), Wiedner Haupstr. 8-10, 1040 |
| Contact: | Anton Rebhan |
|