HIP NEWS September 29th 2014
Upcoming events in Finland: CERN´s 60th anniversary
See the link http://www.hip.fifi/?page_id=1963
DEPARTMENT OF PHYSICS / HIP JOINT COLLOQUIA / SEMINARS
Tuesday 30 September 2014 at 10.15 in A315
Shahin Sheikh-Jabbari (IPM, Tehran, Iran)
The Quest for Quantum Gravity, the necessity and viewpoints
Abstract: Gravity is the only interaction which appears among all existing objects and in our current physics is formulated through Einstein theory of General Relativity (GR). Although it has many theoretical appealing features and successes with the current experiments and observations, GR suffers from theoretical shortcomings. The most common way to remedy these shortcomings comes through quantization of the theory. Despite of many efforts and trying various approaches, a consistently quantized gravity has remained elusive. In this colloquium talk I will review these shortcomings and some of the main approaches taken to formulate Quantum Gravity.
Tuesday 30 September 2014 at 14.15 in A315
Tuomas Hapola (Durham)
Higgs Plus Multiple Jets with HEJ
Abstract: The High Energy Jets (HEJ) framework provides an approximation to the all-order perturbative calculation of observables in processes with multiple hard jets. In this talk I will first introduce the framework, and discuss recent comparisons to the data from the LHC and Tevatron. Then I will discuss predictions for the production of Higgs boson with multiple jets using HEJ.
Thursday 2 October 2014 at 10.15 in A315
Arttu Rajantie (Imperial College)
Quantum field theory of elementary magnetic monopoles
Abstract: Ever since Dirac’s discovery that quantum mechanics allows magnetic monopoles, there have been attempts to add them to quantum electrodynamics as dynamical degrees of freedom rather than as a static classical background as in Dirac’s calculation. However, the proposed formulations have been impractical due to issues like lack of manifest Lorentz invariance or locality. When ‘t Hooft and Polyakov discovered topological monopole solutions in GUT-like non-Abelian theories, the attention shifted to them. However, there is no physical reason to rule out the possibility of elementary monopoles, and some of their key properties can be different from ‘t Hooft-Polyakov monopoles. In particular, their mass is a free parameter and can therefore be light. I present a lattice formulation of QED with light elementary magnetic monopoles and show simulation results which demonstrate that they behave as expected. This shows that magnetic monopoles do not have to be related to grand unification, and that they can be light enough to be produced at the LHC and detected at the new MoEDAL experiment.
Wednesday 1 Oct 2014 at 14:15 in A315
Florian Niedermann (University of Munich)
The Universe as a Cosmic String
We are investigating modifications of general relativity which are operative at the largest observable scales. In that context we are investigating the model of brane induced gravity in 6D, a higher dimensional generalization of the DGP model. As opposed to different claims in the literature, we have proven the quantum stability of the theory on a linear level. In particular, we have shown that the Hamiltonian of the linear theory is bounded from below (Phys.Rev. D86 (2012) 124022). This result was a complete game changer: it opened a new window of opportunity for consistent modified Friedmann cosmologies.
Subsequently, it was shown that a brane with FRW symmetries necessarily acts as a source of cylindrically symmetric gravitational waves, so called Einstein-Rosen waves. Their existence essentially distinguishes this model from the DGP model and stimulated work on non-linear wave classification by virtue of the Weyl tensor (Phys.Rev. D88 (2013) 064047). (It was shown that its standard interpretation in terms of in-coming and out-going wave components fails for cylindrically symmetric geometries.)
In our most recent work we have numerically solved the full dynamical system of modified Einstein equations. As a result we have found two qualitatively different and dynamically separated classes of cosmologies: degravitating solutions for which the Hubble parameter settles to zero despite the presence of a non-vanishing energy density on the brane and super-accelerating solutions for which Hubble grows unbounded. The parameter space of both the stable and unstable regime was derived analytically and the observational relevance of both solutions could be inferred. (This will be published soon.)
Campus info sessions
on the new occupational health care agreement in November
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Networking – Strategic Theme of the Year:
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A. Golovnev 17.9. – 10.10. (MK)
L. Laperashvili 23.9. – 14.10. (AT)
F. Niedermann 1.10. – 3.10. (KE,SN)
S. Roy 1.10. – 31.10. (KH)