Events - Page 14

Time and place: Jan. 19, 2017 1:15 PM, Lille Auditorium (Ø157)

Master of Science Jørgen Høgberget at Department of Physics will be defending the thesis Microscopic Modeling of Confined Crystal Surfaces: Growth, dissolution, and equilibrium for the degree of the Degree of Philosophiae Doctor

Time and place: Jan. 19, 2017 10:15 AM4:00 PM, Lille Auditorium (Ø157)

Trial lecture: Pattern formation in granular materials (10:15)

Dissertation: Microscopic Modeling of Confined Crystal Surfaces: Growth, dissolution, and equilibrium (13:15)

Time and place: Jan. 19, 2017 10:15 AM, Lille Auditorium (Ø157)

Doctoral candidate Master of Science Jørgen Høgberget at Department of Physics will give a trial lecture on the given topic: "Numerical investigations of percolation problems"

Time and place: Jan. 18, 2017 1:05 PM2:00 PM, Ø467

Farinaldo Queiroz, MPI Heidelberg

We review the  searches for dark matter namely, direct, indirect and collider, emphasizing the importance of complementary strategies and discuss how one can eventually unveil the nature of dark matter.

(The slides will be available here)

Time and place: Jan. 11, 2017 1:05 PM2:00 PM, Ø467

Alessandro Cuoco, RWTH Aachen

I will discuss the implication for dark matter (DM) indirect searches of the recent precise measurements of cosmic-ray (CR) antiprotons from AMS-02. With respect to previous works we use a new updated CR propagation model consistent with the AMS-02 data. Furthermore, we fit at the same time, in a self-consistent way, both DM and the propagation parameters. We find a significant (4.5 sigma) indication of a DM signal for DM masses near 80 GeV, which, interestingly, is also compatible with the similar excess present in the Galactic center  in  gamma rays. Possible systematic effects will be also discussed. In terms of DM exclusion limits, we find stringent constraints a factor of 4-5 stronger than limits from gamma-ray observations of dwarf galaxies.

(The slides will be available here)

Time and place: Dec. 16, 2016 3:15 PM, Seminar Room FV414

The last Poster Seminar of 2016! Please all come, drink wine and discuss science.

Time and place: Dec. 2, 2016 1:15 PM3:45 PM, PGP seminar room (FV 414)

On December 2nd, a short EarthFlows seminar will take place at PGP.

Time and place: Dec. 1, 2016 12:30 PM1:15 PM, Store fys aud

Speaker: Vadim Makarov. Institute for Quantum Computing, University of Waterloo, Canada.

Time and place: Nov. 30, 2016 1:05 PM2:00 PM, Ø467

Julia Harz, UPMC Paris

To achieve a more precise prediction of the supersymmetric dark matter relic density, we have calculated next-to-leading order SUSY-QCD corrections to neutralino (co)annihilation processes including Coulomb enhancement effects. We demonstrate that these corrections can have significant impact on the prediction of the dark matter relic abundance and are thus of general interest for parameter studies. For particle physics observables at colliders, it has been common practice for many decades to estimate the theoretical uncertainty by studying the variation of the predicted cross sections with a priori unpredictable scales. In astroparticle physics, this has so far not been possible, since most of the observables were calculated at Born level only, so that the renormalization scheme and scale dependence could not be studied in a meaningful way. We will present the first quantitative study of the theoretical uncertainty of the neutralino dark matter relic density from scheme and scale variations.

(The slides will be available here)

Time and place: Nov. 25, 2016 3:15 PM, Seminar Room FV414

by Unni Vik from CEES/EvoGene, Department of Biosciences, University of Oslo.

Time and place: Nov. 23, 2016 1:05 PM2:00 PM, Ø467

Marit Sandstad, NORDITA Stockholm

The idea that black holes of a wide range of masses could form from highly overdense regions in the very early universe has been around since the early seventies, when it prompted Steven Hawking to derive the theory of Hawking radiation. Since then, no primordial black holes have been seen, but as more accurate observations of the universe and our surrounding galaxies have been made they have been suggested as possible culprits for unexplained cosmic rays, the supermassive black holes in the centres of galaxies or the entirety of dark matter. However, as the unexplained cosmic rays turned out to be non-detections, so far all we have got at present are constraints on their abundance from various observations across nearly all possible scales. However, having only constraints might not be entirely a disadvantage. If the mechanisms proposed for the formation of primordial black holes is correct, their non-existence implies that the primordial power spectrum from inflation cannot have been too large. This is very interesting as... [abstract continued below]

(The slides will be available here)

Time and place: Nov. 10, 2016 12:00 PM1:00 PM, Store fys aud, The Physics Building
Thors Hans Hansson, Stockholm University and NORDITA
Time and place: Nov. 2, 2016 1:05 PM, Ø467

Jeriek Van den Abeele, FI

Given that physical problems rarely have exact solutions, the importance of perturbation theory can hardly be overstated. Yet often, a closer look reveals that it is divergent and ill-defined! Non-perturbative effects, ubiquitous in nature and quantum theories, have to be accounted for explicitly in attempts to make sense of perturbation theory. The perspective of the resurgence framework leads to new ways of understanding perturbative expansions and reveals surprising connections to non-perturbative physics. In this talk, I will illustrate how resurgence manifests itself in the quantum mechanical context of a cosine potential, emphasising the importance of quantum tunnelling for its energy spectrum and highlighting how non-perturbative contributions are intricately encoded in perturbation theory.

(The slides will be available here)

Time: Oct. 28, 2016 3:15 PM

by Åge Gellein Larsen from SINTEF. 

Time and place: Oct. 26, 2016 1:05 PM2:00 PM, FØ467

Tommaso Dorigo, INFN Padua

The CDF collaboration led for two decades the investigation of the high-energy frontier in the search for new physics at the highest energies until then achieved, provided by the Tevatron collider. In a recently published book the author describes how the experiment handled several unexplained phenomena found in the data, and the complex sociology of a large collaboration divided by different feelings on how to deal with those unexpected findings. The seminar will start by discussing the history of those anomalies and their resolution, and then focus on the statistical problem of defining a proper discovery level for new phenomena and on the non-trivial issues it entails.

Time and place: Oct. 19, 2016 1:05 PM2:00 PM, Ø467

Sebastian Wild, DESY Hamburg

One of the most promising strategies to probe WIMP dark matter is direct detection, i.e. the search for nuclear recoils produced by the elastic scattering of dark matter particles. After giving a general introduction to the theoretical framework and experimental status of direct detection, I will present recent developments which allow to interpret the experimental data without the need to specify the (unknown) velocity distribution of dark matter, called "halo-independent methods". Specifically, I will discuss to what extent future experiments can pinpoint the particle physics properties of dark matter in a halo-independent way. I will also present a novel approach to derive upper limits on the scattering cross section of dark matter using already existing experiments, again without the need to specify the velocity distribution.

(The slides will be available here)

Time: Oct. 14, 2016 3:15 PM

by Wenlu Zhu, a visiting Associate Professor from the University of Maryland.

Time and place: Sep. 30, 2016 3:15 PM, Seminar Room FV414

by Wojciech Jacek Miloch (Associate Professor, Department of Physics, UiO).

Time and place: Sep. 29, 2016 1:05 PM, Ø467

Anastasia Sokolenko, FI

In this work we propose a new interesting channel for searching new physics at the LHC. This channel is connected to the diphoton channel via electroweak gauge symmetry of the Standard Model (SM). We discuss the possibility that an apparent diphoton signal is in fact produced by the 4-photon channel, where a pair of collimated photons is misidentified as 1 photon due to finite angular resolution of the detector. In this case we expect that the gauge symmetry of the SM connects the diphoton channel to three boson channels. Also we notice that the same mechanism could give an experimental signature of $Z\rightarrow \gamma\gamma$ decay, which is theoretically forbidden by the Landau-Yang theorem. For definiteness we illustrate these ideas using one of the models that was discussed to explain the recent 750 GeV resonance, even if the later signal was not confirmed.

(The slides will be available here)

Time and place: Sep. 28, 2016 1:05 PM, Ø467

Jens Paaske, NBI Copenhagen

Motivated by recent experiments, we study lattices of magnetic adatoms exchange coupled to the surface of a conventional s-wave superconductor. We show that a variety of collective magnetic and electronic phases emerge in this system, due to the interplay between ferromagnetism and superconductivity. In particular, an adatom chain on a bulk (2d or 3d) superconductor can order into a magnetic spiral state leading to, and stabilized by, the opening of a topological superconducting gap within the band of YSR states induced by the adatoms. The spiral wave-vector increases sharply as the YSR energy is lowered from the quasiparticle continuum, due to a strong spin-spin exchange interaction mediated through the band of sub-gap YSR states. As the YSR band enters the topological phase, the wave-vector exhibits a peak and is thereafter driven down towards ferromagnetism due to YSR state double-exchange. We provide the range of YSR energies and adatom spacing where these phases exist for adatoms on a 3d, or 2d  superconductor. The magnetic ordering within a 2d YSR lattice is also explored.

(The slides will be available here)

Time and place: Sep. 22, 2016 5:30 PM7:00 PM, DNVA, Drammensveien 78

Professor Eric Priest, St Andrews University, Scotland:

Our Dynamic Sun

Time and place: Sep. 21, 2016 1:05 PM2:00 PM, Ø467

Oleg Lebedev, University of Helsinki

I will discuss a special role of the Higgs boson in probing the hidden sector and its connection to dark matter and inflation.

(The slides will be available here)

Time and place: Sep. 15, 2016 10:15 AM11:15 AM, Lille aud øst

Alfredo Galindo-Uribarri, Oak Ridge National Laboratory / University of Tennessee, Knoxville.

Time and place: Sep. 2, 2016 3:15 PM, Seminar Room FV414

by Octavio Palma

Time and place: Aug. 31, 2016 1:05 PM2:00 PM, Ø467

Andi Hektor, NICPB Tallinn

I will give a short introduction to Dark Matter physics. I will sum up the the main evidences of Dark Matter from the Galactic to large cosmological scales. So far the evidences are only gravitational. I will point out that even the gravitational signals of Dark Matter can hint about the deeper nature of Dark Matter, especially having soon new data from the Gaia and other soon starting experiments. Beyond gravitation, we have many experimental constraints on the ‘particle’ nature of Dark Matter and only few questionable hints of Dark Matter. Those experiments involve the accelerator (LHC at CERN), underground (‘direct detection') and cosmic experiments (‘indirect detection’). Due to rapidly evolving experimental and observational bounds the mainstream candidate of Dark Matter, Weakly Interacting Massive Particle, is losing its ground. I will point out some interesting escape scenarios of WIMP. I will conclude highlighting some interesting alternatives for WIMPy Dark Matter.

(Slides will be available here)