Events - Page 28
Carsten Lütken, UiO
The new states of matter and concomitant quantum critical phenomena revealed by the quantum Hall effect appear to be accompanied by an emergent modular symmetry. The extreme rigidity of this infinite symmetry makes it easy to falsify, but two decades of experiments have failed to do so, and the predicted location of quantum critical points is in accurate agreement with experiments.
The symmetry severely constrains the effective low energy physics of 1010 charges in two dirty dimensions. A toroidal σ‐model gives a critical exponent that is in close agreement with numerical simulations. A double scaling law uncovered in the data suggests that the wave‐function may be multi‐fractal.
The modular analysis can be extended to “relativistic” group IV materials like graphene, silicene, germanene and stanene, and where reliable data are available there appears to be agreement.
C.A. Lütken, Introduction to the role of modular symmetries in graphene and other 2-‐dimensional materials, Contemp. Phys. (2014), http://dx.doi.org/10.1080/00107514.2014.949445
C.A. Lütken, G.G. Ross, Quantum critical Hall exponents, Phys. Lett. A 378 (2014) 262–265, http://dx.doi.org/10.1016/j.physleta.2013.11.001
Pasquale Dario Serpico, LAPTh, Univ. de Savoy, CNRS
Despite its remarkable success, the Standard Model (SM) of particle physics does not address key facts revealed by cosmological and astrophysical observations. Until now, no signs of new physics have been discovered in laboratory experiments, leaving unclear what is the path chosen by Nature for the physics beyond the SM (BSM). I will discuss in this talk how indirect signals from Dark Matter (DM) might help us in this challenging "theoretical selection problem", with implications on foundational aspects of BSM physics. I will illustrate this point with possible DM interpretations of recent anomalies in multimessenger observations of energetic radiation of Galactic and extragalactic origin.
Jesús Zavala Franco, University of Copenhagen [slides]
Although there is substantial gravitational evidence for the existence of dark matter, its nature as a new particle beyond the Standard Model remains one of the biggest mysteries in modern astrophysics. The favourite theoretical model, Cold Dark Matter (CDM), assumes that non-gravitational dark matter interactions are irrelevant for galaxy formation and evolution.
Surprisingly, there is no strong evidence for the CDM hypothesis. Current astronomical observations allow significant departures that have a relevant impact on our understanding of how galaxies form and evolve. Moreover, the observed properties of the smallest galaxies have been consistently in conflict with the predictions of the CDM model.
In this talk, I will argue that to explain galaxy formation and evolution in the broadest sense, an effective dark matter theory must contain a wider range of dark matter particle physics without spoiling the success of CDM in reproducing the large-scale structure of the Universe, while addressing its outstanding challenges at the scales of individual galaxies.
Ivica Picek, Univ. of Zagreb
After the discovery of the Higgs boson, searching for the dark matter (DM) is one of the main targets for the LHC. In light of evidence for neutrino mass it would be appealing that DM particles account for a solution to the small neutrino mass. A radiative neutrino mass realization dubbed "scotogenic" (with DM particles in a loop) imposes an exactly conserved Z_2 symmetry to eliminate tree-level neutrino masses and to simultaneously stabilize a DM candidate.
In this talk I will discuss the possibility to avoid such ad hoc Z_2 symmetry: either by promoting it to a local gauge U(1)_D symmetry or by requiring that it arises "accidentally" (on account of the SM symmetry and a choice of the field content). In this context, I will discuss the testability of Majorana singlet, triplet and quintet DM candidates at the LHC.
Alejandro Ibarra, Technische Universität München [slides]
The search for the gamma-rays which are presumably produced in dark matter annihilations is hindered by the existence of large, and still poorly understood, astrophysical backgrounds. In this talk we will emphasize the importance of sharp spectral features for the identification of a dark matter signal. We will review the status of the search of the various spectral features that arise in Particle Physics scenarios and we will discuss the interplay with other search strategies.
Pat Scott , Imperial College London [slides]
Searches for particle physics beyond the Standard Model come in many forms, from searches for new particles at accelerators to gamma-ray and neutrino telescopes, cosmic ray detectors and ultra-clean experiments deep underground. Efforts to combine multiple search channels in 'global fits' to new physics scenarios typically consider only a subset of the available channels, and apply them to a very small range of possible theories. Astroparticle searches in particular are usually only included in a very approximate way, if at all. In this talk I will review recent progress in improving this situation, and preview some of the future developments and challenges in this field.
Michael Kachelriess, NTNU [slides]
The IceCube Collaboration announced 2012 evidence for the first detection of extraterrestrial neutrinos. Meanwhile, the discovery of a extraterrestrial neutrino flux (of surprisingly large magnitude) has been established. After a review of the basic ideas of high-energy neutrino astrophysics, I discuss possible sources for these neutrinos and their signatures. I discuss the neutrino yield from collisions of cosmic ray nuclei with gas and the possibility that Galactic sources can explain the IceCube excess. I review also the cascade bound on extragalactic neutrinos and its consequences.
Jörn Kersten, Universitetet i Bergen [slides]
Despite the astonishing success of the standard LambdaCDM cosmological scenario, there is mounting evidence for a tension with observations. For example, some measurements indicate that a part of the dark matter is hot. In addition, the observed properties of relatively small galaxies do not quite agree with the predictions by simulations of structure formation.
I will discuss a simple particle physics model containing cold dark matter (DM) and sterile neutrinos. Both are charged under a new gauge interaction. The resulting DM self-interactions and DM-neutrino interactions resolve the problems with structure formation. The sterile neutrinos can account for both a small hot DM component and the neutrino anomalies found in short-baseline experiments.
Anders Kvellestad, UiO
Recently a few small (but intriguing) deviations from Standard Model predictions have been identified in the LHC data, one being an excess in the dilepton spectrum in a CMS search for so-called 'kinematic edges' -- a classic signal of physics models with heavy particles decaying through sequential two-body decays. We present an interpretation of this excess in terms of a supersymmetric model with squarks undergoing such sequential decays down to the lightest neutralino, which is a viable candidate for particle dark matter. The good-fit parameter space of the model is presented, along with predictions for squark production at the upcoming 13 TeV LHC run.
Further, using the above analysis as an example, we briefly comment on the main challenges of confronting complex models like Supersymmetry with experimental results, and present an ongoing effort to overcome some of these challenges.
Marius L. Meyer, UiO
In recent years there has been extensive interest in the study of strongly correlated states of cold atoms motivated by analogies with exotic states known from low-dimensional electronic systems, particularly quantum Hall states. In this talk I will present an analysis of the yrast states of two-component rotating Bose gases using Jain's composite fermion (CF) approach. A particularly simple subset of CF states are found to give very good approximations to the lowest energy states for low angular momenta.
-A new window on our Space environment: The polarization of the auroral emissions. A French – Norwegian discovery.
Kjetil Børkje, UiO
Over the past few decades, tremendous experimental progress has been made to engineer and control artificial quantum systems. The motivation for this type of research will be discussed, both from a fundamental and a technological point of view. Some of the most important recent developments will be presented, with focus on two areas specifically: a) the quest to realize quantum information processing and b) the effort to bring large-scale mechanical systems into the quantum regime. A few examples from my own theoretical contributions to the field of cavity optomechanics will be discussed. Finally, I will try to identify some new challenges going forward.Øystein Elgarøy, UiO
On March 17th this year the team behind the BICEP2 experiment announced the discovery of so-called B-mode polarization in the cosmic microwave background radiation at large angular scales. There is some tension between their claim and the results from the Planck satellitte, but I will assume that it is correct and try to explain why it is important. What is the link between B-mode polarization and the physics of the very early Universe?
Fabiola Gianotti is a new honorary doctor at the University of Oslo. This is her acceptance speech.
The event is free and open to all, no registration necessary.
The 3nd International Conference on New Frontiers in Physics (ICNFP2014) will be held 28.07-06.08.2014 in OAC, Kolymbari, Crete.
Lars Andreas Dal, UiO
The nature of Dark Matter is one of the large open questions in physics today. Observations indicate that Dark Matter likely consists of an unknown species of particles, which allows for the possibility of indirectly detecting Dark Matter by searching for the decay/annihilation products from these particles in cosmic rays.
With its very low expected astrophysical background, the antideuteron channel is particularly well suited for such searches. I will here discuss the challenges in correctly calculating the expected cosmic ray antideuteron flux, with focus on the uncertainty from hadronization models employed in Monte Carlo event generators.
Jan Olav Eeg, UiO
Recent measurements for direct CP-violation in decays of neutral charmed mesons (explicitly D0-> K+ + K- and/or D0 -> π+ + π- ) might indicate the existence of New Physics beyond the Standard Model. A concrete model to explain the effect is proposed by Altmannshofer et al. This model, based on a colored flavor changing scalar, will also generate a new contribution to the electric dipole moment of the neutron (NEDM). I present a calculation for this quantity within the proposed New Physics model. The calculation shows that the obtained value for the NEDM within the model is close to its experimental bound.
Olav Syljuåsen, UiO
Quantum mechanics predicts that a particle in a periodic potential will oscillate when a constant force acts on it. The oscillation pattern is rather unusual from a classical point of view as it is the external force which determines its frequency and amplitude. Such Bloch oscillations were for a long time controversial, and it took about sixty years until they were finally observed in semiconductor superlattices. In this talk I will discuss the possibility of observing Bloch oscillations in magnetic materials. In particular I will focus on neutron signatures of Bloch oscillations in one-dimensional anisotropic ferromagnets.
Liliana Velasco-Sevilla, Universität Hamburg
The Standard Model (SM) has successfully described most part of the interactions of elementary particles, however it has many free parameters, most of them related to the masses and the mixing of its fermions. The Higgs mechanism explains the existence the SM fermion masses, but it does not explain the mass spectrum, the mixing pattern and the number of generations of matter. These three last issues are collectively known as the flavour problem and the Charge-Parity (CP) violation is known as the CP problem.
Flavour and CP observables constrain severely extensions of the SM. However, this is a chance to test mechanisms that could solve flavour and CP issues and which may be only realizable in supersymmetry or other extensions of the SM. Then, I will review recent flavour and CP observations. In the third part, I will talk about the possibilities to solve these problems in supersymmetry. Finally, I will mention perspectives to identify signatures of the supersymmetric flavour violating parameters from experiments at the LHC.
Bryan Zaldivar, Université Libre de Bruxelles
This talk is about mechanisms to generate the observed Dark Matter abundance, which has not been in thermal equilibrium with the radiation plasma in the early universe. They are complementary to the standard "WIMP" paradigm. Special focus on the inflationary reheating period is given. Finally, some thoughts about possible implications of primordial gravitational waves's measurements on Dark Matter are presented.
Parampreet Singh Walia, UiO
The cosmological predictions of the angular power spectrum and structure formation are dependent on the chosen initial conditions of perturbations at early radiation dominated epoch. I will start by introducing the general mathematically possible initial conditions for scalar perturbations. Single field inflationary models produce Adiabatic initial conditions and the current CMB data strongly supports adiabatic initial conditions. With multi-field inflationary models one can produce isocurvature perturbations. A signal for isocurvature perturbations is of high importance for particle physicists as they predict the existence of exotic particles like axions and curvatons. I would present my work on trying to find an evidence for a (possibly) correlated adiabatic and isocurvature mode. The CMB datasets used for constraining models are WMAP9, QUaD and ACBAR. In the end, I would discuss the current status of isocurvature perturbations after PLANCK.
Christoph Weniger, University of Amsterdam
One of the major challenges of astroparticle research is to uncover the particle nature of dark matter. Weakly interacting massive particles (WIMPs) are the most popular candidates and currently scrutinized by a large number of experiments. In particular indirect searches for the self-annihilation products of WIMPs in the gamma- and cosmic-ray sky are a promising avenue to follow. I will discuss different techniques that aim at an identification of a dark matter contribution over the astrophysical background, recent claims for dark matter signals in the Fermi LAT data, and challenges for future experiments.