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Time and place: June 24, 2015 1:05 PM, Ø467

Kalliopi Petraki, NIKEF Amsterdam [slides]

Observations of the galactic and sub-galactic structure of our universe suggest that a shift from the collisionless cold dark matter paradigm may be needed. Dark matter with sizable self-interactions offers a compelling explanation of these observations.

Particle​ ​physics models of self-interacting dark matter can be well accommodated within the asymmetric dark matter scenario. Asymmetric dark matter hypothesizes that the relic dark​ ​matter abundance is due to an excess of dark particles over antiparticles, and allows for sizable and direct couplings of dark matter to light force mediators.

In addition, the dark particle-antiparticle asymmetry may be related to the baryon asymmetry of the universe, thus offering a dynamical explanation for the similarity of the dark and the ordinary matter abundances. Exploring the low-energy phenomenology of self-interacting asymmetric dark matter, including the effect on the dynamics of dark matter halos and possible detection strategies, presupposes understanding the cosmology of these models, which can be quite involved. I will discuss the above, and illustrate them in the context of the atomic dark matter model.

Time and place: June 3, 2015 1:05 PM, Ø467

Kai Schmidt Hoberg, DESY, Hamburg [slides]

I will review motivations for the existence of self interacting dark matter and discuss possible astrophysical observables. Self-interactions of dark matter particles can potentially lead to an observable separation between the dark matter halo and the stars of a galaxy moving through a region of large dark matter density. Such a separation has recently been observed in a galaxy falling into the core of the galaxy cluster Abell 3827. I discuss the DM self-interaction cross section needed to reproduce the observed effects.

Time and place: May 27, 2015 1:05 PM, Ø467

Thomas Jacques, Université de Genève, Switzerland [slides]

As beyond-standard-model physics continues to elude discovery at the LHC, it becomes increasingly important to ask what we can learn about dark matter in a model-independent way. I will introduce the theory and usage of effective operators; these have become popular in recent years as a way to construct model-independent constraints on dark matter, but at LHC energies it is crucial to understand their significance and limitations, and how they can be used to compare the reach of vastly different experiments. With this in mind, I will also discuss the next step beyond effective operators, and techniques to link the search for missing energy with the much-sought-after Dark Matter.

Time and place: May 13, 2015 1:05 PM, Ø467

Mark Burgess

Physics is probably the most successful science when it comes to describing how things behave, but it avoids interpreting the meaning or the intent of behaviours. In technology, especially IT, meaning and intent are at the top of the list when it comes to description, but IT fails to describe system dynamics convincingly. Promise Theory is an attempt to unify dynamical and semantic descriptions of systems, inspired by the successes of physics - and it sheds an interesting light on both fundamental physics and information science.

Time and place: Apr. 29, 2015 1:05 PM, Ø467

Thomas Schwetz-Mangold, Stockholms Universitet [slides]

The observation of neutrino oscillations requires that neutrinos have a tiny but non-zero mass. This implies that the Standard Model of particle physics has to be extended in some way beyond its original formulation where neutrinos are massless. We review the present status of neutrino oscillations and give a brief outlook on future developments in the field. We speculate on the implications for physics beyond the Standard Model and discuss the challenges to identify the mechanism responsible for neutrino mass.

Time and place: Apr. 24, 2015 2:15 PM, Ø467

Nils-Erik Bomark, University of Warsaw

Within the MSSM, the heavy stops required to meet the experimental value of the Higgs mass, poses tension with naturalness, the main reason to believe in supersymmetry at LHC scales. This is alleviated in the NMSSM, where especially the possibility of a light singlet-like scalar can easily push the Higgs mass up to the measure value.

The presence of a singlet-like scalar and pseudoscalar gives rise to LHC phenomenology potentially rather different from the MSSM as these particles can be very light without coming in conflict with observations. In this presentation I will discuss the discovery prospects of these light pseudoscalars in the NMSSM. As direct production of such singlet-dominated particles is very difficult, the main focus will be on channels where heavier scalars decay to pairs of pseudoscalars or pseusodscalars and Z bosons. I will demonstrate that the LHC should be capable of probing a large part of the NMSSM parameter space through these channels.

Time and place: Apr. 22, 2015 1:05 PM, Ø467

Carmelo Evoli, Universität Hamburg [slides]

At GeV-TeV energies the propagation of CRs in our Galaxy is diffusive. Current models of galactic propagation are based on a simplified approach for which diffusion is constant and isotropic. In fact, diffusion transport must be described as in-homogenous and anisotropic and experimental data have now reached an accuracy that allows to study such effects.  

In my talk, I will present some of the consequences of adopting realistic diffusion models for the propagation of galactic CRs, and I will show how these models allow a better understanding of local observations and diffusion emissions within an unified framework.

In the second part of my talk, I will focus on antiprotons as a tool to set constraints on DM models.  In particular, I will discuss the uncertainties associated to both standard astrophysical and DM originated antiprotons. I will show on which extent current antiproton data can place tight constraints on DM models, excluding some of those suggested in connection with indirect and direct searches.

Time and place: Apr. 15, 2015 1:05 PM, Ø467

Marco Cirelli, Saclay, France [slides]

The field of Dark Matter Indirect Detection is in a thriving but somewhat chaotic moment: quite a few hints of possible detection of signals of DM (over a large range of masses and, in general, inferred properties) are confronted with stringent constraints, often based on the same experiments that provide the possible hints. In turn, this spurs a lot of theoretical activity, aimed at phenomenologically analyzing the claims and, perhaps, at embedding them in wider model building. I will briefly review the current status of the searches, mention the most debated hints and sketch the general directions of the theory activity.

Time and place: Mar. 25, 2015 1:05 PM, Ø467

Daniele Gaggero, SISSA, Trieste, Italy  [slides]

In the first part of the talk, after a general introduction on the physics of cosmic rays (CRs), I present a detailed overview on recent results regarding modeling of CR propagation in the Galaxy and in the Heliosphere. In particular I focus on the necessity to go beyond the standard and simplified picture of uniform and homogeneous diffusion, showing that gamma-ray data point towards different propagation regimes in different regions of the Galaxy. I also sketch the impact of large-scale structure on CR observables. Concerning the propagation of the Heliosphere, I mention the necessity to consider a charge-dependent modulation scenario.

In the second part, I discuss several aspects of the recent claim of a gamma-ray excess in the Galactic center region, discussing in particular the interpretation in terms of Dark Matter, compared to other astrophysical interpretations. I will emphasize the interplay between the non-trivial aspects of CR propagation discussed in the first part and the understanding of the GC excess origin. In particular, I will show in detail how the knowledge of the CR transport parameters and solar modulation is crucial to investigate the compatibility with other channels (namely antiprotons) and to provide alternative astrophysical interpretations.

Time and place: Mar. 11, 2015 1:05 PM, Ø467

Susanne Viefers, UiO

In recent years there has been substantial interest in the study of strongly correlated states of cold atoms, analogous to exotic states known from low-dimensional electron systems - one 'holy grail' being experimental realisation of quantum Hall-like states in atomic Bose condensates. In particular there have been many studies on the rotational properties of cold atom systems, as rotation is the conceptually simplest way of simulating a magnetic field for electrically neutral atoms. Even richer physics is expected in the case of two-species gases, such as mixtures of two types of bosonic atoms.

In this talk I will give an introduction to the field, followed by some recent results on the rotational properties of two-species Bose gases in the lowest Landau level. In particular we show that, contrary to expectations, trial wave functions of the composite fermion (CF) type, known from quantum Hall physics, give a very accurate description of this system. It is also shown how working only with a certain subset of possible CF candidate wave functions constitutes a major computational simplification without much loss of accuracy for the low-lying states. Finally I will briefly discuss some striking mathematical identities between seemingly different CF candidate states, of interest for a better understanding of the CF method in general.

Time and place: Feb. 25, 2015 1:05 PM, Ø467

Abram Krislock, UiO

During Supersymmetry phenomenology research, involving simulations of the Large Hadron Collider experiments, a certain mistrust of data analysis using common histograms arose. Someone once said, "Change the bins and try the fit again..." A quest began to eliminate the bins entirely. After a recent study, it was clear that a deeper understanding of statistics was needed to complete this quest. A new probability calculus was discovered, leading to an interesting new data smoothing technique.

Time and place: Feb. 18, 2015 1:05 PM, FØ467

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

Time and place: Jan. 28, 2015 1:05 PM, FØ467

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.
Time and place: Dec. 9, 2014 10:00 AMDec. 11, 2014 1:00 PM, LilleFy
Time and place: Nov. 26, 2014 1:05 PM, FØ467

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.

Time and place: Nov. 6, 2014 1:05 PM, FØ467

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.

Time and place: Nov. 5, 2014 1:05 PM, FØ467

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.

Time and place: Oct. 29, 2014 1:05 PM, FØ467

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.

Time and place: Oct. 22, 2014 1:05 PM, FØ467

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.

Time and place: Oct. 15, 2014 1:05 PM, FØ467

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.

Time and place: Oct. 8, 2014 1:05 PM, FØ467

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.

Time and place: Oct. 1, 2014 1:05 PM, FØ467

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.

Time and place: Sep. 17, 2014 1:05 PM, FØ467

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.
Time and place: Sep. 3, 2014 1:05 PM, FØ467

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? 

Time and place: June 11, 2014 1:05 PM, FØ467

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.