Events - Page 27
Ipsita Mandal, Perimeter institute
We devise a renormalization group analysis for quantum field theories with Fermi surface to study scaling behaviour of non-Fermi liquid states in a controlled approximation. The non-Fermi liquid fixed points are identified from a Fermi surface in (m+1) spatial dimensions, while the co-dimension of Fermi surface is also extended to a generic value. We also study superconducting instability in such systems as a function of dimension and co-dimension of the Fermi surface. The key point in this whole analysis is that unlike in relativistic QFT, the Fermi momentum kF enters as a dimensionful parameter, thus modifying the naive scaling arguments. The effective coupling constants are found to be combinations of the original coupling constants and kF.
The slides are now available.
Tomás Gonzalo, University College London
Grand Unified Theories are a very well motivated extension of the Standard Model, but the landscape of models and possibilities is overwhelming, and different patterns present rather distinct and unique phenomenology. We present in this work a way to automatise the model building process, by considering a top-bottom approach that constructs viable and sensible theories from a small and controllable set of inputs at the high scale. By providing a GUT scale symmetry group and the field content, all the possible symmetry breaking paths are generated and checked for consistency, ensuring anomaly cancellation and Standard Model embedding. We emphasise the usefulness of this process for various models such as a Supersymmetric SO(10) model, a non-SUSY left-right symmetry model or a theory of GUT inflation.
(Slides are now available).
The conference aims to promote scientific exchange and the development of novel ideas, with a particular emphasis on interdisciplinarity.
Yong Tang, KIAS
This talk will discuss some possible connections between neutrinos and dark matter, in light of astrophysical observations. Contents include self-interacting dark matter, sterile neutrinos and IceCube Events.
The slides are now available.
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.
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.
The research centre for dark matter, The Strategic Dark Matter Initiative - SDI, will officially be launched on Friday, and invites you all to a popular science lecture, with coffee and snacks.
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.
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.
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.
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.
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.
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.
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.
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.
Each year in spring, research institutes and universities around the world invite high-school students for a day-long programme to experience life at the forefront of basic research. These International Masterclasses give students the opportunity to be particle physicists for a day by analysing real data from the Large Hadron Collider, or LHC, at CERN.
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.
Each year in spring, research institutes and universities around the world invite high-school students for a day-long programme to experience life at the forefront of basic research. These International Masterclasses give students the opportunity to be particle physicists for a day by analysing real data from the Large Hadron Collider, or LHC, at CERN.
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.