HELSINKI INSTITUTE OF PHYSICS SEMINARS
HIP seminar room A315
- Tuesday 12 March 2019 at 10.15 in A315: Matteo Baggioli (Madrid)
Holographic viscoelastic phases of matter: from fluids to solids and more
Abstract: Holographic techniques have been widely and successfully used to describe strongly coupled fluids. In this talk I will review how bottom-up holographic models can be extended to include also solid and especially viscoelastic phases of matter. I will show how to formalize the (visco)-elastic response and I will discuss in details the vibrational phononic degrees of freedom from an holographic perspective. Finally I will apply the formalism to several condensed matter open questions. If time permits:
1) I will show the connections to the effective field theory (EFT) methods
2) I will discuss also how these ideas have triggered relevant developments in soft matter theory and experiments dealing with the glassy anomalies and the low frequency elastic response in liquids.
No detailed knowledge of AdS-CMT methods is required and lot of low energy condensed matter will be present.
- Tuesday 19 March 2019 at 10.15 in A315: Chitta Das (JINR)
Octant of θ23 in neutrino mixing and beyond the Standard Model
Abstract: The prospect for resolving the octant of the neutrino mixing angle θ23, that is, whether the atmospheric mixing angle is in higher octant (θ23 > 45°) or in lower octant (θ23 < 45°), in future long baseline neutrino experiments, will be explained in this talk. We found out, long baseline experiments measuring the νμ→νe transition probability are capable of resolving this degeneracy, also we present the importance of the matter effects with baseline length in the determination of the octant with the GLoBES software. We have shown how runtime ratio in neutrino and anti-neutrino modes contribute to the octant determination. The sensitivity to θ23 octant is shown as contour plots on the (θ23−45°, δ)-plane, where δ is the CP phase in the neutrino mixing matrix. We demonstrate the true values of θ23 for which the octant can be experimentally determined with a 5σ certainty level and the interference on the octant determination that arises from the unconstrained CP violation angle δ. In our results, we establish a connection between the beam sharing and mass hierarchy, in particular, we numerically derived the sensitivity limits of the possible non-unitarity of neutrino mixing on the experimental determination of θ23.
- Thursday 25 April 2019 at 10.15 in A315: Ville Vaskonen (King’s College)
Primordial black holes in the light of LIGO observations
Abstract: The observation of gravitational waves from black hole mergers by LIGO has revived the interest in the possibility of primordial black hole (PBH) dark matter. In this talk I will, after a short introduction to PBH formation and constraints, describe how PBH binaries are formed in the early universe and discuss their evolution. Finally, I will use the merger rate estimates and the LIGO observations to put constraints on the PBH abundance, and show that the observed merger rate can be explained by PBHs forming O(0.1%) of dark matter with a narrow mass distribution around 20 solar masses.
- Tuesday 30 April 2019 at 10.15 in A315: Carlos Hoyos (Oviedo)
Effective long distance q-qbar potential in holographic RG flows
Abstract: We study the q -qbar potential in strongly coupled non-conformal field theories with a non-trivial renormalization group flow via holography. We focus on the properties of this potential at an inter-quark separation L large compared to the characteristic scale of the field theory. These are determined by the leading order IR physics plus a series of corrections, sensitive to the properties of the RG flow. To determine those corrections, we propose a general method applying holographic Wilsonian renormalization to a dual string. We apply this method to examine in detail two sets of examples, 3+1-dimensional theories with an RG flow from an IR fixed point driven by an irrelevant deformation; and theories that are confining in the IR. We discuss the physical interpretation of these results and how could they be used to check our understanding of confinement in gauge/gravity duals using lattice QCD.
- Thursday 27 June 2019 at 10.15 in A315: Suvankar Dutta (IISER Bhopal India)
- Tuesday 27 August 2019 at 10.15 in A315: Tommi Tenkanen (Johns Hopkins University)
Spectator Dark Matter
Abstract: The observed dark matter abundance in the Universe can be fully accounted for by a minimally coupled spectator scalar field that was light during inflation and has sufficiently strong self-coupling. In this scenario, dark matter was produced during inflation by amplification of quantum fluctuations of the spectator field. The self-interaction of the field suppresses its fluctuations on large scales, and therefore avoids isocurvature constraints. The scenario does not require any fine-tuning of parameters. I will also discuss ways to test the scenario.
Hopefully the up to 50 min + 10 min discussion long seminar/colloquium will be understandable to a wide audience.
Contacts: Keijo Kajantie (keijo kajantie at helsinki fi) [ HIP seminar],
Sofie Koksbang (sofie koksbang at helsinki fi) [cosmo seminar]
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