Program Archive of the Ortvay Seminar Series 2017 Spring

2017. február 2. csütörtök 15:00-kor
2nd February 2017., Thursday 3pm

Francois Mernier (SRON Netherlands Institute for Space Research, Leiden University)

From supernovae to galaxy clusters: the chemical enrichment of the intra-cluster medium seen by XMM-Newton

Abstract:

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2017. február 16. csütörtök 15:00-kor
16th February 2017., Thursday 3pm

Kolláth Zoltán (ELTE Savaria Egyetemi Központ)

A Szombathelyi Fizika Tanszék bemutatása -- van egy új tanszékünk


2017. február 23. csütörtök 15:00-kor
23rd February 2017., Thursday 3pm

Derényi Imre (ELTE-TTK Biológiai Fizika Tanszék)

Az új fizika BSc bemutatása


2017. február 23. csütörtök 16:00-kor
23rd February 2017., Thursday 4pm

Sijbrand de Jong (President of CERN Council, Radboud University Nijmegen)

Radio detection: a new observation technique to inv

Abstract:

Ultra-High-Energy Cosmic Rays (UHECRs) have been found with energies as high as 1020 eV in a single subatomic particle. The 3000 km2 Pierre Auger Observatory has collected data over the past 15 years that confirmed a predicted cut-off at ultra-high energy. However, it also introduced new mysteries surrounding these UHECRs. At this moment we must admit that we do not know their sources, their propagate through the universe, or even their particle type is.

The detection of UHECRs using the radio frequency signals they produce in the atmosphere, which was developed over the last decade, is a new and powerful tool to solve the current mysteries surrounding UHECRs. In this talk I will introduce the open questions on UHECRs and discuss the mechanism, status and prospects for radio detection of UHECRs.


2017. március 2. csütörtök 15:00-kor
2nd March 2017., Thursday 3pm

Takács Gábor (BME Dept. of Theoretical Physics, MTA-BME Statistical Field Theory Research Group)

Dynamical confinement in out-of-equilibrium quantum systems

Abstract:

Non-equlibrium quantum systems have recently come to the fore in theoretical physics, mainly due to the rapid development of experimental techniques. The interest is partly motivated by fundamental theoretical problems: what are the conditions for a closed non-equilibrium quantum system to evolve towards an equilibrium, and what is the nature of an eventual equilibrium state? Another reason is that a large number of exotic quantum phenomena, hitherto only predicted or known theoretically, have been realised in the lab, which allows for directly comparing the models to physics reality.


2017. március 9. csütörtök 15:00-kor
9th March 2017., Thursday 3pm

Bill Poirier (Texas Tech University, Lubbock TX)

Quantum Mechanics without Wavefunctions

Abstract:

Seven years ago, the first paper was published [1] on what has come to be known as the “Many Interacting Worlds” (MIW) interpretation of quantum mechanics (QM) [2]. MIW is based on a new formulation of QM [1,3], in which the wavefunction Ψ(t, x) is discarded entirely. Instead, the quantum state is represented as an ensemble, x(t, C), of quantum trajectories or “worlds,” each of which has well-defined real-valued particle positions and momenta. The worlds interact, giving rise to all quantum behavior observed in nature. MIW offers insight into quantum phenomena such as entanglement, measurement, spontaneous decay, etc. Moreover, x(t, C) satisfies a trajectory-based action principle, which allows quantum theory (via Euler-Lagrange and Noether) to be placed on the same footing as classical (Newtonian and relativistic [4]) theories. Other benefits will also be discussed.

[1] B. Poirier, Chem. Phys. 370, 4 (2010).
[2] B. Poirier, Phys. Rev. X, 4, 040002 (2014).
[3] J. Schiff and B. Poirier, J. Chem. Phys. 136, 031102 (2012).
[4] B. Poirier, arXiv:1208.6260 [quant-ph], (2012).


2017. március 23. csütörtök 15:00-kor
23rd March 2017., Thursday 3pm

Rózsa Balázs (Laboratory of 3D functional network and dendritic imaging, Institute of Experime ntal Medicine, HAS, The Faculty of Information Technology, Pázmány Péter Catholic University)

Fast 3D acousto-optical imaging of visual computation at the level of spine, dendritic, and neuronal assemblies in behaving mice

Abstract:

Gergely Szalay1*, Linda Judák1*, Gergely Katona1,3*, Pál Maák4, Katalin Ócsai3, Ta más Tompa2, Balázs Rózsa1,2
1. Laboratory of 3D functional network and dendritic imaging, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest-1083, Hungary.*
2. The Faculty of Information Technology, Pázmány Péter Catholic University, Budapest-1083, Hungary.*
3. MTA-PPKE ITK-NAP B – 2p measurement technology group, The Faculty of Information Technology, Pázmány Péter Catholic University, Budapest-1083, Hungary. *
4. Department of Atomic Physics, Budapest University of Technology and Economics, Budapest-1111, Hungary.

Our long-term aim is to assess the feasibility of creating an “ artificial sense” and, thereby, a possible sensory (visual) prosthetic. While working towards this goal, we have to address the question of how neural assembly activity relates to subjective perceptions and visual computation. Finding and understanding these functional dendritic and neuronal assemblies makes it possible to reactivate them in a precise, biologically relevant manner to elicit similar cortical activation as visual stimulation. To achieve this goal we developed a novel method for fast 3D imaging and 3D photo-stimulation which is orders of magnitude more effective and faster than the methods used previously.

The precisely timed and anatomically structured input activity of cortical neurons is nonlinearly transformed to neuronal output by the somatic and dendritic compartments of downstream neurons (Katona et al., 2011; Larkum et al., 2009; Losonczy and Magee, 2006, Poirazi et al., 2003; Polsky et al., 2004; Johnston and Narayanan, 2008). Nonlinear dendritic processing is achieved mainly by voltage-gated ion channels, which interact through locally propagating and attenuating membrane potential fluctuations; in this way, dendritic signal integration can be clustered in small dendritic computational subunits (‘‘hot spots’’). When more synaptic inputs are activated in synchrony, voltage-gated ion channels can also induce more global signals, i.e., regenerative dendritic spikes (Larkum et al., 2009; Schiller et al., 2000; Stuart et al., 1999). In this way, coding and computation within neuronal networks are generated not only by the somatic integration domains, but also by highly non-linear dendritic integration centers that, in most cases, remain hidden from somatic recordings. Therefore, understanding the complexity of visual computation requires novel methods such as three-dimensional (3D) random-access point scanning that can simultaneously read out neural activity on both the somatic and dendritic scales (Duemani Reddy et al., 2008; Katona et al., 2012; Fernandez-Alfonso et al., 2014, Chiovini et al. 2016, Neuron). This method can increase measurement speed and signal-to-noise ratio by several orders of magnitude, but suffers from one main disadvantage: fluorescence information is lost during brain movement. In this work we also present a novel technology, 3D drift acousto-optical scanning, which can extend each scanning point to small 3D lines or surface or volume elements, preserving fluorescence information for motion correction. Our method effectively eliminates *in vivo* motion artifacts, allowing fast 3D measurement of over 150 dendritic spines with 3D lines, over 100 somata with squares and cubes, or multiple spiny dendritic segments with surface and volume elements in moving animals. Moreover, an over of four-fold improvement in total excitation efficiency resulted in a large, about 500µm × 500µm × 900µm, scanning volume with GECIs. Using our new 3D imaging and photo-stimulation methods we mapped activity of large neuronal and dendritic assemblies associated with different visual stimulation and found a new dendritic computational rule with which group of dendritic and neuronal assemblies code time in the visual cortex. Moreover, we revealed how the upcoming cholinergic input pathway from nucleus basalis can generate a broadcasted signal in the cortex by activating the VIP neuronal population and, therefore, generate enchanted dendritic activity and dendritic spikes thorough disinhibition in pyramidal neurons in V1 of behaving animals.


2017. március 30. csütörtök 15:00-kor
30th March 2017., Thursday 3pm

Simon Portegies Zwart (Leiden Observatory, Leiden University)

Solar System forensics: the case of the missing planetesimals

Abstract:

Did the Solar System experience an encounter with another star, some 4 billion years ago? Evidence for such an encounter is possibly preserved in the orbits of planetesimals between the Kuiper belt and the Oort cloud. The planetesimal Sedna provides the key evidence for this encounter, and its consequences.

The moment that this star passes the Solar System roughly corresponds to the moment the procaryotes emerged on Earth. The encounter could also have truncated the outer edge of the Solar System, leading to the Kuyper cliff, and which is required to explain the epoch of Late Heavy Bombardment on the Lunar surface.


2017. április 6. csütörtök 15:00-kor
6th April 2017., Thursday 3pm

Richard J. Szabo (Maxwell Institute for Mathematical Sciences)

Deformations of quantum theory

Abstract:

Theoretical approaches to quantum gravity suggest that the conventional notions of space and time become meaningless at ultra-short distance scales. In many instances, dynamics in such ensuing "fuzzy" spacetimes can be captured by certain deformations of quantum mechanics and quantum field theory. In this lecture I will explain some of the progress that has been achieved over the years in understanding such deformed quantum theories and how they may teach us something about the short-scale structure of spacetime, and ultimately quantum gravity. I will emphasise how these theoretical consequences can connect to real-world measurable quantities, and analyse in detail a simple deformation of quantum mechanics which may be realised in a table-top experiment. From the theoretical side, I will explain how these quantum systems are related to the nonassociative algebras of observables proposed in the beginnings of quantum mechanics and quantum field theory by Jordan, von Neumann, Wigner and others to study the mathematical and conceptual foundations of quantum theory.


2017. április 27. csütörtök 15:00-kor
27th April 2017., Thursday 3pm

Török János (-)

What does Big data tells us about the social networks

Abstract:

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2017. május 4. csütörtök 15:00-kor
4th May 2017., Thursday 3pm

Gergely J. Szöllősi (ELTE, Biológiai Fizika Tanszék)

Gene transfers, like fossils, can date the tree of life

Abstract:

The geological record provides the only source of absolute time information to date the tree of life. But most life is microbial, and most microbes do not fossilize, leading to major uncertainties about the ages of microbial groups and the timing of some of the earliest and most important events in life's evolutionary history. I discuss our recent results, which show that patterns of lateral gene transfer deduced from analysis of modern genomes encode a novel and highly informative source of information about the temporal coexistence of lineages throughout the history of life. We use new phylogenetic methods to reconstruct the history of thousands of gene families and show that dates implied by gene transfers are strongly correlated with estimates from relaxed molecular clocks in Bacteria, Archaea and Eukaryotes. A comparison with mammalian fossils shows that gene transfer in microbes is potentially as informative for dating the tree of life as the geological record in macroorganisms.


2017. május 25. csütörtök 15:00-kor
25th May 2017., Thursday 3pm

Szalay Sándor (The Johns Hopkins University, az ELTE tiszteletbeli doktora és professzora)

The New Astronomy - The Era of Surveys
/Marx Memorial Lecture/

Abstract:

The talk will present an overview how astronomy has changed over the last few decades. Observations make increased use of large-scale surveys, in almost every wavelength of the optical spectrum. Large areas of the sky are covered, and the joint analysis of these multi-wavelength observations are becoming the norm. The wealth of Big Data has also changed the precision of theoretical calculations, and now cosmological theory and observation are within a few percent - we are in the era of precision cosmology. Even particle physics is now highly constrained by astronomy, e.g. the best limits on the neutrino mass are coming from cosmological observations of large scale structure. This New Astronomy requires a new set of skills, scientists must be equally at home in theory, observational techniques, statistics and data analysis skills.