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Physics Colloquium Series

Physics Colloquium presents a venue for the latest developments in all branches of physics in a way accessible to non-expert physicists. The monthly Physics Colloquia take place on selected Wednesdays at 4:30 pm in the Conference Hall of the main Farmanieh building, with an announcement circulated in advance. Please forward your suggestions for potential Colloquium speakers to jabbari(at)theory.ipm.ac.ir. To subscribe to the Colloquium mailing list, please send an email with the subject line "subscribe me to physics colloquium" to physoffice(at)theory.ipm.ac.ir.

Wed May 10, 2023 (1402/2/20)

	May 10 1402/2/20	18:00	Uncovering hidden neuronal microcircuits using Boltzmann like correlations, a unified framework Show Abstract Abstract:The information transfer and processing in our brain relies on cells called neurons. They are connected to each other through connections called synapse, and form an interconnected complex network, known as gray matter. Each neuron receives signals from its upstream neurons, generates a spike, and passes it to many downstream neurons. To understand this complex structure, one should have learnt the connectivity map of neurons, in a living brain. However, it is practically impossible to record from one neuron and all its hidden inputs to determine the influential synapses which dominate the activity of that neuron. Although there are methods to find the connectivity among recorded (observed) neurons, the majority of downstream neurons remain unobserved. Here, we find the analytical input-output relation which describes how a specific input to a neuron controls statistics of its spiking pattern. Then, using this analytics, we connect the hidden microcircuits which are shared by two or more neurons with the observed correlation between their spiking patterns. We present a guide map in the space of neural interactions (i.e pairwise and triple-wise correlations) to infer the influential hidden circuits from data. We verify the validity of the guide map by extensive simulations, using multicompartmental neuron models of Blue Brain Project. Applying the guide map to monkey and mouse, we observed the hidden circuitry of excitatory inputs shared between each pair of three neurons is the motif behind most of the data. We hope experimentalists use our guide-map, to reveal the hidden microcircuits behind their data. Lecturer(s): Seyyed Nader Rasuli From : IPM, School of Physics Research Group: Physics Colloquium More Info. : Link
Wed Apr 06, 2022 (1401/1/17)

	Apr 06 1401/1/17	18:00	Uncovering Energetic Processes in the Interstellar/Intergalactic Medium with the Square Kilometre Array Show Abstract Abstract:Investigating the physics and energetic of the medium where galactic structures, on various scales, are formed is the most fundamental step to understand the formation and evolution of galaxies. Modern galaxy evolution models suggest gas accretion from the intergalactic medium (IGM) or from cosmic filaments as a mechanism to maintain star formation and active galactic nucleus (AGN). Through gas heating and/or gas removal, these models also propose supernova feedback and AGN feedback as mechanisms to quench massive star formation. Observational studies, however, have not reached to a conclusive result showing that feedback can, in some cases, trigger star formation, leaving the issue as an open challenge. It seems that some basic concepts about the formation of structures in the interstellar medium (ISM) and the IGM are missed: What are physical parameters/agents governing the structure formation on various scales? How does the ISM/IGM energy balance change over cosmic time? The advent of the square kilometre array (SKA) and its instrumental capabilities tracing the most energetic ISM components has opened a new window shedding light on the issue. The SKA's sensitive radio continuum observations will trace high-energy particles and magnetic fields not only in star forming regions and AGNs, but also in more quiescent regions in molecular clouds and diffuse IGM, enabling us to study the role of magnetic fields/cosmic rays in structure formation. Sensitive radio continuum observations on large scales may also bring constrains on the entity of dark matter mapped by the Hubble Space Telescope (HST) and Dark Energy Camera (DECam). Lecturer(s): Fatemeh Tabatabaei From : IPM, School of Astronomy Research Group: Physics Colloquium More Info. : Link
Wed Mar 02, 2022 (1400/12/11)

	Mar 02 1400/12/11	18:00	Dance of Cause and Effect: Fluctuation Induced Reduction of Dissipation in Classical Fluids Show Abstract Abstract:About seventy years ago, G I Taylor noticed that the tails of two closely swimming spermatozoa, oscillate in a synchronized fashion as if both of them are controlled from one regulating center. The two sperms, on the other hand, has no mean of communication, but the viscous fluid in which they are swimming. To address the why question, behind the observation, he suggested the minimization of total dissipation in the viscous medium. Sixty years later, Taylors original idea was put to more detailed analytical investigations; non-intuitively, it failed to attribute the observed synchronization to the expected reduction of dissipation. We begin with a very different problem: (a) The motion of two passively trapped beads, which interact through hydrodynamic interactions, and face a driven flow. Both theoretically and experimentally we observe that they almost follow the very motion they would have, if they were to swim on their own in the opposite direction of the driven flow. Calling the phenomenon, the reverse dance, we successfully attribute it to the reduction of the total dissipation. We then (b) extend the minimalistic approach, to two sets of beads; each supposed to mimic the tail of one spermatozoon. Facing a driven flow, on top of their intrinsic oscillation, this is a minimalistic model to verify Taylors idea. The question is, does this simple model lead us to synchronization as well as reduction of fluids dissipation? And if so, can it explain why Taylors original model failed to correctly attribute synchronization with reduction of dissipation? Lecturer(s): Seyyed Nader Rasuli From : University of Guilan & School of Physics, IPM Research Group: Physics Colloquium More Info. : Link
Wed Feb 02, 2022 (1400/11/13)

	Feb 02 1400/11/13	18:19	Einstein vs Einstein: The Great War Show Abstract Abstract:Within the span of seven months in the midst of the Great War, Albert Einstein published two seminal papers, on "Quantum Emission and Absorption" and "Field Equations of Gravitation", that laid the foundations of modern physics. Our century-long odyssey starts here, taking us through the rise of holography, fuzzballs, firewalls, quantum chaos, and gravitational wave astronomy. However, in the end, it will land us back within those fateful seven months, where Einstein's July 1916 "Strahlungs-Emission und -Absorption nach der Quantentheorie" may prove to be the ultimate undoing of his December 1915 "Die Feldgleichungen der Gravitation". I will lay down the theoretical and observational arguments on both sides of (the latest battle) in Einstein's Great War. Lecturer(s): Niayesh Afshordi From : Department of Physics and Astronomy, University of Waterloo Research Group: Physics Colloquium More Info. : Link
Wed Jan 05, 2022 (1400/10/15)

	Jan 05 1400/10/15	18:00	On Progress in Scientific Theories Show Abstract Abstract:Thomas Kuhn's "theory of scientific revolutions" describes evolution in sciences from a socio-historic viewpoint, wherein paradigm shift happens as a result of a scientific revolution. According to this theory paradigm shifts are not oriented, there is no progress in scientific paradigms. In this seminar, I critically review Thomas Kuhn's theory and introduce the notion of "hyper-theory" instead of paradigm. We then discuss that not only there are meaningful ratings for scientific models, but there is also a notion of progress in theories and hyper-theories. I present and state "model of progression scientific theories" instead of Kuhn's theory. Lecturer(s): M. M. Sheikh-Jabbari From : IPM, School of Physics Research Group: Physics Colloquium More Info. : Video Link
Wed Feb 05, 2020 (1398/11/16)

	Feb 05 1398/11/16	16:00	Fundamental Successes and Challenges of the Contemporary Physics Abstract Lecturer(s): Mehdi Golshani From : Sharif University of Technology & IPM Research Group: Physics Colloquium Farmanieh Conference Hall
Wed Dec 11, 2019 (1398/9/20)

	Dec 11 1398/9/20	16:00	Primordial Universe and Cosmic Inflation Abstract Note Audio File Lecturer(s): Hassan Firouzjahi From : IPM, School of Astronomy Research Group: Physics Colloquium Farmanieh Conference Hall
Wed Nov 20, 2019 (1398/8/29)

	Nov 20 1398/8/29	16:00	The Higgs Boson program at the LHC and future colliders Abstract Lecturer(s): Mojtaba Mohammadi Najafabadi From : IPM, School of Particles and Accelerators Research Group: Physics Colloquium Farmanieh Conference Hall
Wed Mar 06, 2019 (1397/12/15)

	Mar 06 1397/12/15	16:30	"Landau and Ginzburg" remove tensions between "Planck" and "Hubble and Lyman" Abstract Lecturer(s): Nima Khosravi From : Shahid Beheshti Univ. & IPM Research Group: Physics Colloquium Farmanieh Seminar Room
Wed Jan 30, 2019 (1397/11/10)

	Jan 30 1397/11/10	16:30	Does String Theory Avoid Its Own Swampland? Abstract Lecturer(s): Mohammad Mehdi Sheikh-Jabbari From : IPM, School of Physics Research Group: Physics Colloquium Farmanieh Seminar Room
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