Organisation des séminaires et calendrier

I will derive the analytic structure of the S-matrix for classical wave scattering on a Schwarzschild black hole in 4-dimensions. The argument relies on the analytic continuation of the gravitational potential, with the singularity behind the horizon playing a crucial role. We observe the emergence of Stokes phenomena leading to a surprising branch cut in the upper half plane, seemingly in tension with causality. I will discuss how this apparent paradox is solved and mention some bootstrap applications of these results.

Abstract: 

There is an intriguing robustness in certain statistical patterns describing the dynamics and organization of seemingly very different ecosystems, spanning scales from trees in a rainforest to bacteria in the human gut.

These patterns motivate several common questions: How can so many ecologically similar species coexist locally? Why does only a small fraction of these coexisting species typically account for most of the total biomass? What drives changes in the identity of these dominant species across space and time?

In this lecture, I will give an account of recent work at the intersection of statistical physics and theoretical ecology that aims to address these questions. Emphasis will be placed on disordered-systems approaches, which provide a natural theoretical framework without committing to any specific ecosystem.

Topics covered include:

• Common patterns in the organization and dynamics of species-rich ecosystems
• Disordered Lotka-Volterra-like models and Dynamical Mean-Field Theory
• Models for the coexistence of spatially extended populations
• Inverse stability-complexity relationship in the presence of environmental disorder

Please check the IPhT courses website courses.ipht.fr for last-minute changes in the schedule.
To receive the latest news on this course and the video-conference links, please subscribe to its newsletter, as explained at the courses website.
An open, non-interactive livestream will also be available at youtube.com/ipht-tv

TBA

Abstract: 

There is an intriguing robustness in certain statistical patterns describing the dynamics and organization of seemingly very different ecosystems, spanning scales from trees in a rainforest to bacteria in the human gut.

These patterns motivate several common questions: How can so many ecologically similar species coexist locally? Why does only a small fraction of these coexisting species typically account for most of the total biomass? What drives changes in the identity of these dominant species across space and time?

In this lecture, I will give an account of recent work at the intersection of statistical physics and theoretical ecology that aims to address these questions. Emphasis will be placed on disordered-systems approaches, which provide a natural theoretical framework without committing to any specific ecosystem.

Topics covered include:

• Common patterns in the organization and dynamics of species-rich ecosystems
• Disordered Lotka-Volterra-like models and Dynamical Mean-Field Theory
• Models for the coexistence of spatially extended populations
• Inverse stability-complexity relationship in the presence of environmental disorder

Please check the IPhT courses website courses.ipht.fr for last-minute changes in the schedule.
To receive the latest news on this course and the video-conference links, please subscribe to its newsletter, as explained at the courses website.
An open, non-interactive livestream will also be available at youtube.com/ipht-tv

We study the long-time, large-distance asymptotic behaviour of dynamical two-point correlation functions of the Lieb–Liniger model in the limit of infinite repulsion (the one-dimensional impenetrable Bose gas). Starting with exact representations of correlation functions in terms of Fredholm determinants of an integrable integral operator, we perform the rigorous asymptotic analysis, using Riemann–Hilbert techniques. The integral operator
depends parametrically on time \(t\), distance \(x\) and on the filling fraction — a function that characterizes the thermal or non-thermal equilibrium conditions. We consider a large class of non-thermal equilibrium conditions, extending previous results established for the thermal equilibrium case. The long-time and large-distance asymptotic behaviour is derived for two classes of filling fractions. These classes are characterized by the number of poles on the real axis (a generalization of Fermi points) that, together with the unique saddle point, contribute to the asymptotic expansion. For each class, we derive the long-time, large-distance symptotic behaviour as a series in \(x\)^\(−1/2\) as \(x\) and \(t\) go to infinity for a fixed ratio \(x/t\). We provide explicit closed-form expressions for the leading and sub-leading terms, logarithmic corrections, and overall constants in terms of special functions and simple integrals. For the impenetrable Bose gas in thermal equilibrium, we verify the derived asymptotic expansions by comparing them with the existing results in the literature and with numerical data.
This talk is based on joint work with Frank Göhmann, Karol K. Kozlowski, and Alexander Weiße.

Abstract: 

There is an intriguing robustness in certain statistical patterns describing the dynamics and organization of seemingly very different ecosystems, spanning scales from trees in a rainforest to bacteria in the human gut.

These patterns motivate several common questions: How can so many ecologically similar species coexist locally? Why does only a small fraction of these coexisting species typically account for most of the total biomass? What drives changes in the identity of these dominant species across space and time?

In this lecture, I will give an account of recent work at the intersection of statistical physics and theoretical ecology that aims to address these questions. Emphasis will be placed on disordered-systems approaches, which provide a natural theoretical framework without committing to any specific ecosystem.

Topics covered include:

• Common patterns in the organization and dynamics of species-rich ecosystems
• Disordered Lotka-Volterra-like models and Dynamical Mean-Field Theory
• Models for the coexistence of spatially extended populations
• Inverse stability-complexity relationship in the presence of environmental disorder

Please check the IPhT courses website courses.ipht.fr for last-minute changes in the schedule.
To receive the latest news on this course and the video-conference links, please subscribe to its newsletter, as explained at the courses website.
An open, non-interactive livestream will also be available at youtube.com/ipht-tv

Intervenante: Angèle Lochet

Nous expliquerons pas à pas comment les caractéristiques physiques d’un trou noir ont mené à un paradoxe, appelé paradoxe de l’information. Notamment, nous mettrons l’accent sur ce que nous appelons information, qui est souvent source d’incompréhension. Si le temps le permet, nous verrons des pistes de résolution de ce paradoxe.

Abstract: 

There is an intriguing robustness in certain statistical patterns describing the dynamics and organization of seemingly very different ecosystems, spanning scales from trees in a rainforest to bacteria in the human gut.

These patterns motivate several common questions: How can so many ecologically similar species coexist locally? Why does only a small fraction of these coexisting species typically account for most of the total biomass? What drives changes in the identity of these dominant species across space and time?

In this lecture, I will give an account of recent work at the intersection of statistical physics and theoretical ecology that aims to address these questions. Emphasis will be placed on disordered-systems approaches, which provide a natural theoretical framework without committing to any specific ecosystem.

Topics covered include:

• Common patterns in the organization and dynamics of species-rich ecosystems
• Disordered Lotka-Volterra-like models and Dynamical Mean-Field Theory
• Models for the coexistence of spatially extended populations
• Inverse stability-complexity relationship in the presence of environmental disorder

Please check the IPhT courses website courses.ipht.fr for last-minute changes in the schedule.
To receive the latest news on this course and the video-conference links, please subscribe to its newsletter, as explained at the courses website.
An open, non-interactive livestream will also be available at youtube.com/ipht-tv

After describing elastic interactions and the discovery of the odderon by the TOTEM and D0 Collaborations, we will discuss new kinematical regimes where the gluon density in the proton or Pb can be very large which leads to new equations in Quantum Chromodynamics.  We will also present the latest expectations on beyond standard model physics and especially the production of axion-like particles using intact protons after the collision.  We will finish by describing briefly the Low Gain Avalanche Detectors and their applications in medicine for cancer treatment and with NASA to measure cosmic rays.