Joint ICTP/SISSA Statistical Physics Seminar, 15 July at 11:00am, by A. Pizzi

[CMSP Seminars Secretariat]

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Joint ICTP/SISSA Statistical Physics Seminar
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** * * Tuesday 15 July**2025, 11:00**am ***(CET)** * **
*Luigi Stasi Seminar Room **(Leonardo Building)***
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/Zoom: 
https://zoom.us/meeting/register/EfoaG7Q1Q6O2VLxf-q1RyA/<https://zoom.us/meeting/register/tJIsfuuhqjsrE9EZY2loNxNobg8Lf39NUVHJ>

Speaker:*Andrea Pizzi *(Christ's College, Cambridge)

Title: *Scars, trails, and ergodicity breaking in chaotic quantum systems**
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Abstract:
At the level of local observables and due to the eigenstate 
thermalization hypothesis (ETH), isolated systems of many interacting 
particles tend to quickly thermalize and forget about their past. This 
paradigm needs not apply to wavefunction amplitudes, objects of 
increasing relevance for modern quantum computers and simulators. Here, 
we unveil the structure of the many-body wavefunction in chaotic spin 
models. Despite the eigenstates fulfilling ETH and being strongly 
entangled, exponentially many of them are genuinely scarred, that is, 
have an enlarged weight along underlying classical unstable periodic 
orbits. Scarring underpins an anomalous (non-Porter-Thomas) statistics 
of the wavefunction amplitudes, and makes the system more likely to be 
found on an orbit it was initialized on, retaining a memory of its past 
and weakly breaking ergodicity. We demonstrate the ubiquity of scarring 
in many-body systems by considering a large family of spin models, 
including some of the most popular ones from condensed matter physics. 
Some features of scarring even extend beyond periodic orbits, giving 
rise to “quantum trails” along generic (non-periodic) trajectories. Our 
findings prove structure in spite of chaos in many-body quantum systems.