ELFT HÍRADÓ

[Somogyi Gábor <somogyi.gabor AT wigner.hun-ren.hu>]

Wigner FK RMI Elméleti Osztály Szemináriuma
Tisztelettel meghívjuk


        Riccarda Bonsignori
        (BME Department of Theoretical Physics)


"Entanglement Hamiltonian after a local quench”


címmel tartandó szemináriumára.


Kivonat:



Understanding the structure of entanglement in extended quantum systems 
is a fundamental problem in theoretical physics. In this framework, a 
central object is the so-called entanglement (or modular) Hamiltonian 
(EH), defined as the logarithm of the reduced density matrix, that 
encodes the full structure of bipartite entanglement. In general the EH  
is very hard to compute and is not even expected to be a local 
operator.  However, in relativistic quantum field theory the locality of 
the modular Hamiltonian for half-space bipartitions is ensured by the 
Bisognano–Wichmann theorem, which expresses it as an integral of the 
energy density with a linear spatial weight. In the presence of 
conformal symmetry, this result can be extended to other geometries and 
to some non-equilibrium settings. Since the Bisognano–Wichmann theorem 
is formulated within relativistic quantum field theory, a natural 
question concerns its applicability to lattice many-body systems whose 
low-energy properties are described by a conformal field theory, but 
which explicitly break Lorentz invariance. Several results addressing 
this question exist in equilibrium situations, while a lattice 
realisation of the time-dependent EH in out-of-equilibrium dynamics is 
still missing.
In this talk, I will present the study of the dynamics of the EH in a 
system of one-dimensional free fermions, following a local joining 
quench of two initially disconnected half-chains in their ground states. 
Applying techniques of conformal field theory, a local expression of the 
EH is derived, where the left- and right-moving components of the energy 
density are associated with different weight functions.
The results are then compared to numerical calculations for the hopping 
chain, which requires to consider a proper continuum limit of the 
lattice EH, obtaining a good agreement with the field-theory prediction.

Based on: R. Bonsignori and V. Eisler, J. High Energ. Phys. 2026, 232 
(2026).



Helye: Wigner FK RMI III. ép. Tanácsterem
Ideje: 2026 április 17. péntek d.u. 2 óra

Szívesen látunk minden érdeklődőt.


                  Somogyi Gábor