• symmetry-resolved entanglement entropy
• entanglement entropy
• conformal field theory

Entanglement is a fundamental concept in quantum mechanics, with applications in many different fields.
There are many ways to quantify entanglement, a very convenient one for bipartite systems at zero temperature being the entanglement entropy, which is the one considered in this manuscript. The goal of this thesis is to study the behavior of entanglement in a many-body system with an internal global symmetry, more specifically a system of one dimensional free Dirac fermions with U (1) symmetry.
In the first chapters, previous results in the literature regarding these topics are presented, along with basic techniques and relations used throughout the thesis.
Chapters 5 and 6 are the core of the thesis, and present explicit expressions regarding the symmetry-resolved entanglement entropy of Dirac Fermions at finite temperature and size. These expressions are plotted and compared with exact lattice computation.
While chapter 5 deals with massless fermions, in chapter 6 the leading massive correction is considered, extending the previous result in the vicinity of a critical point.
An analysis of the charge dependence on the calculated entanglement entropy shows that this quantity is equally distributed between all the symmetry sectors
at the leading order.