Polls Martí, ArturPons Mojena, Marina2018-10-092018-10-092018-06https://hdl.handle.net/2445/125194Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2018, Tutor: Artur PollsWe consider a system of N fermions described by the Lipkin model and investigate their behaviour at finite temperature. We study the in uence of the interactions on thermodynamic properties. The calculations have been done by a numerical diagonalization of the Hamiltonian. Once the full spectrum is known we consider the thermal occupation of the states and calculate the different thermodynamic properties. The extension of the Hellmann-Feynman theorem at finite temperature requires the derivative of the free energy instead of the internal energy used for zero temperature. The importance of the entropy in the fullfilment of the Hellmann-Feynman theorem is analyzed5 p.application/pdfengcc-by-nc-nd (c) Pons, 2018http://creativecommons.org/licenses/by-nc-nd/3.0/es/FermionsNivells d'energia (Mecànica quàntica)Treballs de fi de grauFermionsEnergy levels (Quantum mechanics)Bachelor's thesesinfo:eu-repo/semantics/bachelorThesisinfo:eu-repo/semantics/openAccess