Spontaneous symmetry breaking and response functions

Spontaneous symmetry breaking and response functions

We study the quantum phase transition occurring in an infinite homogeneous system of spin 1/2 fermions in a non-relativistic context. As an example we consider neutrons interacting through a simple spin-spin Heisenberg force. The two critical values of the coupling strength — signaling the onset into the system of a finite magnetization and of the total magnetization, respectively — are found a...

Se p 20 04 Spontaneous symmetry breaking and response functions

We study the quantum phase transition occurring in an infinite homogeneous system of spin 1/2 fermions in a non-relativistic context. As an example we consider neutrons interacting through a simple spin-spin Heisenberg force. The two critical values of the coupling strength — signaling the onset into the system of a finite magnetization and of the total magnetization, respectively — are found a...

Nonperturbative Spontaneous Symmetry Breaking

One of the most astonishing results of quantum field theory is spontaneous symmetry breaking. One can say that it is the situation when something arises from the quantization. This means that on the quantum level one has something that was not present on the classical level. Coleman and Weinberg [1] write : “ . . . higher-order effects may qualitatively change the character of a physical theory...

Spontaneous Symmetry Breaking

Decoherence induced spontaneous symmetry breaking

We study time dependence of exchange symmetry properties of Bell states when two-qubits interact with local baths having identical parameters. In case of classical noise, we consider a decoherence Hamiltonian which is invariant under swapping the first and second qubits. We find that as the system evolves in time, two of the three symmetric Bell states preserve their qubit exchange symmetry wit...