49 research outputs found
Spontaneous Breaking of Lorentz Symmetry and Vertex Operators for Vortices
We first review the spontaneous Lorentz symmetry breaking in the presence of
massless gauge fields and infraparticles. This result was obtained long time
ago in the context of rigorious quantum field theory by Frohlich et. al. and
reformulated by Balachandran and Vaidya using the notion of superselection
sectors and direction-dependent test functions at spatial infinity for the
non-local observables. Inspired by these developments and under the assumption
that the spectrum of the electric charge is quantized, (in units of a
fundamental charge e) we construct a family of vertex operators which create
winding number k, electrically charged Abelian vortices from the vacuum (zero
winding number sector) and/or shift the winding number by k units. In
particular, we find that for rotating vortices the vertex operator at level k
shifts the angular momentum of the vortex by k \frac{{\tilde q}}{q}, where
\tilde q is the electric charge of the quantum state of the vortex and q is the
charge of the vortex scalar field under the U(1) gauge field. We also show
that, for charged-particle-vortex composites angular momentum eigenvalues shift
by k \frac{{\tilde q}}{q}, {\tilde q} being the electric charge of the
charged-particle-vortex composite. This leads to the result that for
\frac{{\tilde q}}{q} half-odd integral and for odd k our vertex operators flip
the statistics of charged-particle-vortex composites from bosons to fermions
and vice versa. For fractional values of \frac{{\tilde q}}{q}, application of
vertex operator on charged-particle-vortex composite leads in general to
composites with anyonic statistics.Comment: Published version, 15+1 pages, 1 figur
O Experimento na balança: lições de alguns eventos de 2012
Trêss fatos cientÌficos associados à física de altas energias foram intensamente divulgados e discutidos ao longo de 2012: a) o vexame do experimento Opera; b) a descoberta de uma nova partícula pelo LHC, provavelmente o bóson de Higgs; c) a observação de uma linha espectral por volta de 130GeV, em meio aos dados coletados pelo telescópio Fermi desde 2008, e sua possível relação com matÈria escura. Esses fatos merecem o esforÁo de uma an·lise crÌtica para tirarmos algumas liÁıes. Acredito que algumas dessas lições podem servir para o nosso cotidiano de professores e pesquisadores
Entropy from Scaling Symmetry Breaking
The scaling symmetry in conformal quantum mechanics (CQM) can be broken due
to the boundary conditions that follow from the requirement of a unitary time
evolution of the Hamiltonian. We show that the scaling symmetry of CQM can be
restored by introducing a suitable mixed state, which is associated with a
nonvanishing von Neumann entropy. We give an explicit formula for the entropy
arising from the mixed state in CQM. Our work provides a direct link between
the restoration of a broken symmetry and von Neumann entropy.Comment: 13 page