35,103 research outputs found
A Realist Interpretation of the Quantum Measurement Problem
A new, realist interpretation of the quantum measurement processes is given.
In this scenario a quantum measurement is a non-equilibrium phase transition in
a ``resonant cavity'' formed by the entire physical universe including all its
material and energy content. Both the amplitude and the phase of the quantum
mechanical wavefunction acquire substantial meaning in this picture, and the
probabilistic element is removed from the foundations of quantum mechanics, its
apparent presence in the quantum measurement process is viewed as a result of
the sensitive dependence on initial/boundary conditions of the non-equilibrium
phase transitions in a many degree-of-freedom system. The implications of
adopting this realist ontology to the clarification and resolution of lingering
issues in the foundations of quantum mechanics, such as wave-particle duality,
Heisenberg's uncertainty relation, Schrodinger's Cat paradox, first and higher
order coherence of photons and atoms, virtual particles, the existence of
commutation relations and quantized behavior, etc., are also presented.Comment: 8 pages, submiited to the Proceedings of the international conference
"Albert Einstein Century", held July 2005 in Paris, Franc
Shock dynamics of phase diagrams
A thermodynamic phase transition denotes a drastic change of state of a physical system due to a continuous change of thermodynamic variables, as for instance pressure and temperature. The classical van der Waals equation of state is the simplest model that predicts the occurrence of a critical point associated with the gas-liquid phase transition. Nevertheless, below the critical temperature, theoretical predictions of the van der Waals theory significantly depart from the observed physical behaviour. We develop a novel approach to classical thermodynamics based on the solution of Maxwell relations for a generalised family of nonlocal entropy functions. This theory provides an exact mathematical description of discontinuities of the order parameter within the phase transition region, it explains the universal form of the equations of state and the occurrence of triple points in terms of the dynamics of nonlinear shock wave fronts
Strong-disorder magnetic quantum phase transitions: Status and new developments
This article reviews the unconventional effects of random disorder on
magnetic quantum phase transitions, focusing on a number of new experimental
and theoretical developments during the last three years. On the theory side,
we address smeared quantum phase transitions tuned by changing the chemical
composition, for example in alloys of the type AB. We also discuss
how the interplay of order parameter conservation and overdamped dynamics leads
to enhanced quantum Griffiths singularities in disordered metallic
ferromagnets. Finally, we discuss a semiclassical theory of transport
properties in quantum Griffiths phases. Experimental examples include the
ruthenates SrCaRuO and (SrCa)RuO as
well as Ba(FeMn)As.Comment: 9 pages, 2 figures, Proceedings of the International Conference on
Recent Progress in Many-Body Theories 17, final version as publishe
Critical behavior of a one-dimensional fixed-energy stochastic sandpile
We study a one-dimensional fixed-energy version (that is, with no input or
loss of particles), of Manna's stochastic sandpile model. The system has a
continuous transition to an absorbing state at a critical value of
the particle density. Critical exponents are obtained from extensive
simulations, which treat both stationary and transient properties. In contrast
with other one-dimensional sandpiles, the model appears to exhibit finite-size
scaling, though anomalies exist in the scaling of relaxation times and in the
approach to the stationary state. The latter appear to depend strongly on the
nature of the initial configuration. The critical exponents differ from those
expected at a linear interface depinning transition in a medium with point
disorder, and from those of directed percolation.Comment: 15 pages, 11 figure
Spectroscopy of soft modes and quantum phase transitions in coupled electron bilayers
Strongly-correlated two-dimensional electrons in coupled semiconductor
bilayers display remarkable broken symmetry many-body states under accessible
and controllable experimental conditions. In the cases of continuous quantum
phase transitions soft collective modes drive the transformations that link
distinct ground states of the electron double layers. In this paper we consider
results showing that resonant inelastic light scattering methods detect soft
collective modes of the double layers and probe their evolution with
temperature and magnetic field. The light scattering experiments offer venues
of research of fundamental interactions and continuous quantum phase
transitions in low-dimensional electron liquids.Comment: 10 pages, 7 figure
- …