2,099 research outputs found
Collapse models: from theoretical foundations to experimental verifications
The basic strategy underlying models of spontaneous wave function collapse
(collapse models) is to modify the Schroedinger equation by including nonlinear
stochastic terms, which tend to localize wave functions in space in a dynamical
manner. These terms have negligible effects on microscopic systems-therefore
their quantum behaviour is practically preserved. On the other end, since the
strength of these new terms scales with the mass of the system, they become
dominant at the macroscopic level, making sure that wave functions of
macro-objects are always well-localized in space. We will review these basic
features. By changing the dynamics of quantum systems, collapse models make
predictions, which are different from standard quantum mechanical predictions.
Although they are difficult to detect, we discuss the most relevant scenarios,
where such deviations can be observedComment: 10 Pages. Invited Talk at the Heinz von Foerster Centenary
International Conference on Self-Organization and Emergence: Emergent Quantum
Mechanics (EmerQuM11). Nov. 10-13, 2011, Vienna, Austria. Proceedings to
appear in J. Phys. (Conf. Series
The noncavitating performance and life of a small vane-type positive displacement pump in liquid hydrogen
The low flow rate and high head rise requirements of hydrogen/oxygen auxiliary propulsion systems make the application of centrifugal pumps difficult. Positive displacement pumps are well-suited for these flow conditions, but little is known about their performance and life characteristics in liquid hydrogen. An experimental and analytical investigation was conducted to determine the performance and life characteristics of a vane-type, positive displacement pump. In the experimental part of this effort, mass flow rate and shaft torque were determined as functions of shaft speed and pump pressure rise. Since liquid hydrogen offers little lubrication in a rubbing situation, pump life is an issue. During the life test, the pump was operated intermittently for 10 hr at the steady-state point of 0.074 lbm/sec (0.03 kg/sec) flow rate, 3000 psid (2.07 MPa) pressure rise, and 8000 rpm (838 rad/sec) shaft speed. Pump performance was monitored during the life test series and the results indicated no loss in performance. Material loss from the vanes was recorded and wear of the other components was documented. In the analytical part of this effort, a comprehensive pump performance analysis computer code, developed in-house, was used to predict pump performance. The results of the experimental investigation are presented and compared with the results of the analysis. Results of the life test are also presented
Non-interferometric Test of Collapse Models in Optomechanical Systems
The test of modifications to quantum mechanics aimed at identifying the
fundamental reasons behind the un-observability of quantum mechanical
superpositions at the macro-scale is a crucial goal of modern quantum
mechanics. Within the context of collapse models, current proposals based on
interferometric techniques for their falsification are far from the
experimental state-of-the-art. Here we discuss an alternative approach to the
testing of quantum collapse models that, by bypassing the need for the
preparation of quantum superposition states might help us addressing non-linear
stochastic mechanisms such as the one at the basis of the continuous
spontaneous localisation model.Comment: 6 pages, accepted for publication in Phys. Rev. Lett.
Testing collapse models with levitated nanoparticles: the detection challenge
We consider a nanoparticle levitated in a Paul trap in ultrahigh cryogenic
vacuum, and look for the conditions which allow for a stringent
noninterferometric test of spontaneous collapse models. In particular we
compare different possible techniques to detect the particle motion. Key
conditions which need to be achieved are extremely low residual pressure and
the ability to detect the particle at ultralow power. We compare three
different detection approaches based respectively on a optical cavity, optical
tweezer and a electrical readout, and for each one we assess advantages,
drawbacks and technical challenges
Color-charge separation in trapped SU(3) fermionic atoms
Cold fermionic atoms with three different hyperfine states with
SU(3) symmetry confined in one-dimensional optical lattices show color-charge
separation, generalizing the conventional spin charge separation for
interacting SU(2) fermions in one dimension. Through time-dependent DMRG
simulations, we explore the features of this phenomenon for a generalized SU(3)
Hubbard Hamiltonian. In our numerical simulations of finite size systems, we
observe different velocities of the charge and color degrees of freedom when a
Gaussian wave packet or a charge (color) density response to a local
perturbation is evolved. The differences between attractive and repulsive
interactions are explored and we note that neither a small anisotropy of the
interaction, breaking the SU(3) symmetry, nor the filling impedes the basic
observation of these effects
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Queer to be kind: Exploring Western media discourses about the “Eastern bloc” during the 2007 and 2014 Eurovision Song Contests
This article examines the voting results and Western European media coverage of the 2007 and 2014 Eurovision Song Contests. The Austrian drag act Conchita Wurst (the alter ego of an openly gay man) won in 2014, whilst Serbian entrant Marija Šerifović, portrayed in Western European media as lesbian at the time, won in 2007. We first explore the extent to which there was an East-West voting divide in both contests. In 2014, while there was some elite hostility against Conchita in Eastern Europe, the popular support was on a similar level to that in Western Europe. In 2007, we find no significant geographic divide in support for Šerifović. However, when we examine mainstream UK and German media coverage during and after both contests, we find strong anti-Eastern European discourses that are at odds with the similarity in the public voting. We employ the concept of homonationalism to interrogate inconsistent Western media discourses: the East was depicted as a site of homophobia and the West as a site of tolerance in 2014, whilst the queer aesthetic/identity of Šerifović was largely overlooked in 2007
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