Decoherence of Macroscopic Closed Systems within Newtonian Quantum Gravity

A theory recently proposed by the author aims to explain decoherence and the thermodynamical behaviour of closed systems within a conservative, unitary, framework for quantum gravity by assuming that the operators tied to the gravitational degrees of freedom are unobservable and equating physical entropy with matter-gravity entanglement entropy. Here we obtain preliminary results on the extent of decoherence this theory predicts. We treat first a static state which, if one were to ignore quantum gravitational effects, would be a quantum superposition of two spatially displaced states of a single classically well describable ball of uniform mass density in empty space. Estimating the quantum gravitational effects on this system within a simple Newtonian approximation, we obtain formulae which predict e.g. that as long as the mass of the ball is considerably larger than the Planck mass, such a would-be-coherent static superposition will actually be decohered whenever the separation of the centres of mass of the two ball-states excedes a small fraction (which decreases as the mass of the ball increases) of the ball radius. We then obtain a formula for the quantum gravitational correction to the would-be-pure density matrix of a non-relativistic many-body Schroedinger wave function and argue that this formula predicts decoherence between configurations which differ (at least) in the "relocation" of a cluster of particles of Planck mass. We estimate the entropy of some simple model closed systems, finding a tendency for it to increase with "matter-clumping" suggestive of a link with existing phenomenological discussions of cosmological entropy increase.Comment: 11 pages, plain TeX, no figures. Accepted for publication as a "Letter to the Editor" in "Classical and Quantum Gravity

Global atmospheric moisture variability

Research efforts during FY-88 have focused on completion of several projects relating to analysis of FGGE data during SOP-1 and on expanded studies of global atmospheric moisture. In particular, a revised paper on the relationship between diabatic heating and baroclinicity in the South Pacific Convergence Zone (SPCZ) was submitted. A summary of completed studies on diagnostic convective parameterization was presented at the Satellite Meteorology and Oceanography Convergence last February. These investigations of diabatic heating in the SPCZ have demonstrated the requirement for a more quantitative description of atmospheric moisture. As a result, efforts were directed toward use of passive remote microwave measurements from the Nimbus-7 SMMR and the DOD's Special Sensor Microwave Imager (SSMI/I) as critical sources of moisture data. Activities this year are summarized

The effect of radiative cooling on scaling laws of X-ray groups and clusters

We have performed cosmological simulations in a ΛCDM cosmology with and without radiative cooling in order to study the effect of cooling on the cluster scaling laws. Our simulations consist of 4.1 million particles each of gas and dark matter within a box size of 100 h-1 Mpc, and the run with cooling is the largest of its kind to have been evolved to z = 0. Our cluster catalogs both consist of over 400 objects and are complete in mass down to ~1013 h-1 M☉. We contrast the emission-weighted temperature-mass (Tew-M) and bolometric luminosity-temperature (Lbol-Tew) relations for the simulations at z = 0. We find that radiative cooling increases the temperature of intracluster gas and decreases its total luminosity, in agreement with the results of Pearce et al. Furthermore, the temperature dependence of these effects flattens the slope of the Tew-M relation and steepens the slope of the Lbol-Tew relation. Inclusion of radiative cooling in the simulations is sufficient to reproduce the observed X-ray scaling relations without requiring excessive nongravitational energy injection

Improved detection of small atom numbers through image processing

We demonstrate improved detection of small trapped atomic ensembles through advanced post-processing and optimal analysis of absorption images. A fringe removal algorithm reduces imaging noise to the fundamental photon-shot-noise level and proves beneficial even in the absence of fringes. A maximum-likelihood estimator is then derived for optimal atom-number estimation and is applied to real experimental data to measure the population differences and intrinsic atom shot-noise between spatially separated ensembles each comprising between 10 and 2000 atoms. The combined techniques improve our signal-to-noise by a factor of 3, to a minimum resolvable population difference of 17 atoms, close to our ultimate detection limit.Comment: 4 pages, 3 figure

Quantum state transfer in spin chains with q-deformed interaction terms

We study the time evolution of a single spin excitation state in certain linear spin chains, as a model for quantum communication. Some years ago it was discovered that when the spin chain data (the nearest neighbour interaction strengths and the magnetic field strengths) are related to the Jacobi matrix entries of Krawtchouk polynomials or dual Hahn polynomials, so-called perfect state transfer takes place. The extension of these ideas to other types of discrete orthogonal polynomials did not lead to new models with perfect state transfer, but did allow more insight in the general computation of the correlation function. In the present paper, we extend the study to discrete orthogonal polynomials of q-hypergeometric type. A remarkable result is a new analytic model where perfect state transfer is achieved: this is when the spin chain data are related to the Jacobi matrix of q-Krawtchouk polynomials. The other cases studied here (affine q-Krawtchouk polynomials, quantum q-Krawtchouk polynomials, dual q-Krawtchouk polynomials, q-Hahn polynomials, dual q-Hahn polynomials and q-Racah polynomials) do not give rise to models with perfect state transfer. However, the computation of the correlation function itself is quite interesting, leading to advanced q-series manipulations

Quantum Chinos Game: winning strategies through quantum fluctuations

We apply several quantization schemes to simple versions of the Chinos game. Classically, for two players with one coin each, there is a symmetric stable strategy that allows each player to win half of the times on average. A partial quantization of the game (semiclassical) allows us to find a winning strategy for the second player, but it is unstable w.r.t. the classical strategy. However, in a fully quantum version of the game we find a winning strategy for the first player that is optimal: the symmetric classical situation is broken at the quantum level.Comment: REVTEX4.b4 file, 3 table

Semiclassical time--dependent propagation in three dimensions: How accurate is it for a Coulomb potential?

A unified semiclassical time propagator is used to calculate the semiclassical time-correlation function in three cartesian dimensions for a particle moving in an attractive Coulomb potential. It is demonstrated that under these conditions the singularity of the potential does not cause any difficulties and the Coulomb interaction can be treated as any other non-singular potential. Moreover, by virtue of our three-dimensional calculation, we can explain the discrepancies between previous semiclassical and quantum results obtained for the one-dimensional radial Coulomb problem.Comment: 8 pages, 4 figures (EPS

Generating quantum states through spin chain dynamics

Spin chains can realise perfect quantum state transfer between the two ends via judicious choice of coupling strengths. In this paper, we study what other states can be created by engineering a spin chain. We conclude that, up to local phases, all single excitation quantum states with support on every site of the chain can be created. We pay particular attention to the generation of W-states that are superposed over every site of the chain.Comment: 9 pages, 1 figur

Nature versus Nurture: The curved spine of the galaxy cluster X-ray luminosity -- temperature relation

The physical processes that define the spine of the galaxy cluster X-ray luminosity -- temperature (L-T) relation are investigated using a large hydrodynamical simulation of the Universe. This simulation models the same volume and phases as the Millennium Simulation and has a linear extent of 500 h^{-1} Mpc. We demonstrate that mergers typically boost a cluster along but also slightly below the L-T relation. Due to this boost we expect that all of the very brightest clusters will be near the peak of a merger. Objects from near the top of the L-T relation tend to have assembled much of their mass earlier than an average halo of similar final mass. Conversely, objects from the bottom of the relation are often experiencing an ongoing or recent merger.Comment: 8 pages, 7 figures, submitted to MNRA

The basicranial anatomy of African Eocene-Oligocene anthropoids : Are there any clues for platyrrhine origins?

A contentious issue in anthropoid evolution is clarifying the phylogenetic position of late Eocene and early Oligocene anthropoids from Egypt relative to Miocene-to-recent "crown" Anthropoidea. There is general agreement that African early Oligocene Aegyptopithecus and other Propliopithecidae are members of a stem catarrhine clade but do any of the other African Eocene-Oligocene anthropoids represent stem platyrrhines? Related to this, do any of the late Eocene taxa, such as the Oligopithecidae (Catopithecus and Oligopithecus), also represent stem catarrrhines, or are they stem anthropoids with a few characters convergent on the catarrhine condition? The distribution of traits of the ear regions of living and fossil anthropoids is examined using CT scans of the temporal regions of a comparative sample of extant haplorhines as well as the Egyptian late Eocene Catopithecus and Proteopithecus and early Oligocene taxa Simonsius, Apidium, and Aegyptopithecus to determine if there are any characters of the ear region that distinguish crown platyrrhines from crown catarrhines and if any represent synapomorphies of Platyrrhini and thereby indicating that some late Eocene African taxa are sister to platyrrhine primates. The ear region of African anthropoids is essentially modern in form by the late Eocene (~35 Ma) and has undergone only a few and minor structural changes since. Overall, the few structural details of the ear region that separate Miocene to recent platyrrhines from crown catarrhines represent catarrhine synapomorphies. Several of these synapomorphies support linkage between early Oligocene Aegyptopithecus and crown catarrhines. In particular, failure to ossify the tentorium cerebelli and less certainly, reduction of Cartmill's canal and its constituent vein may be catarrhines synapomorpies. Miocene to recent platyrrhines are very similar to late Eocene African anthropoids in the anatomy of the arteries and veins, the design of the tympanic cavity, its accessory pneumatic sinuses, and the structure and relations of the tympanic bone. Proteopithecus remains a possible platyrrhine ancestor but only because of shared primitive retentions from a more distant common ancestor.Sesiones libresFacultad de Ciencias Naturales y Muse