12,709 research outputs found
The responses of people to virtual humans in an immersive virtual environment
This paper presents an experiment investigating the impact of behavior and responsiveness
on social responses to virtual humans in an immersive virtual environment
(IVE). A number of responses are investigated, including presence, copresence, and
two physiological responses—heart rate and electrodermal activity (EDA). Our
findings suggest that increasing agents’ responsiveness even on a simple level can
have a significant impact on certain aspects of people’s social responses to humanoid
agents.
Despite being aware that the agents were computer-generated, participants with
higher levels of social anxiety were significantly more likely to avoid “disturbing”
them. This suggests that on some level people can respond to virtual humans as
social actors even in the absence of complex interaction.
Responses appear to be shaped both by the agents’ behaviors and by people’s expectations
of the technology. Participants experienced a significantly higher sense of
personal contact when the agents were visually responsive to them, as opposed to
static or simply moving. However, this effect diminished with experienced computer
users. Our preliminary analysis of objective heart-rate data reveals an identical pattern
of responses
Spin state transition in LaCoO3 by variational cluster approximation
The variational cluster approximation is applied to the calculation of
thermodynamical quantities and single-particle spectra of LaCoO3. Trial
self-energies and the numerical value of the Luttinger-Ward functional are
obtained by exact diagonalization of a CoO6 cluster. The VCA correctly predicts
LaCoO3 as a paramagnetic insulator and a gradual and relatively smooth increase
of the occupation of high-spin Co3+ ions causes the temperature dependence of
entropy and magnetic susceptibility. The single particle spectral function
agrees well with experiment, the experimentally observed temperature dependence
of photoelectron spectra is reproduced satisfactorily. Remaining discrepancies
with experiment highlight the importance of spin orbit coupling and local
lattice relaxation.Comment: Revtex file with 10 eps figure
Correlated band structure of NiO, CoO and MnO by variational cluster approximation
The variational cluster approximation proposed by Potthoff is applied to the
calculation of the single-particle spectral function of the transition metal
oxides MnO, CoO and NiO. Trial self-energies and the numerical value of the
Luttinger-Ward functional are obtained by exact diagonalization of a
TMO6-cluster. The single-particle parameters of this cluster serve as
variational parameters to construct a stationary point of the grand potential
of the lattice system. The stationary point is found by a crossover procedure
which allows to go continuously from an array of disconnected clusters to the
lattice system. The self-energy is found to contain irrelevant degrees of
freedom which have marginal impact on the grand potential and which need to be
excluded to obtain meaningful results. The obtained spectral functions are in
good agreement with experimental data.Comment: 14 pages, 17 figure
A priori probability that a qubit-qutrit pair is separable
We extend to arbitrarily coupled pairs of qubits (two-state quantum systems)
and qutrits (three-state quantum systems) our earlier study (quant-ph/0207181),
which was concerned with the simplest instance of entangled quantum systems,
pairs of qubits. As in that analysis -- again on the basis of numerical
(quasi-Monte Carlo) integration results, but now in a still higher-dimensional
space (35-d vs. 15-d) -- we examine a conjecture that the Bures/SD (statistical
distinguishability) probability that arbitrarily paired qubits and qutrits are
separable (unentangled) has a simple exact value, u/(v Pi^3)= >.00124706, where
u = 2^20 3^3 5 7 and v = 19 23 29 31 37 41 43 (the product of consecutive
primes). This is considerably less than the conjectured value of the Bures/SD
probability, 8/(11 Pi^2) = 0736881, in the qubit-qubit case. Both of these
conjectures, in turn, rely upon ones to the effect that the SD volumes of
separable states assume certain remarkable forms, involving "primorial"
numbers. We also estimate the SD area of the boundary of separable qubit-qutrit
states, and provide preliminary calculations of the Bures/SD probability of
separability in the general qubit-qubit-qubit and qutrit-qutrit cases.Comment: 9 pages, 3 figures, 2 tables, LaTeX, we utilize recent exact
computations of Sommers and Zyczkowski (quant-ph/0304041) of "the Bures
volume of mixed quantum states" to refine our conjecture
Bures distance between two displaced thermal states
The Bures distance between two displaced thermal states and the corresponding
geometric quantities (statistical metric, volume element, scalar curvature) are
computed. Under nonunitary (dissipative) dynamics, the statistical distance
shows the same general features previously reported in the literature by
Braunstein and Milburn for two--state systems. The scalar curvature turns out
to have new interesting properties when compared to the curvature associated
with squeezed thermal states.Comment: 3 pages, RevTeX, no figure
Cortical pain responses in human infants
Despite the recent increase in our understanding of the development of pain processing, it is still not known whether premature infants are capable of processing pain at a cortical level. In this study, changes in cerebral oxygenation over the somatosensory cortex were measured in response to noxious stimulation using real-time near-infrared spectroscopy in 18 infants aged between 25 and 45 weeks postmenstrual age. The noxious stimuli were heel lances performed for routine blood sampling; no blood tests were performed solely for the purpose of the study. Noxious stimulation produced a clear cortical response, measured as an increase in total hemoglobin concentration [HbT] in the contralateral somatosensory cortex, from 25 weeks (mean Delta[HbT] = 7.74 mu mol/L; SE, 1.10). Cortical responses were significantly greater in awake compared with sleeping infants, with a mean difference of 6.63 mu mol/L [95% confidence interval (CI) limits: 2.35, 10.91 mu mol/L; mean age, 35.2 weeks]. In awake infants, the response in the contralateral somatosensory cortex increased with age ( regression coefficient, 0.698 mu mol/L/week; 95% CI limits: 0.132, 1.265 mu mol/L/week) and the latency decreased with age (regression coefficient, -0.9861 mu mol/L/week; 95% CI limits: -1.5361, -0.4361 mu mol/L/week; age range, 25-38 weeks). The response was modality specific because no response was detected after non-noxious stimulation of the heel, even when accompanied by reflex withdrawal of the foot. We conclude that noxious information is transmitted to the preterm infant cortex from 25 weeks, highlighting the potential for both higher-level pain processing and pain-induced plasticity in the human brain from a very early age
High-Temperature Expansions of Bures and Fisher Information Priors
For certain infinite and finite-dimensional thermal systems, we obtain ---
incorporating quantum-theoretic considerations into Bayesian thermostatistical
investigations of Lavenda --- high-temperature expansions of priors over
inverse temperature beta induced by volume elements ("quantum Jeffreys' priors)
of Bures metrics. Similarly to Lavenda's results based on volume elements
(Jeffreys' priors) of (classical) Fisher information metrics, we find that in
the limit beta -> 0, the quantum-theoretic priors either conform to Jeffreys'
rule for variables over [0,infinity], by being proportional to 1/beta, or to
the Bayes-Laplace principle of insufficient reason, by being constant. Whether
a system adheres to one rule or to the other appears to depend upon its number
of degrees of freedom.Comment: Six pages, LaTeX. The title has been shortened (and then further
modified), at the suggestion of a colleague. Other minor change
From presence to consciousness through virtual reality
Immersive virtual environments can break the deep, everyday connection between where our senses tell us we are and where we are actually located and whom we are with. The concept of 'presence' refers to the phenomenon of behaving and feeling as if we are in the virtual world created by computer displays. In this article, we argue that presence is worthy of study by neuroscientists, and that it might aid the study of perception and consciousness
Microscopic thickness determination of thin graphite films formed on SiC from quantized oscillation in reflectivity of low-energy electrons
Low-energy electron microscopy (LEEM) was used to measure the reflectivity of
low-energy electrons from graphitized SiC(0001). The reflectivity shows
distinct quantized oscillations as a function of the electron energy and
graphite thickness. Conduction bands in thin graphite films form discrete
energy levels whose wave vectors are normal to the surface. Resonance of the
incident electrons with these quantized conduction band states enhances
electrons to transmit through the film into the SiC substrate, resulting in
dips in the reflectivity. The dip positions are well explained using
tight-binding and first-principles calculations. The graphite thickness
distribution can be determined microscopically from LEEM reflectivity
measurements.Comment: 7 pages, 3 figure
- …