Simplifying collaboration in co-located virtual environments using the active-passive approach

The design and implementation of co-located immersive virtual environments with equal interaction possibilities for all participants is a complex topic. The main problem, on a fundamental technical level, is the difficulty of providing perspective-correct images for each participant. There is consensus that the lack of a correct perspective view will negatively affect interaction fidelity and therefore also collaboration. Several research approaches focus on providing a correct perspective view to all participants to enable co-located work. However, these approaches are usually either based on custom hardware solutions that limit the number of users with a correct perspective view or software solutions striving to eliminate or mitigate restrictions with custom image-generation approaches. In this paper we investigate an often overlooked approach to enable collaboration for multiple users in an immersive virtual environment designed for a single user. The approach provides one (active) user with a perspective-correct view while other (passive) users receive visual cues that are not perspective-correct. We used this active-passive approach to investigate the limitations posed by assigning the viewpoint to only one user. The findings of our study, though inconclusive, revealed two curiosities. First, our results suggest that the location of target geometry is an important factor to consider for designing interaction, expanding on prior work that has studied only the relation between user positions. Secondly, there seems to be only a low cost involved in accepting the limitation of providing perspective-correct images to a single user, when comparing with a baseline, during a coordinated work approach. These findings advance our understanding of collaboration in co-located virtual environments and suggest an approach to simplify co-located collaboration

Fuzzy Self-Learning Controllers for Elasticity Management in Dynamic Cloud Architectures

Cloud controllers support the operation and quality management of dynamic cloud architectures by automatically scaling the compute resources to meet performance guarantees and minimize resource costs. Existing cloud controllers often resort to scaling strategies that are codified as a set of architecture adaptation rules. However, for a cloud provider, deployed application architectures are black-boxes, making it difficult at design time to define optimal or pre-emptive adaptation rules. Thus, the burden of taking adaptation decisions often is delegated to the cloud application. We propose the dynamic learning of adaptation rules for deployed application architectures in the cloud. We introduce FQL4KE, a self-learning fuzzy controller that learns and modifies fuzzy rules at runtime. The benefit is that we do not have to rely solely on precise design-time knowledge, which may be difficult to acquire. FQL4KE empowers users to configure cloud controllers by simply adjusting weights representing priorities for architecture quality instead of defining complex rules. FQL4KE has been experimentally validated using the cloud application framework ElasticBench in Azure and OpenStack. The experimental results demonstrate that FQL4KE outperforms both a fuzzy controller without learning and the native Azure auto-scalin

Illuminating the 1/x moment of parton distribution functions

The Weisberger relation, an exact statement of the parton model, elegantly relates a high-energy physics observable, the 1/x moment of parton distribution functions, to a nonperturbative low-energy observable: the dependence of the nucleon mass on the value of the quark mass or its corresponding quark condensate. We show that contemporary fits to nucleon structure functions fail to determine this 1/x moment; however, deeply virtual Compton scattering can be described in terms of a novel F_{1/x}(t) form factor which illuminates this physics. An analysis of exclusive photon-induced processes in terms of the parton-nucleon scattering amplitude with Regge behavior reveals a failure of the high Q^2 factorization of exclusive processes at low t in terms of the Generalized Parton-Distribution Functions which has been widely believed to hold in the past. We emphasize the need for more data for the DVCS process at large t in future or upgraded facilities.Comment: 11 pages, 3 figures, invited contribution to the 11th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon, sept. 10th-14th 2007, Juelich, German

Probing the infrared quark mass from highly excited baryons

We argue that three-quark excited states naturally group into quartets, split into two parity doublets, and that the mass splittings between these parity partners decrease higher up in the baryon spectrum. This decreasing mass difference can be used to probe the running quark mass in the mid-infrared power-law regime. A measurement of masses of high-partial wave Delta* resonances should be sufficient to unambiguously establish the approximate degeneracy. We test this concept with the first computation of excited high-j baryon masses in a chirally invariant quark model.Comment: 4 pages, 4 figures. submitted to Phys Rev Letter

Using highly excited baryons to catch the quark mass

Chiral symmetry in QCD can be simultaneously in Wigner and Goldstone modes, depending on the part of the spectrum examined. The transition regime between both, exploiting for example the onset of parity doubling in the high baryon spectrum, can be used to probe the running quark mass in the mid-IR power-law regime. In passing we also argue that three-quark states naturally group into same-flavor quartets, split into two parity doublets, all splittings decreasing high in the spectrum. We propose that a measurement of masses of high-partial wave Delta* resonances should be sufficient to unambiguously establish the approximate degeneracy and see the quark mass running. We test these concepts with the first computation of the spectrum of high-J excited baryons in a chiral-invariant quark model.Comment: 6 pages, 9 figures, To appear in the proceedings of the 19th International IUPAP Conference on Few-Body Problems in Physics; added acknowledgment, hyphenized author nam

The BES f_0(1810): a new glueball candidate

We analyze the f_0(1810) state recently observed by the BES collaboration via radiative J/\psi decay to a resonant \phi\omega spectrum and confront it with DM2 data and glueball theory. The DM2 group only measured \omega\omega decays and reported a pseudoscalar but no scalar resonance in this mass region. A rescattering mechanism from the open flavored KKbar decay channel is considered to explain why the resonance is only seen in the flavor asymmetric \omega\phi branch along with a discussion of positive C parity charmonia decays to strengthen the case for preferred open flavor glueball decays. We also calculate the total glueball decay width to be roughly 100 MeV, in agreement with the narrow, newly found f_0, and smaller than the expected estimate of 200-400 MeV. We conclude that this discovered scalar hadron is a solid glueball candidate and deserves further experimental investigation, especially in the K-Kbar channel. Finally we comment on other, but less likely, possible assignments for this state.Comment: 11 pages, 4 figures. Major substantive additions, including an ab-initio, QCD-based computation of the glueball inclusive decay width, evaluation of final state effects, and enhanced discussion of several alternative possibilities. Our conclusions are unchanged: the BES f_0(1810) is a promising glueball candidat

Chirally symmetric quark description of low energy \pi-\pi scattering

Weinberg's theorem for \pi-\pi scattering, including the Adler zero at threshold in the chiral limit, is analytically proved for microscopic quark models that preserve chiral symmetry. Implementing Ward-Takahashi identities, the isospin 0 and 2 scattering lengths are derived in exact agreement with Weinberg's low energy results. Our proof applies to alternative quark formulations including the Hamiltonian and Euclidean space Dyson-Schwinger approaches. Finally, the threshold \pi-\pi scattering amplitudes are calculated using the Dyson-Schwinger equations in the rainbow-ladder truncation, confirming the formal derivation.Comment: 10 pages, 7 figures, Revtex

NASA-JSC antenna near-field measurement system

Work was completed on the near-field range control software. The capabilities of the data processing software were expanded with the addition of probe compensation. In addition, the user can process the measured data from the same computer terminal used for range control. The design of the laser metrology system was completed. It provides precise measruement of probe location during near-field measurements as well as position data for control of the translation beam and probe cart. A near-field range measurement system was designed, fabricated, and tested

Chiral Symmetry and Hyperfine Quark-Antiquark Splittings

We briefly review theoretical calculations for the pseudoscalar-vector meson hyperfine splitting with no open flavor and also report a many body field theoretical effort to assess the impact of chiral symmetry in the choice of effective potentials for relativistic quark models. Our calculations predict the missing eta_b meson to have mass near 9400 $MeV$. The radial excitation $\eta_c(2S)$ is in agreement with the measurements of the BELLE and most recently BABAR collaborations.Comment: European HEP conference proceedings (Aachen, July 2003). A few typographical errors correcte