Two New Bounds on the Random-Edge Simplex Algorithm

We prove that the Random-Edge simplex algorithm requires an expected number of at most 13n/sqrt(d) pivot steps on any simple d-polytope with n vertices. This is the first nontrivial upper bound for general polytopes. We also describe a refined analysis that potentially yields much better bounds for specific classes of polytopes. As one application, we show that for combinatorial d-cubes, the trivial upper bound of 2^d on the performance of Random-Edge can asymptotically be improved by any desired polynomial factor in d.Comment: 10 page

High pT leading hadron suppression in nuclear collisions at sqrt(s_NN) = 20 -- 200 GeV: data versus parton energy loss models

Experimental results on high transverse momentum (leading) hadron spectra in nucleus-nucleus collisions in the range sqrt(s_NN) = 20 -- 200 GeV are reviewed with an emphasis on the observed suppression compared to free space production in proton-proton collisions at the corresponding center-of-mass energies. The transverse-momentum and collision-energy (but seemingly not the in-medium path length) dependence of the experimental suppression factors measured in central collisions is consistent with the expectations of final-state non-Abelian parton energy loss in a dense QCD medium.Comment: Two typos correcte

Universal Pion Freeze-out Phase-Space Density

Results on the pion freeze-out phase-space density in sulphur-nucleus, Pb-Pb and pion-proton collisions at CERN-SPS are presented. All heavy-ion reactions are consistent with the thermal Bose-Einstein distrtibution f=1/(exp(E/T)-1) at T~120 MeV, modified for expansion. Pion-proton data are also consistent with f, but at T~180 MeV.Comment: 1 page, 1 figure; 98' report for GSI-Darmstad

Virtual Reality 3rd person camera behavior modes

We describe and evaluate five different level design independent modes of handling camera behavior in the 3rd person game LizzE – And the Light of Dreams in Virtual Reality. The behavior of the different modes will each be illustrated in detail. To evaluate the modes A: Fast circling, B: Lazy Circling, C: No Circling, D: Blink circling and E: Buffered pulling, an experimental study with 33 subjects was conducted. An analysis of the resulting data will show why Buffered pulling seems to be the most promising of the examined modes. We elaborate on the quantitative and qualitative hybrid experiment design and methodology. Eventually the advantages and disadvantages of the five tested modes are discussed in terms of supporting the gameplay, player enjoyment, in game performance and the tendency to induce nausea

An experiment design: investigating VR locomotion & virtual object interaction mechanics

In this paper, we describe an experiment outline on investigating design and user experience related aspects of several virtual reality locomotion and virtual object interaction mechanics. These mechanics will be based on consumer hardware like a common game controllers, an infrared hand and finger tracking device, VR hand controllers and an omnidirectional treadmill. Corresponding related work will contextualize and motivate this research. The projected experimental study will be based on user test sessions with a specifically developed 1st person VR puzzle horror game, called Gooze. A hybrid approach of self-assessment, in-game parameter tracking and session observations will be proposed for the investigation. Statistical analysis methods will be suggested to evaluate results. Furthermore, this paper will give an overview of the game and elaborate on design, gameplay and user experience related insights of already conducted informal pre-studies with it

Local multiplayer immersion affected by 3D stereoscopy

In this paper, we describe an experimental study, which evaluates how 3D stereoscopy affects player immersion in a possibly very distracting local multiplayer game. The game “Nicely Dicely” was specifically developed for this purpose, with 3D stereoscopy in mind, right from the beginning. Groups of participants were competitively playing the game in non-3D monoscopic and 3D stereoscopic presentations via a 3D compatible projector and corresponding active shutter glasses. In the following, we elaborate on the game and our quantitative and qualitative hybrid experiment design and methodology. An analysis of the resulting data will show that, indeed 3D stereoscopy significantly increases spatial presence, involvement and player immersion, even in a local multiplayer situation. Furthermore, some guiding insights relating the game’s design will be illustrated

UX evaluation of VR locomotion & virtual object interaction mechanics

Virtual Reality (VR) Interactions like in Ready Player One? Locomotion (LOC) and Virtual Object Interaction (VOI) are two key areas of concern, when designing and developing VR games and other VR applications. This paper describes a study of three interaction modes and their underlying VOI and LOC mechanics, using a range of consumer-oriented VR input setups, spanning from gamepad, over Spatially Tracked Hand Controllers, to Controllerless Hand Tracking and Omnidirectional Treadmill. All corresponding mechanics were implemented in the specifically developed, optimized and polished “real-world” game Gooze, to test them in a real-world scenario with corresponding challenges in gaming and human computer interaction. A within-subjects experiment with 89 participants using qualitative and quantitative analysis methods was conducted. The interaction modes and their mechanics were evaluated based on the four User Experience aspects: Player Enjoyment, Support of Gameplay, Simulator Sickness and Presence, with the latter being subdivided into the four sub-parameters: General Presence, Spatial Presence, Involvement and Experienced Realism, according to the igroup Presence Questionnaire. The paper concludes with summarizing the individual advantages and disadvantages of the assessed interaction modes

“VRification”: applying virtual reality to digital games

In the following, we discuss the process of applying virtual reality to digital games. We named this process “VRification” and will elaborate on some of its opportunities and issues. Based on a literature survey and professional practice, this work covers several examples of VR games, which were intended as such from the beginning (Job Simulator and Lucky’s Tale) and others, which were ported to VR after their initial release (DOOM VR and LizzE). We conclude that, for VR games, it is essential to be optimized for the full potential of targeted interface technologies. Furthermore, porting former-non-VR games to VR can create successful user experiences, when aiming for the same high standard of optimization, especially regarding simulator sickness

The complex environment of the bright carbon star TX Psc as probed by spectro-astrometry

Context: Stars on the asymptotic giant branch (AGB) show broad evidence of inhomogeneous atmospheres and circumstellar envelopes. These have been studied by a variety of methods on various angular scales. In this paper we explore the envelope of the well-studied carbon star TX Psc by the technique of spectro-astrometry. Aims: We explore the potential of this method for detecting asymmetries around AGB stars. Methods:We obtained CRIRES observations of several CO $\Delta$v=1 lines near 4.6 $\mu$m and HCN lines near 3 $\mu$m in 2010 and 2013. These were then searched for spectro-astrometric signatures. For the interpretation of the results, we used simple simulated observations. Results: Several lines show significant photocentre shifts with a clear dependence on position angle. In all cases, tilde-shaped signatures are found where the positive and negative shifts (at PA 0deg) are associated with blue and weaker red components of the lines. The shifts can be modelled with a bright blob 70 mas to 210 mas south of the star with a flux of several percent of the photospheric flux. We estimate a lower limit of the blob temperature of 1000 K. The blob may be related to a mass ejection as found for AGB stars or red supergiants. We also consider the scenario of a companion object. Conclusions: Although there is clear spectro-astrometric evidence of a rather prominent structure near TX Psc, it does not seem to relate to the other evidence of asymmetries, so no definite explanation can be given. Our data thus underline the very complex structure of the environment of this star, but further observations that sample the angular scales out to a few hundred milli-arcseconds are needed to get a clearer picture