Massless particles, electromagnetism, and Rieffel induction

The connection between space-time covariant representations (obtained by inducing from the Lorentz group) and irreducible unitary representations (induced from Wigner's little group) of the Poincar\'{e} group is re-examined in the massless case. In the situation relevant to physics, it is found that these are related by Marsden-Weinstein reduction with respect to a gauge group. An analogous phenomenon is observed for classical massless relativistic particles. This symplectic reduction procedure can be (`second') quantized using a generalization of the Rieffel induction technique in operator algebra theory, which is carried through in detail for electro- magnetism. Starting from the so-called Fermi representation of the field algebra generated by the free abelian gauge field, we construct a new (`rigged') sesquilinear form on the representation space, which is positive semi-definite, and given in terms of a Gaussian weak distribution (promeasure) on the gauge group (taken to be a Hilbert Lie group). This eventually constructs the algebra of observables of quantum electro- magnetism (directly in its vacuum representation) as a representation of the so-called algebra of weak observables induced by the trivial representation of the gauge group.Comment: LaTeX, 52 page

An Inconsistency in the Simulation of Bose-Einstein Correlations

We show that the formalism commonly used to implement Bose-Einstein correlations in Monte-Carlo simulations can lead to values of the two-particle correlator significantly smaller than unity, in the case of sources with strong position-momentum correlations. This is more pronounced when the phase space of the emitted particles is strongly reduced by experimental acceptance or kinematic analysis selections. It is inconsistent with general principles according to which the Bose-Einstein correlator is larger than unity. This inconsistency seems to be rooted in the fact that quantum mechanical localization properties are not taken into account properly.Comment: 10 pages, LaTe

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 Stückelberg-Kibble model as an example of quantized symplectic reduction

Recently, it has been observed that a certain class of classical theories with constraints can be quantized by a mathematical procedure known as Rieffel induction. After a short exposition of this idea, we apply the new quantization theory to the Stueckelberg-Kibble model. We explicitly construct the physical state space {\cal H}_{phys}, which carries a massive representation of the Poincar\'e group. The longitudinal one-particle component arises from a particular Bogoliubov transformation of the five (unphysical) degrees of freedom one has started with. Our discussion exhibits the particular features of the proposed constrained quantization theory in great clarity

Low-pT Collective Flow Induces High-pT Jet Quenching

Data on low-pT hadronic spectra are widely regarded as evidence of a hydrodynamic expansion in nucleus-nucleus collisions. In this interpretation, different hadron species emerge from a common medium that has built up a strong collective velocity field. Here, we show that the existence of a collective flow field implies characteristic modifications of high-pT parton fragmentation. We generalize the formalism of parton energy loss to the case of flow-induced, oriented momentum transfer. We also discuss how to embed this calculation in hydrodynamic simulations. Flow effects are found to result generically in characteristic asymmetries in the eta-phi-plane of jet energy distributions and of multiplicity distributions associated to high-pT trigger particles. But collective flow also contributes to the medium-induced suppression of single inclusive high-pT hadron spectra. In particular, we find that low-pT elliptic flow can induce a sizeable additional contribution to the high-pT azimuthal asymmetry by selective elimination of those hard partons which propagate with significant inclination against the flow field. This reduces at least partially the recently observed problem that models of parton energy loss tend to underpredict the large azimuthal asymmetry v2 of high-pT hadronic spectra in semi-peripheral Au+Au collisions.Comment: 26 pages LaTeX, 11 eps-figure