Light like segment compactification and braneworlds with dynamical string tension

There is great interest in the construction of brane worlds, where matter and gravity are forced to be effective only in a lower dimensional surface, the brane . How these could appear as a consequence of string theory is a crucial question and this has been widely discussed. Here we will examine a distinct scenario that appears in dynamical string tension theories and where string tension is positive between two surfaces separated by a short distance and at the two surfaces themselves the string tensions become infinite, therefore producing an effective confinement of the strings and therefore of all matter and gravity to the space between these to surfaces, which is in fact a new type of stringy brane world scenario. The specific model studied is in the context of the modified measure formulation the string where tension appear as an additional dynamical degree of freedom and these tensions are not universal, but rather each string generates its own tension, which can have a different value for each string. We consider a new background field that can couple to these strings, the tension scalar is capable then of changing locally along the world sheet and then the value of the tension of the extended object changes accordingly. When many types of strings probing the same region of space are considered this tension scalar is constrained by the requirement of quantum conformal invariance. For the case of two types of strings probing the same region of space with different dynamically generated tensions, there are two different metrics, associated to the different strings, that have to satisfy vacuum Einsteins equations and the consistency of these two Einsteins equations determine the tension scalar. The universal metric, common to both strings generically does not satisfy Einsteins equation . The two metrics considered here are flat space in Minkowshi space and flat space after a special conformal transformation and the tension field behaves in such a way that strings are confined inside a light like Segment or alternatively as expanding Braneworlds where the strings are confined between two expanding bubbles separated by a very small distance at large times.

The Digital Laocoön: Replication, Narrative and Authenticity

This paper examines what qualities and affordances of a digital object allow it to emerge as a new cultural object in its own right. Due to the relationship between authenticity and replication, this is particularly important for digital objects derived from real world objects, such as digital ‘replicas’. Such objects are not an inauthentic or surrogate form of an ‘authentic’ object, but a new object with a complex relationship to the original and its own uses and affordances. The Digital Laocoön Immersive (VR exhibit), part of an AHRC funded project, was a response to the tragic fires at the Mackintosh Building of the Glasgow School of Art in 2014 and 2018. In this project a digital replica of a plaster cast of Laocoön, with a long history of use within the school, was chosen as the centre piece for the proposed immersive. As a consequence of both the immersive’s design methodology and the lessons learnt in its production, the Laocoön proved to be an ideal subject through which to critically assess the question of the status of the replica. This paper will explore not only how the material infrastructure, form and content of digital representations have an impact on its broader set relationships, but how the concept of an extended object, its production processes, and the way that these are explicitly acknowledged (or not), operate on its relationship to the original.

Tracking of Multiple Maneuvering Random Hypersurface Extended Objects Using High Resolution Sensors

With the increased resolution capability of modern sensors, an object should be considered as extended if the target extent is larger than the sensor resolution. Multiple maneuvering extended object tracking (MMEOT) uses not only measurements of the target centroid but also high-resolution sensor measurements which may resolve individual features or measurement sources. MMEOT aims to jointly estimate object number, centroid states, and extension states. However, unknown and time-varying maneuvers of multiple objects produce difficulties in terms of accurate estimation. For multiple maneuvering star-convex extended objects using random hypersurface models (RHMs) in particular, their complex maneuvering behaviors are difficult to be described accurately and handled effectively. To deal with these problems, this paper proposes an interacting multiple model Gaussian mixture probability hypothesis density (IMM-GMPHD) filter for multiple maneuvering extended object tracking. In this filter, linear maneuver models derived from RHMs are utilized to describe different turn maneuvers of star-convex extended objects accurately. Based on these, an IMM-GMPHD filtering recursive form is given by deriving new update and merging formulas of model probabilities for extended objects. Gaussian mixture components of different posterior intensities are also pruned and merged accurately. More importantly, the geometrical significance of object extension states is fully considered and exploited in this filter. This contributes to the accurate estimation of object extensions. Simulation results demonstrate the effectiveness of the proposed tracking approach—it can obtain the joint estimation of object number, kinematic states, and object extensions in complex maneuvering scenarios.

Modified Extended Object Tracker for Lidar Data Using Random Matrix Model

Random Matrix (RM) model is an effective method for modeling extended objects, and has been widely used in extended object tracking. However, the existing RM based tracking methods usually assume that the measurement models obey Gaussian distribution, which will lead to the decrease of accuracy when applied to Lidar system. This paper proposed a new observation model and used it to modified the RM smoother by considering the characteristics of Lidar data. Simulation results show that the proposed approach achieved better performance compared with the original RM tracker in Lidar system.

Communication-free autonomous cooperative circumnavigation of unpredictable dynamic objects

Each of several speed-limited planar robots is driven by the acceleration, limited in magnitude. There is an unpredictable dynamic complex object, for example, a group of moving targets or an extended moving and deforming body. The robots should reach and then repeatedly trace a certain object-dependent moving and deforming curve that encircles the object and also achieve an effective self-deployment over it. This may be, for example, the locus of points at a desired mean distance or distance from a group of targets or a single extended object, respectively. Every robot has access to the nearest point of the curve and its own velocity and “sees” the objects within a finite sensing range. The robots have no communication facilities, cannot differentiate the peers, and are to be driven by a common law. Necessary conditions for the solvability of the mission are established. Under their slight and partly unavoidable enhancement, a new decentralized control strategy is proposed and shown to solve the mission, while excluding inter-robot collisions, and for the case of a steady curve, to evenly distribute the robots over the curve and to ensure a prespecified speed of their motion over it. These are justified via rigorous global convergence results and confirmed via computer simulations.