Black Hole Entropy from a Highly Excited Elementary String

Suggested correspondence between a black hole and a highly excited elementary string is explored. Black hole entropy is calculated by computing the density of states for an open excited string. We identify the square root of oscillator number of the excited string with Rindler energy of black hole to obtain an entropy formula which, not only agrees at the leading order with the Bekenstein-Hawking entropy, but also reproduces the logarithmic correction obtained for black hole entropy in the quantum geometry framework. This provides an additional supporting evidence for correspondence between black holes and strings.Comment: revtex, 4 page

Crack Growth from Naturally Occurring Material Discontinuities in Operational Aircraft

AbstractThis paper focuses on problems associated with aircraft sustainment related issues and illustrates how cracks that grow from small naturally occurring material discontinuities in operational aircraft behave. The example discussed in this paper, which is associated with crack growth under a representative maritime aircraft load spectrum, when taken in conjunction with previous studies into cracks growing under combat aircraft load spectra illustrates how for cracks that grow from naturally occurring material discontinuities under such operational load spectra there is generally little crack closure so that the crack growth history from its initial equivalent pre-crack size (EPS) through to final failure can be easily and accurately computed

Communication and optimal hierarchical networks

We study a general and simple model for communication processes. In the model, agents in a network (in particular, an organization) interchange information packets following simple rules that take into account the limited capability of the agents to deal with packets and the cost associated to the existence of open communication channels. Due to the limitation in the capability, the network collapses under certain conditions. We focus on when the collapse occurs for hierarchical networks and also on the influence of the flatness or steepness of the structure. We find that the need for hierarchy is related to the existence of costly connections.Comment: 7 pages, 2 figures. NATO ARW on Econophysic

Using social robots for language learning: are we there yet?

Along with the development of speech and language technologies and growing market interest, social robots have attracted more academic and commercial attention in recent decades. Their multimodal embodiment offers a broad range of possibilities, which have gained importance in the education sector. It has also led to a new technology-based field of language education: robot-assisted language learning (RALL). RALL has developed rapidly in second language learning, especially driven by the need to compensate for the shortage of first-language tutors. There are many implementation cases and studies of social robots, from early government-led attempts in Japan and South Korea to increasing research interests in Europe and worldwide. Compared with RALL used for English as a foreign language (EFL), however, there are fewer studies on applying RALL for teaching Chinese as a foreign language (CFL). One potential reason is that RALL is not well-known in the CFL field. This scope review paper attempts to fill this gap by addressing the balance between classroom implementation and research frontiers of social robots. The review first introduces the technical tool used in RALL, namely the social robot, at a high level. It then presents a historical overview of the real-life implementation of social robots in language classrooms in East Asia and Europe. It then provides a summary of the evaluation of RALL from the perspectives of L2 learners, teachers and technology developers. The overall goal of this paper is to gain insights into RALL’s potential and challenges and identify a rich set of open research questions for applying RALL to CFL. It is hoped that the review may inform interdisciplinary analysis and practice for scientific research and front-line teaching in future

Freedom comes at a cost?: An exploratory study on affordances’ impact on users’ perception of a social robot

Along with the development of speech and language technologies, the market for speech-enabled human-robot interactions (HRI) has grown in recent years. However, it is found that people feel their conversational interactions with such robots are far from satisfactory. One of the reasons is the habitability gap, where the usability of a speech-enabled agent drops when its flexibility increases. For social robots, such flexibility is reflected in the diverse choice of robots’ appearances, sounds and behaviours, which shape a robot’s ‘affordance’. Whilst designers or users have enjoyed the freedom of constructing a social robot by integrating off-the-shelf technologies, such freedom comes at a potential cost: the users’ perceptions and satisfaction. Designing appropriate affordances is essential for the quality of HRI. It is hypothesised that a social robot with aligned affordances could create an appropriate perception of the robot and increase users’ satisfaction when speaking with it. Given that previous studies of affordance alignment mainly focus on one interface’s characteristics and face-voice match, we aim to deepen our understanding of affordance alignment with a robot’s behaviours and use cases. In particular, we investigate how a robot’s affordances affect users’ perceptions in different types of use cases. For this purpose, we conducted an exploratory experiment that included three different affordance settings (adult-like, child-like, and robot-like) and three use cases (informative, emotional, and hybrid). Participants were invited to talk to social robots in person. A mixed-methods approach was employed for quantitative and qualitative analysis of 156 interaction samples. The results show that static affordance (face and voice) has a statistically significant effect on the perceived warmth of the first impression; use cases affect people’s perceptions more on perceived competence and warmth before and after interactions. In addition, it shows the importance of aligning static affordance with behavioural affordance. General design principles of behavioural affordances are proposed. We anticipate that our empirical evidence will provide a clearer guideline for speech-enabled social robots’ affordance design. It will be a starting point for more sophisticated design guidelines. For example, personalised affordance design for individual or group users in different contexts

Is honesty the best policy for mismatched partners? Aligning multi-modal affordances of a social robot: an opinion paper

Spoken interactions between a human user and an artificial device (such as a social robot) have attracted much attention in recent decades (Lison and Meena, 2014; Oracle, 2020). Shifting from automation robots in the industrial domain, social robots are expected to be used in social domains, such as the service industry, education, healthcare, and entertainment (Bartneck et al., 2020, p.163). According to Darling (2016)’s definition, a social robot is “a physically embodied, autonomous agent that communicates and interacts with humans on an emotional level”. Many features play important roles in interactions with a social robot, such as people’s experience with technology products, expectations of social robots, interactional environments and other features such as a social robot’s appearance, voice and behaviours. In this last regard, affordance design affects how people perceive a social robot and how such perception affects their behaviours and experiences. The term “affordance” was invented by ecological psychologist Gibson (1977), who proposed that our perception of what it is possible to do with objects is shaped by their form. Affordance indicates what users see and can do with an object in a given situation; it is about perceptual action possibilities in an environment (Matei, 2020). A strong tendency in social robot affordance design is to make human-robot interaction (HRI) resemble human-human interaction (HHI). It is hoped in many studies that robots designed with anthropomorphic appearances and human-like cognitive behaviours can enable humans to interact with them in similar ways as they would interact with other humans, even to develop social bonds (Leite et al., 2013; Kahn et al., 2015; Koyama et al., 2017; Ligthart et al., 2018). However, there are concerns about this approach. In fact, speech-based artificial agents’ conversational interaction with human users is far from natural, and the language used tends to be formulaic (Moore et al., 2016). One of the reasons behind this is a significant change in the applications of spoken human-agent interaction (HAI) along the evolution of spoken language technology applications (Moore, 2017a). Compared with “command and control systems” of the 1970s and contemporary smartphone-based “personal assistants”, social robots are expected to be used in more dynamic and open environments. This implies that users’ expectations, demands and ways to interact with spoken agents differ depending on the use case. What has succeeded before in real-time spoken HAI (e.g., voice command for specific uses) may not work well for social robots in some contacts. Additionally, a social robot’s human-like affordances could be seen as “dishonest” because such signals hide the fact that a social robot has limited interactive capabilities and is a “mismatched” conversational partner (Moore, 2015; 2017b). What’s more, the approach to constructing a robot by integrating off-the-shelf human-like technologies lacks an appreciation of the function and behaviour of speech in a broader theoretical framework (Moore, 2015). This paper takes a step back to consider what human users look for when speaking to a social robot. It starts by looking at the nature and the process of spoken interactions. It then discusses why honesty is the best policy for a social robot in HRI. Furthermore, the arguments presented here support the hypothesis that aligning a social robot’s external affordances coherently with internal capabilities can shape its usability and improve human users’ experience in HRI

Signature of short distance physics on inflation power spectrum and CMB anisotropy

The inflaton field responsible for inflation may not be a canonical fundamental scalar. It is possible that the inflaton is a composite of fermions or it may have a decay width. In these cases the standard procedure for calculating the power spectrum is not applicable and a new formalism needs to be developed to determine the effect of short range interactions of the inflaton on the power spectrum and the CMB anisotropy. We develop a general formalism for computing the power spectrum of curvature perturbations for such non-canonical cases by using the flat space K\"all\'en-Lehmann spectral function in curved quasi-de Sitter space assuming implicitly that the Bunch-Davis boundary conditions enforces the inflaton mode functions to be plane wave in the short wavelength limit and a complete set of mode functions exists in quasi-de Sitter space. It is observed that the inflaton with a decay width suppresses the power at large scale while a composite inflaton's power spectrum oscillates at large scales. These observations may be vindicated in the WMAP data and confirmed by future observations with PLANCK.Comment: 17 pages, 4 figures, Extended journal version, Accepted for publication in JCA

Rapidity distribution as a probe for elliptical flow at intermediate energies

Interplay between the spectator and participant matter in heavy-ion collisions is investigated within isospin dependent quantum molecular dynamics (IQMD) model in term of rapidity distribution of light charged particles. The effect of different types and size rapidity distributions is studied in elliptical flow. The elliptical flow patterns show important role of the nearby spectator matter on the participant zone. This role is further explained on the basis of passing time of the spectator and expansion time of the participant zone. The transition from the in-plane to out-of-plane is observed only when the mid-rapidity region is included in the rapidity bin, otherwise no transition occurs. The transition energy is found to be highly sensitive towards the size of the rapidity bin, while weakly on the type of the rapidity distribution. The theoretical results are also compared with the experimental findings and are found in good agreement.Comment: 8 figure

Dynamical approach to spectator fragmentation in Au+Au reactions at 35 MeV/A

The characteristics of fragment emission in peripheral $^{197}$Au+$^{197}$Au collisions 35 MeV/A are studied using the two clusterization approaches within framework of \emph{quantum molecular dynamics} model. Our model calculations using \emph{minimum spanning tree} (MST) algorithm and advanced clusterization method namely \emph{simulated annealing clusterization algorithm} (SACA) showed that fragment structure can be realized at an earlier time when spectators contribute significantly toward the fragment production even at such a low incident energy. Comparison of model predictions with experimental data reveals that SACA method can nicely reproduce the fragment charge yields and mean charge of the heaviest fragment. This reflects suitability of SACA method over conventional clusterization techniques to investigate spectator matter fragmentation in low energy domain.Comment: 6 pages, 5 figures, accepte

Quantum Kinetic Theory III: Simulation of the Quantum Boltzmann Master Equation

We present results of simulations of a em quantum Boltzmann master equation (QBME) describing the kinetics of a dilute Bose gas confined in a trapping potential in the regime of Bose condensation. The QBME is the simplest version of a quantum kinetic master equations derived in previous work. We consider two cases of trapping potentials: a 3D square well potential with periodic boundary conditions, and an isotropic harmonic oscillator. We discuss the stationary solutions and relaxation to equilibrium. In particular, we calculate particle distribution functions, fluctuations in the occupation numbers, the time between collisions, and the mean occupation numbers of the one-particle states in the regime of onset of Bose condensation.Comment: 12 pages, 15 figure