Towards binocular active vision in a robot head system

This paper presents the first results of an investigation and pilot study into an active, binocular vision system that combines binocular vergence, object recognition and attention control in a unified framework. The prototype developed is capable of identifying, targeting, verging on and recognizing objects in a highly-cluttered scene without the need for calibration or other knowledge of the camera geometry. This is achieved by implementing all image analysis in a symbolic space without creating explicit pixel-space maps. The system structure is based on the ‘searchlight metaphor’ of biological systems. We present results of a first pilot investigation that yield a maximum vergence error of 6.4 pixels, while seven of nine known objects were recognized in a high-cluttered environment. Finally a “stepping stone” visual search strategy was demonstrated, taking a total of 40 saccades to find two known objects in the workspace, neither of which appeared simultaneously within the Field of View resulting from any individual saccade

Preprint arXiv: 2106.05030 Submitted on 9 Jun 2021

Non-Hermitian Hamiltonians, which effectively describe dissipative systems, and analogue gravity models, which simulate properties of gravitational objects, comprise seemingly different areas of current research. Here, we investigate the interplay between the two by relating parity-time-symmetric dissipative Weyl-type Hamiltonians to analogue Schwarzschild black holes emitting Hawking radiation. We show that the exceptional points of these Hamiltonians form tilted cones mimicking the behavior of the light cone of a radially infalling observer approaching a black hole horizon. We further investigate the presence of tunneling processes, reminiscent of those happening in black holes, in a concrete example model. We interpret the non-trivial result as the purely thermal contribution to analogue Hawking radiation in a Schwarzschild black hole. Assuming that our particular Hamiltonian models a photonic crystal of experimental relevance, we argue that the loss from the latter in the form of thermal radiation can be interpreted as the blackbody contribution to analogue black hole radiation when measuring at the exceptional cone. As such, these systems are promising candidates for black hole analogue models

PT symmetry-protected exceptional cones and analogue Hawking radiation

We show that the exceptional surfaces of linear three-dimensional non-Hermitian parity-time-symmetric two-band models attain the form of topologically stable tilted exceptional cones. By relating the exceptional cones to energy cones of two-dimensional Hermitian parity-time-symmetric two-band models, we find a connection between the exceptional cone and the light cone of an observer in the vicinity of a Schwarzschild black hole. When the cone overtilts, light-like particle-antiparticle pairs are created resembling Hawking radiation. We also investigate dissipative features of the non-Hermitian Hamiltonian related to the latter and comment on potential realizations in laboratory setups

Data Driven Flavour Model

A bottom-up approach has been adopted to identify a flavour model that agrees with present experimental measurements. The charged fermion mass hierarchies suggest that only the top Yukawa term should be present at the renormalisable level. Similarly, describing the lightness of the active neutrinos through the type-I Seesaw mechanism, right-handed neutrino mass terms should also be present at the renormalisable level. The flavour symmetry of the Lagrangian including the fermionic kinetic terms and only the top Yukawa is then a combination of $U(2)$ and $U(3)$ factors. Once considering the Majorana neutrino terms, the associated symmetry is $O(3)$. Lighter charged fermion and active neutrino masses and quark and lepton mixings arise considering specific spurion fields {\it \`a la} Minimal Flavour Violation. The associated phenomenology is investigated and the model turns out to have almost the same flavour protection as the Minimal Flavour Violation in both quark and lepton sectors. Promoting the spurions to dynamical fields, the associated scalar potential is also studied and a minimum is identified such that fermion masses and mixings are correctly reproduced. Very precise predictions for the Majorana phases follow from the minimisation of the scalar potential and thus the neutrinoless-double-beta decay may represent a smoking gun for the model.Comment: 39 pages, 6 figures. Accepted for publication in EPJ

Antimicrobial removal on piglets promotes health and higher bacterial diversity in the nasal microbiota

The view on antimicrobials has dramatically changed due to the increased knowledge on the importance of microbiota composition in different body parts. Antimicrobials can no longer be considered only beneficial, but also potentially deleterious for favourable bacterial populations. Still, the use of metaphylactic antimicrobial treatment at early stages of life is a practice in use in porcine production. Many reports have shown that antibiotics can critically affect the gut microbiota, however the effect of perinatal antimicrobial treatment on the nasal microbiota has not been explored yet. To gain insights on the potential changes in nasal microbial composition due to antimicrobial treatments, piglets from two different farms were sampled at weaning. The nasal microbiota was analysed when antimicrobial treatment was used early in life, and later, when no antimicrobial treatment was used during the lactation period. Removal of perinatal antimicrobials resulted in an increased bacterial diversity in nasal microbiota at weaning. Concurrently, elimination of antimicrobials produced an increase in the relative abundance of Prevotella and Lactobacillus, and a decrease in Moraxella and Bergeyella. These changes in microbiota composition were accompanied by an improvement of the piglets' health and a higher productivity in the nursery phase

The Deficit of Distant Galaxy Clusters in the RIXOS X-ray Survey

Clusters of galaxies are the largest gravitationally bound systems and therefore provide an important way of studying the formation and evolution of the large scale structure of the Universe. Cluster evolution can be inferred from observations of the X-ray emission of the gas in distant clusters, but interpreting these data is not straightforward. In a simplified view, clusters grow from perturbations in the matter distribution: their intracluster gas is compressed and shock-heated by the gravitational collapse$^{1}$. The resulting X-ray emission is determined by the hydrostatic equilibrium of the gas in the changing gravitational potential. However, if processes such as radiative cooling or pre-collapse heating of the gas are important, then the X-ray evolution will be strongly influenced by the thermal history of the gas. Here we present the first results from a faint flux-limited sample of X-ray selected clusters compiled as part of the ROSAT International X-ray and Optical Survey (RIXOS). Very few distant clusters have been identified. Most importantly, their redshift distribution appears to be inconsistent with simple models based on the evolution of the gravitational potential. Our results suggest that radiative cooling or non-gravitational heating of the intracluster gas must play an important role in the evolution of clusters.Comment: uuencoded compressed postscript. The preprint is also available at http://www.ast.cam.ac.uk/preprint/PrePrint.htm