High-Energy theory for close Randall Sundrum branes

We obtain an effective theory for the radion dynamics of the two-brane Randall Sundrum model, correct to all orders in brane velocity in the limit of close separation, which is of interest for studying brane collisions and early Universe cosmology. Obtained via a recursive solution of the Bulk equation of motions, the resulting theory represents a simple extension of the corresponding low-energy effective theory to the high energy regime. The four-dimensional low-energy theory is indeed not valid when corrections at second order in velocity are considered. This extension has the remarkable property of including only second derivatives and powers of first order derivatives. This important feature makes the theory particularly easy to solve. We then extend the theory by introducing a potential and detuning the branes.Comment: Version published in the Physical Review

DECENTRALIZED MULTIAGENT METAREASONING APPLICATIONS IN TASK ALLOCATION AND PATH FINDING

Decentralized task allocation and path finding are two problems for multiagent systems where no single fixed algorithm provides the best solution in all environments. Past research has considered metareasoning approaches to these problems that take in map, multiagent system, or communication information. None of these papers address the application of metareasoning about individual agent state features which could decrease communication and increase performance for decentralized systems. This thesis presents the application of a meta-level policy that is conducted offline using supervised learning through extreme gradient boosting. The multiagent system used here operates under full communication, and the system uses an independent multiagent metareasoning structure. This thesis describes research that developed and evaluated metareasoning approaches for the multiagent task allocation problem and the multiagent path finding problem. For task allocation, the metareasoning policy determines when to run a task allocation algorithm. For multiagent path finding, the metareasoning policy determines which algorithm an agent should use. The results of this comparative research suggest that this metareasoning approach can reduce communication and computational overhead without sacrificing performance

High-energy effective theory for matter on close Randall Sundrum branes

Extending the analysis of hep-th/0504128, we obtain a formal expression for the coupling between brane matter and the radion in a Randall-Sundrum braneworld. This effective theory is correct to all orders in derivatives of the radion in the limit of small brane separation, and, in particular, contains no higher than second derivatives. In the case of cosmological symmetry the theory can be obtained in closed form and reproduces the five-dimensional behaviour. Perturbations in the tensor and scalar sectors are then studied. When the branes are moving, the effective Newtonian constant on the brane is shown to depend both on the distance between the branes and on their velocity. In the small distance limit, we compute the exact dependence between the four-dimensional and the five-dimensional Newtonian constants.Comment: Updated version as published in PR

Characterization of stellar companion from high-contrast long-slit spectroscopy data: The EXtraction Of SPEctrum of COmpanion (EXOSPECO) algorithm

High-contrast long-slit spectrographs can be used to characterize exoplanets. High-contrast long-slit spectroscopic data are however corrupted by stellar leakages which largely dominate other signals and make the process of extracting the companion spectrum very challenging. This paper presents a complete method to calibrate the spectrograph and extract the signal of interest. The proposed method is based on a flexible direct model of the high-contrast long-slit spectroscopic data. This model explicitly accounts for the instrumental response and for the contributions of both the star and the companion. The contributions of these two components and the calibration parameters are jointly estimated by solving a regularized inverse problem. This problem having no closed-form solution, we propose an alternating minimization strategy to effectively find the solution. We have tested our method on empirical long-slit spectroscopic data and by injecting synthetic companion signals in these data. The proposed initialization and the alternating strategy effectively avoid the self-subtraction bias, even for companions observed very close to the coronagraphic mask. Careful modeling and calibration of the angular and spectral dispersion laws of the instrument clearly reduce the contamination by the stellar leakages. In practice, the outputs of the method are mostly driven by a single hyper-parameter which tunes the level of regularization of the companion SED.Comment: Paper under review by Astronomy & Astrophysic

Using Unmanned Aerial Vehicle (UAV) Imagery to Characterise Pursuit-Diving Seabird Association With Tidal Stream Hydrodynamic Habitat Features

Acknowledgments We gratefully acknowledge the support of colleagues at Marine Scotland Science, the crew and scientists of the MRV Scotia 2018 cruise (particularly Chief Scientist Adrian Tait) and ERI interns: Gael Gelis and Martin Forestier. We gratefully acknowledge the constructive comments from reviewers. Finally, we also want to thank Ella Benninghaus for providing the auk illustrations used within the paper. Funding This work was funded by the Bryden Centre project, supported by the European Union’s INTERREG VA Programme, and managed by the Special EU Programmes Body (SEUPB). The views and opinions expressed in this paper do not necessarily reflect those of the European Commission or the Special EU Programmes Body (SEUPB). Aspects of this research were also funded by a Royal Society Research Grant [RSG\R1\180430], the NERC VertIBase project [NE/N01765X/1], the UK Department for Business, Energy, and Industrial Strategy’s offshore energy Strategic Environmental Assessment programme and EPSRC Supergen ORE Hub [EP/S000747/1].Peer reviewedPublisher PD

Faster Secret Keys for (T)FHE

GLWE secret keys come with some associated public information, like their size or the distribution probability of their coefficients. Those information have an impact on the FHE algorithms, their computational cost, their noise growth, and the overall security level. In this paper, we identify two limitations with (T)FHE: there is no fine-grained control over the size of a GLWE secret key, and there is a minimal noise variance which leads to an unnecessary increment of the level of security with large GLWE secret keys. We introduce two (non exclusive) new types of secret keys for GLWE-based cryptosystems, that are designed to overcome the aforementioned limitations. We explain why these are as secure as the traditional ones, and detail all the improvements that they brought to the FHE algorithms. We provide many comparisons with state-of-the-art TFHE techniques, and benchmarks showing computational speed-ups between $1.3$ and $2.4$ while keeping the same level of security and failure probability. Furthermore, the size of the public material (i.e., key switching and bootstrapping keys) is also reduced by factors from $1.5$ and $2.7$

Lattice-based (Partially) Blind Signature without Restart

We present in this paper a blind signature and its partially blind variant based on lattices assumptions. Blind signature is a cornerstone in privacy-oriented cryptography and we propose the first lattice based scheme without restart. Compare to related work, the key idea of our construction is to provide a trapdoor to the signer in order to let him perform some gaussian pre-sampling during the signature generation process, preventing this way to restart from scratch the whole protocol. We prove the security of our scheme under the ring k-SIS assumption, in the random oracle model. We also explain security issues in the other existing lattice-based blind signature schemes. Finally, we propose a partially blind variant of our scheme, which is done with no supplementary cost, as the number of elements generated and exchanged during the signing protocol is exactly the same

Global population and conservation status of the Great Black-backed Gull Larus marinus

The Great Black-backed Gull Larus marinus is a generalist species that inhabits temperate and arctic coasts of the north Atlantic Ocean. In recent years, there has been growing concern about population declines at local and regional scales; however, there has been no attempt to robustly assess Great Black-backed Gull population trends across its global range. We obtained the most recent population counts across the species’ range and analysed population trends at a global, continental, and national scale over the most recent three-generation period (1985–2021) following IUCN Red List criteria. We found that, globally, the species has declined by 43%–48% over this period (1.2–1.3% per annum, respectively), from an estimated 291,000 breeding pairs to 152,000–165,000 breeding pairs under two different scenarios. North American populations declined more steeply than European ones (68% and 28%, respectively). We recommend that Great Black-backed Gull should be uplisted from ‘Least Concern’ to ‘Vulnerable’ on the IUCN Red List of Threatened Species under criterion A2 (an estimated reduction in population size >30% over three generations). Larus gulls; gull populations; population assessment; population ecology; bird conservationpublishedVersio

Reduced breeding success in great black-backed gulls (Larus marinus) due to harness-mounted GPS device

Animal-borne bio-logging devices are routinely fitted to seabirds to learn about their behaviour and physiology, as well as their interactions with the marine environment. The assessment and reporting of deleterious impacts from such devices on the individuals carrying them is critical to inform future work and improve data quality and animal welfare. We assessed the impacts of thoracic-harness attachments on the breeding performance and inter-annual return rates of Great Black-backed Gulls. We found that tagged individuals hatched fewer eggs per nest (0.67) than two different control groups (handled but not tagged – 2.0, and not handled – 1.9) and had lower hatching success rates per nest (27% compared with 81% and 82% in control groups). Inter-annual return rates were similar between tagged and control groups, but the harness attachment potentially caused the death of an individual 5 days after deployment. Overall, the harness attachment was a lead driver of nest failure. We urge extreme caution for those wanting to use harness-mounted devices on Great Black-backed Gulls