cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Discrete Time Crystals with Absolute Stability
Creators: name: Giergiel, Krzysztof
name: Wang, Jia
name: Dalton, Bryan J.
name: Hannaford, Peter
name: Sacha, Krzysztof
Publisher: name: arXiv
Year: 2023
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We show that interacting bosons on a ring which are driven periodically by a rotating potential can support discrete time crystals whose absolute stability can be proven. The absolute stability is demonstrated by an exact mapping of discrete time crystal states to low-lying eigenstates of a time-independent model that reveals spontaneous breaking of space translation symmetry. The mapping ensures that there are no residual time-dependent terms that could lead to heating of the system and destruction of discrete time crystals. We also analyze periodically kicked bosons where the mapping is approximate only and cannot guarantee the absolute stability of discrete time crystals. Besides illustrating potential sources of instability, the kicked bosons model demonstrates a rich field for investigating the interplay between different time and space symmetry breaking, as well as the stability of time crystal behavior in contact with a thermal reservoir.
description: Version accepted for publication in Physical Review B as a Letter
Charge radii and neutron correlations in helium halo nuclei
Creators: name: Papadimitriou, G.
name: Kruppa, A. T.
name: Michel, N.
name: Nazarewicz, W.
name: Płoszajczak, M.
name: Rotureau, J.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Nuclear Theory (nucl-th)
subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: Within the complex-energy configuration interaction framework, we study correlations of valence neutrons to explain the behavior of charge radii in the neutron halo nuclei $^{6,8}$He. We find that the experimentally observed decrease of the charge radius between $^6$He and $^8$He is caused by a subtle interplay between three effects: dineutron correlations, a spin-orbit contribution to the charge radius, and a core swelling effect. We demonstrate that two-neutron angular correlations in the $2^+_1$ resonance of $^6$He differ markedly from the ground-state correlations in $^{6,8}$He.
description: 5 pages, 5 figures
Rotating quantum droplets confined in a harmonic potential
Creators: name: Nikolaou, S.
name: Kavoulakis, G. M.
name: Ogren, M.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Atomic Physics (physics.atom-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We investigate the rotational properties of a two-component, two-dimensional self-bound quantum droplet, which is confined in a harmonic potential and compare them with the well-known problem of a single-component atomic gas with contact interactions. For a fixed value of the trap frequency, choosing some representative values of the atom number, we determine the lowest-energy state, as the angular momentum increases. For a sufficiently small number of atoms, the angular momentum is carried via center-of-mass excitation. For larger values, when the angular momentum is sufficiently small, we observe vortex excitation instead. Depending on the actual atom number, one or more vortices enter the droplet. Beyond some critical value of the angular momentum, however, the droplet does not accommodate more vortices and the additional angular momentum is carried via center-of-mass excitation in a "mixed" state. Finally, the excitation spectrum is also briefly discussed.
description: 11 pages, 7 figures, changes in v2: the title was updated, the overall readability was improved, an error in the unit of $N$ was corrected, a few references were added
Hyperbolic quasi-geodesics in CAT(0) spaces
Creators: name: Sultan, Harold Mark
Publisher: name: arXiv
Year: 2011
Subjects: subject: Geometric Topology (math.GT)
subject: Group Theory (math.GR)
subject: FOS: Mathematics
subject: 20F65, 20F67

description: We prove that in CAT(0) spaces a quasi-geodesic is Morse if and only if it is contracting. Specifically, in our main theorem we prove that for $γ$ a quasi-geodesic in a CAT(0) space X, the following four statements are equivalent: (i) $γ$ is Morse, (ii) $γ$ is (b,c)--contracting, (iii), $γ$ is strongly contracting, and (iv) in every asymptotic cone $X_ω,$ any two distinct points in the ultralimit $γ_ω$ are separated by a cutpoint. As a corollary, we provide a converse to the usual Morse stability lemma in the CAT(0) setting. In addition, as a warm up we include an alternative proof of the fact that in CAT(0) spaces Morse quasi-geodesics have at least quadratic divergence, originally proven by Behrstock-Drutu.
description: 13 pages, 5 figures
Crossover from viscous fingering to fracturing in cohesive wet granular media: a photoporomechanics study
Creators: name: Meng, Yue
name: Li, Wei
name: Juanes, Ruben
Publisher: name: arXiv
Year: 2023
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: We study fluid-induced deformation and fracture of cohesive granular media, and apply photoporomechanics to uncover the underpinning grain-scale mechanics. We fabricate photoelastic spherical particles of diameter d=2mm, and make a monolayer granular pack with tunable intergranular cohesion in a circular Hele-Shaw cell that is initially filled with viscous silicone oil. We inject water into the oil-filled photoelastic granular pack, varying the injection flow rate, defending-fluid viscosity, and intergranular cohesion. We find two different modes of fluid invasion: viscous fingering, and fracturing with leak-off of the injection fluid. We directly visualize the evolving effective stress field through the particles' photoelastic response, and discover a hoop effective stress region behind the water invasion front, where we observe tensile force chains in the circumferential direction. Outside the invasion front, we observe compressive force chains aligning in the radial direction. We conceptualize the system's behavior by means of a two-phase poroelastic continuum model. The model captures granular pack dilation and compaction with the boundary delineated by the invasion front, which explains the observed distinct alignments of the force chains. Finally, we rationalize the crossover from viscous fingering to fracturing by comparing the competing forces behind the process: viscous force from fluid injection that drives fractures, and intergranular cohesion and friction that resist fractures.
On a common misunderstanding of the Birkhoff theorem and light deflection calculation: generalized Shapiro delay and its possible laboratory test
Creators: name: Zhang, Shuang-Nan
name: Yi, Shuxu
Publisher: name: arXiv
Year: 2012
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: In Newtonian gravity (NG) it is known that the gravitational field anywhere inside a spherically symmetric distribution of mass is determined only by the enclosed mass. This is also widely believed to be true in general relativity (GR), and the Birkhoff theorem is often invoked to support this analogy between NG and GR. Here we show that such an understanding of the Birkhoff theorem is incorrect and leads to erroneous calculations of light deflection and delay time through matter. The correct metric, matching continuously to the location of an external observer, is determined both by the enclosed mass and mass distribution outside. The effect of the outside mass is to make the interior clock run slower, i.e., a slower speed of light for external observer. We also discuss the relations and differences between NG and GR, in light of the results we obtained in this Lettework. Finally we discuss the Generalized Shapiro delay, caused by the outside mass, and its possible laboratory test.
description: 12 pages, 4 figures, invited talk in the 2nd Galileo-Xu Guangqi Meeing, Italy, 2011, IJMPD in press
Helicity sensitive terahertz radiation detection by field effect transistors
Creators: name: Drexler, Christoph
name: Dyakonova, Nina
name: Olbrich, Peter
name: Karch, Johannes
name: Schafberger, Michael
name: Karpierz, Krzysztof
name: Mityagin, Yuri
name: Lifshits, Masha
name: Teppe, Frederic
name: Klimenko, Oleg
name: Meziani, Yahia
name: Knap, Wojciech
name: Ganichev, Sergey
Publisher: name: arXiv
Year: 2012
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Terahertz light helicity sensitive photoresponse in GaAs/AlGaAs high electron mobility transistors. The helicity dependent detection mechanism is interpreted as an interference of plasma oscillations in the channel of the field-effect-transistors (generalized Dyakonov-Shur model). The observed helicity dependent photoresponse is by several orders of magnitude higher than any earlier reported one. Also linear polarization sensitive photoresponse was registered by the same transistors. The results provide the basis for a new sensitive, all-electric, room-temperature and fast (better than 1 ns) characterisation of all polarization parameters (Stokes parameters) of terahertz radiation. It paves the way towards terahertz ellipsometry and polarization sensitive imaging based on plasma effects in field-effect-transistors.
description: 7 pages, 4 figures
One-loop corrections, uncertainties and approximations in neutralino annihilations: Examples
Creators: name: Boudjema, Fawzi
name: La Rochelle, Guillaume Drieu
name: Kulkarni, Suchita
Publisher: name: arXiv
Year: 2011
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The extracted value of the relic density has reached the few per-cent level precision. One can therefore no longer content oneself with calculations of this observable where the annihilation processes are computed at tree-level, especially in supersymmetry where radiative corrections are usually large. Implementing full one-loop corrections to all annihilation processes that would be needed in a scan over parameters is a daunting task. On the other hand one may ask whether the bulk of the corrections are taken into account through effective couplings of the neutralino that improve the tree-level calculation and would be easy to implement. We address this issue by concentrating in this first study on the neutralino coupling to i) fermions and sfermions and ii) Z. After constructing the effective couplings we compare their efficiency compared to the full one-loop calculation and comment on the failures and success of the approach. As a bonus we point out that large non decoupling effects of heavy sfermions could in principle be measured in the annihilation process, a point of interest in view of the latest limit on the squark masses from the LHC. We also comment on the scheme dependencies of the one-loop corrected results.
Terror Management and Abortion
Creators: name: Courtney, Emily P.
name: Lee, Kirsten
Publisher: name: Open Science Framework
Year: 2023
Subjects: subject: Experimental Analysis of Behavior
subject: Social and Behavioral Sciences
subject: Social Psychology
subject: Other Psychology
subject: Psychology
subject: FOS: Psychology
subject: TERROR MANAGEMENT THEORY
subject: CAPITAL PUNISHMENT
subject: ABORTION
subject: TMT

description: Existing research within the Terror Management Theory (Greenberg et al., 1986) literature provides support for the idea that both sides of an issue (e.g., abortion regulation/accessibility) may be threatening or affirming to the ideologies of different people, which may have inherent existential implications. Specifically, abortion regulation may make existential concerns more salient for women, people with liberal political beliefs, and those who are not religious; however, and conversely, those who are men, who have more conservative political beliefs, and who are religious may instead be existentially threatened by abortion accessibility. Specific Aim: This study examines whether abortion attitudes and their relationship to ideological variables are associated with death-thought accessibility and existential concerns compared to a different but similar political issue (capital punishment). Specifically, we aim to explore the impact of ideological variables on abortion attitudes (compared to capital punishment attitudes), and whether a combination of factors will increase death thought accessibility (DTA) and existential concerns among those who are women and may be more liberal and less religious, while those who are not women, less liberal, and more religious to feel less existentially threatened. A variety of moderators will be explored.
Multivalley spin relaxation in $n$-type bulk GaAs in the presence of high electric fields
Creators: name: Tong, H.
name: Wu, M. W.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Multivalley spin relaxation in $n$-type bulk GaAs in the presence of high electric field is investigated from the microscopic kinetic spin Bloch equation approach with the $Γ$ and $L$ valleys included. We show that the spin relaxation time decreases monotonically with the electric field, which differs from the two-dimensional case and is recognized due to to the cubic form of the Dresselhauss spin-orbit coupling of the $Γ$ valley in bulk. In addition to the direct modulation of the spin relaxation time, the electric field also strongly influences the density and temperature dependences of the spin relaxation. In contrast to the monotonic decrease with increasing lattice temperature in the field-free condition, the spin relaxation time is shown to decrease more slowly under the influence of the electric field and even to increase monotonically in the case with small electron density and high electric field. We even predict a peak in weakly doped samples under moderate electric field due to the anomalous lattice-temperature dependence of the hot-electron temperature. As for the $L$ valleys, we show that instead of playing the role of a "drain" of the total spin polarization as in quantum well systems, in bulk they serve as a "momentum damping area", which prevents electrons from drifting to higher momentum states. This tends to suppress the inhomogeneous broadening and hence leads to an increase of the spin relaxation time.
description: 12 pages, 7 figures
Realizing 'quality' in Indigenous early childhood development
Creators: name: Mashon, Danielle Nichole
Publisher: name: University of British Columbia
Year: 2010

description: This study used the BC Aboriginal Child Care Society’s (BCACCS) Draft Quality Statement on Aboriginal Child Care (quality statement) as a starting point to identify Indigenous values for early childhood programming and describe how Aboriginal early childhood practitioners implement these values in Indigenous early childhood practice. Building on the view that in early childhood education, we must move ‘beyond quality to meaning-making,’ (Dahlberg, Moss & Pence, 1999), this study explored a working definition of ‘Indigenous quality care,’ comprised of five values reflected in the quality statement and supported by Indigenous early childhood education literature: Indigenous knowledge, self-determination, a holistic view of child development, family and community involvement, and Indigenous language. Using an Indigenous research methodology, I conducted audio-recorded telephone interviews with ten Aboriginal early childhood practitioners in British Columbia to identify how they operationalize the five values in practice. Findings from this study describe the successes and challenges Aboriginal early childhood practitioners face implementing programs that reflect Indigenous values for early childhood development. This study contributes to the ‘reconceptualist movement for quality care’ (Pence & Pacini-Ketchabaw, 2008) by further identifying how Indigenous notions of ‘quality’ differ from their mainstream counterparts, and sharing how mainstream notions of quality care continue to pervade the field and create challenges for Indigenous early childhood practice. Findings from this study also contribute to Indigenous early childhood education literature by sharing concrete strategies the Aboriginal early childhood practitioners in this study used to implement Indigenous values for early childhood education and care.
Reddening and metallicity maps of the Milky Way Bulge from VVV and 2MASS. I.The method and minor axis maps
Creators: name: Gonzalez, O. A.
name: Rejkuba, M.
name: Zoccali, M.
name: Valenti, E.
name: Minniti, D.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present a method to obtain reddening maps and to trace structure and metallicity gradients of the bulge using data from the recently started ESO public survey Vista Variables in the Via Lactea (VVV). We derive the mean J-Ks color of the red clump (RC) giants in 1835 subfields in the Bulge region with -8
description: Accepted for publication in A&A
Sim-Suction: Learning a Suction Grasp Policy for Cluttered Environments Using a Synthetic Benchmark
Creators: name: Li, Juncheng
name: Cappelleri, David J.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Robotics (cs.RO)
subject: Artificial Intelligence (cs.AI)
subject: FOS: Computer and information sciences

description: This paper presents Sim-Suction, a robust object-aware suction grasp policy for mobile manipulation platforms with dynamic camera viewpoints, designed to pick up unknown objects from cluttered environments. Suction grasp policies typically employ data-driven approaches, necessitating large-scale, accurately-annotated suction grasp datasets. However, the generation of suction grasp datasets in cluttered environments remains underexplored, leaving uncertainties about the relationship between the object of interest and its surroundings. To address this, we propose a benchmark synthetic dataset, Sim-Suction-Dataset, comprising 500 cluttered environments with 3.2 million annotated suction grasp poses. The efficient Sim-Suction-Dataset generation process provides novel insights by combining analytical models with dynamic physical simulations to create fast and accurate suction grasp pose annotations. We introduce Sim-Suction-Pointnet to generate robust 6D suction grasp poses by learning point-wise affordances from the Sim-Suction-Dataset, leveraging the synergy of zero-shot text-to-segmentation. Real-world experiments for picking up all objects demonstrate that Sim-Suction-Pointnet achieves success rates of 96.76%, 94.23%, and 92.39% on cluttered level 1 objects (prismatic shape), cluttered level 2 objects (more complex geometry), and cluttered mixed objects, respectively. The Sim-Suction policies outperform state-of-the-art benchmarks tested by approximately 21% in cluttered mixed scenes.
description: IEEE Transactions on Robotics
Ultrafast Control of Crystal Structure in a Topological Charge-Density-Wave Material
Creators: name: Suzuki, Takeshi
name: Kubota, Yuya
name: Mitsuishi, Natsuki
name: Akatsuka, Shunsuke
name: Koga, Jumpei
name: Sakano, Masato
name: Masubuchi, Satoru
name: Tanaka, Yoshikazu
name: Togashi, Tadashi
name: Ohsumi, Hiroyuki
name: Tamasaku, Kenji
name: Yabashi, Makina
name: Takahashi, Hidefumi
name: Ishiwata, Shintaro
name: Machida, Tomoki
name: Matsuda, Iwao
name: Ishizaka, Kyoko
name: Okazaki, Kozo
Publisher: name: arXiv
Year: 2023
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Optical control of crystal structures is a promising route to change physical properties including topological nature of a targeting material. Time-resolved X-ray diffraction measurements using the X-ray free-electron laser are performed to study the ultrafast lattice dynamics of VTe$_2$, which shows a unique charge-density-wave (CDW) ordering coupled to the topological surface states as a first-order phase transition. A significant oscillation of the CDW amplitude mode is observed at a superlattice reflection as well as Bragg reflections. The frequency of the oscillation is independent of the fluence of the pumping laser, which is prominent to the CDW ordering of the first-order phase transition. Furthermore, the timescale of the photoinduced 1$T^{\prime\prime}$ to 1$T$ phase transition is independent of the period of the CDW amplitude mode.
Drivers of social influence in the Twitter migration to Mastodon
Creators: name: La Cava, Lucio
name: Aiello, Luca Maria
name: Tagarelli, Andrea
Publisher: name: arXiv
Year: 2023
Subjects: subject: Computers and Society (cs.CY)
subject: Physics and Society (physics.soc-ph)
subject: FOS: Computer and information sciences
subject: FOS: Physical sciences

description: The migration of Twitter users to Mastodon following Elon Musk's acquisition presents a unique opportunity to study collective behavior and gain insights into the drivers of coordinated behavior in online media. We analyzed the social network and the public conversations of about 75,000 migrated users and observed that the temporal trace of their migrations is compatible with a phenomenon of social influence, as described by a compartmental epidemic model of information diffusion. Drawing from prior research on behavioral change, we delved into the factors that account for variations across different Twitter communities in the effectiveness of the spreading of the influence to migrate. Communities in which the influence process unfolded more rapidly exhibit lower density of social connections, higher levels of signaled commitment to migrating, and more emphasis on shared identity and exchange of factual knowledge in the community discussion. These factors account collectively for 57% of the variance in the observed data. Our results highlight the joint importance of network structure, commitment, and psycho-linguistic aspects of social interactions in describing grassroots collective action, and contribute to deepen our understanding of the mechanisms driving processes of behavior change of online groups.
description: Please refer to the accepted version of this paper on Scientific Reports. DOI: 10.1038/s41598-023-48200-7
Stokes IQUV Magnetic Doppler Imaging of Ap stars I. ESPaDOnS and NARVAL Observations
Creators: name: Silvester, J.
name: Wade, G. A.
name: Kochukhov, O.
name: Bagnulo, S.
name: Folsom, C. P.
name: Hanes, D.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: In this paper we describe and evaluate new spectral line polarisation observations obtained with the goal of mapping the surfaces of magnetic Ap stars in great detail. One hundred complete or partial Stokes IQUV sequences, corresponding to 297 individual polarised spectra, have been obtained for 7 bright Ap stars using the ESPaDOnS and NARVAL spectropolarimeters. The targets span a range of mass from approximately 1.8 to 3.4 solar mass, a range of rotation period from 2.56 to 6.80 days, and a range of maximum longitudinal magnetic field strength from 0.3 to over 4 kG. For 3 of the 7 stars, we have obtained dense phase coverage sampling the entire rotational cycle. These datasets are suitable for immediate magnetic and chemical abundance surface mapping using Magnetic Doppler Imaging (MDI). For the 4 remaining stars, partial phase coverage has been obtained, and additional observations will be required in order to map the surfaces of these stars. The median signal-to-noise ratio of the reduced observations is over 700 per 1.8 km\s pixel. Spectra of all stars show Stokes V Zeeman signatures in essentially all individual lines, and most stars show clear Stokes QU signatures in many individual spectral lines. The observations provide a vastly improved data set compared to previous generations of observations in terms of signal-to-noise ratio, resolving power and measurement uncertainties. Measurement of the longitudinal magnetic field demonstrates that the data are internally consistent within computed uncertainties typically at the 50 to 100 sigma level. Data are also shown to be in excellent agreement with published observations and in qualitative agreement with the predictions of published surface structure models. This study establishes the performance and stability of the ESPaDOnS and NARVAL high-resolution spectropolarimeters during the period 2006-2010.
description: 31 pages, 35 figures, 4 tables Accepted in MNRAS
Sensing and control scheme for the inteferometer configuration with an L-shaped resonator
Creators: name: Guo, Xinyao
name: Zhang, Teng
name: Martynov, Denis
name: Miao, Haixing
Publisher: name: arXiv
Year: 2023
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: The detection of high-frequency gravitational waves around kHz is critical to understanding the physics of binary neutron star mergers. A new interferometer design has been proposed in [Phys. Rev. X {\bf 13}, 021019 (2023)], featuring an L-shaped optical resonator as the arm cavity, which resonantly enhances kHz gravitational-wave signals. This new configuration has the potential to achieve better high-frequency sensitivity than the dual-recycled Fabry-Perot Michelson. In this article, we propose a sensing and control scheme for this configuration. Despite having the same number of length degrees of freedom as the dual-recycled Fabry-Perot Michelson, the new configuration requires one less degree of freedom to be controlled due to the degeneracy of two length degrees of freedom at low frequencies. We has also shown that introducing the Schnupp asymmetry is ineffective for controlling the signal-recycling cavity length. Therefore, we propose adding control fields from the dark port to control this auxiliary degree of freedom.
description: 24 pages,9 figures
Spectral classification of Pleiades brown dwarf candidates
Creators: name: Seeliger, M.
name: Neuhäuser, R.
name: Eisenbeiss, T.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We report on the results of the spectroscopy of 10 objects previously classified as brown dwarf candidates via RIJHK colors by Eisenbeiss et al. (2009), who performed deep imaging observations on a 0.4 sq.deg. field at the edge of the Pleiades. We describe and judge on classification techniques in the region of M-type stars. To classify and characterise the objects, visual and near infrared spectra have been obtained with VLT FORS and ISAAC. The spectral classification was performed using the shape of the spectra as well as spectral indices that are sensitive to the spectral type and luminosity class of Mtype stars and late M-type brown dwarfs. Furthermore a spectrophotometric distance was calculated and compared the distance of the Pleiades to investigate the membership probability. As a second argument we analyzed the proper motion. The brown dwarf candidates were found not to be brown dwarfs, but late-K to mid-M-type dwarf stars. Based on the obtained distance and tabulated proper motions we conclude that all objects are background dwarf stars.
description: 10 pages, 5 figures
Impact of Auger processes on carrier dynamics in graphene
Creators: name: Winzer, Torben
name: Malic, Ermin
Publisher: name: arXiv
Year: 2012
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: The linear, gapless bandstructure of graphene provides ideal conditions for Auger processes. They are of great importance for fundamental research and technological applications, since they qualitatively change the carrier dynamics. Time-, momentum-, and angle-resolved microscopic calculations reveal an efficient impact excitation giving rise to a significant multiplication of optically excited carriers and a remarkable Coulomb- induced carrier cooling effect. We present an analytic expression for the carrier multiplication predicting ideal conditions for its still missing experimental observation.
Kalman-filter control schemes for fringe tracking. Development and application to VLTI/GRAVITY
Creators: name: Menu, J.
name: Perrin, G.
name: Choquet, E.
name: Lacour, S.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: The implementation of fringe tracking for optical interferometers is inevitable when optimal exploitation of the instrumental capacities is desired. Fringe tracking allows continuous fringe observation, considerably increasing the sensitivity of the interferometric system. In addition to the correction of atmospheric path-length differences, a decent control algorithm should correct for disturbances introduced by instrumental vibrations, and deal with other errors propagating in the optical trains. We attempt to construct control schemes based on Kalman filters. Kalman filtering is an optimal data processing algorithm for tracking and correcting a system on which observations are performed. As a direct application, control schemes are designed for GRAVITY, a future four-telescope near-infrared beam combiner for the Very Large Telescope Interferometer (VLTI). We base our study on recent work in adaptive-optics control. The technique is to describe perturbations of fringe phases in terms of an a priori model. The model allows us to optimize the tracking of fringes, in that it is adapted to the prevailing perturbations. Since the model is of a parametric nature, a parameter identification needs to be included. Different possibilities exist to generalize to the four-telescope fringe tracking that is useful for GRAVITY. On the basis of a two-telescope Kalman-filtering control algorithm, a set of two properly working control algorithms for four-telescope fringe tracking is constructed. The control schemes are designed to take into account flux problems and low-signal baselines. First simulations of the fringe-tracking process indicate that the defined schemes meet the requirements for GRAVITY and allow us to distinguish in performance. In a future paper, we will compare the performances of classical fringe tracking to our Kalman-filter control.
description: 17 pages, 8 figures, accepted for publication in A&A
Prebiosignature Molecules Can Be Detected in Temperate Exoplanet Atmospheres with JWST
Creators: name: Claringbold, Alastair
name: Rimmer, Paul
name: Rugheimer, Sarah
name: Shorttle, Oliver
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: The search for biosignatures on exoplanets connects the fields of biology and biochemistry to astronomical observation, with the hope that we might detect evidence of active biological processes on worlds outside the solar system. Here we focus on a complementary aspect of exoplanet characterisation connecting astronomy to prebiotic chemistry: the search for molecules associated with the origin of life, prebiosignatures. Prebiosignature surveys in planetary atmospheres offer the potential to both constrain the ubiquity of life in the galaxy and provide important tests of current prebiotic syntheses outside of the laboratory setting. Here, we quantify the minimum abundance of identified prebiosignature molecules that would be required for detection by transmission spectroscopy using JWST. We consider prebiosignatures on five classes of terrestrial planet: an ocean planet, a volcanic planet, a post-impact planet, a super-Earth, and an early Earth analogue. Using a novel modelling and detection test pipeline, with simulated JWST noise, we find the detection thresholds of hydrogen cyanide (HCN), hydrogen sulfide (H2S), cyanoacetylene (HC3N), ammonia (NH3), methane (CH4), acetylene (C2H2), sulfur dioxide (SO2), nitric oxide (NO), formaldehyde (CH2O), and carbon monoxide (CO) in a variety of low mean molecular weight (<5) atmospheres. We test the dependence of these detection thresholds on M dwarf target star and the number of observed transits, finding that a modest number of transits (1-10) are required to detect prebiosignatures in numerous candidate planets, including TRAPPIST-1e with a high mean molecular weight atmosphere. We find that the NIRSpec G395M/H instrument is best suited for detecting most prebiosignatures.
description: 28 pages, 12 figures, accepted for publication in AJ
Peripheral cueing and alertness modulation over spatial interference: Shared and specific attentional mechanisms triggered by gaze and arrows
Creators: name: Marotta, Andrea
name: Ponce, Renato
name: Lupiáñez, Juan
name: Román-Caballero, Rafael
Publisher: name: Open Science Framework
Year: 2023
Subjects: subject: Cognitive Psychology
subject: Social and Behavioral Sciences
subject: Psychology
subject: FOS: Psychology
subject: social attention
subject: Gaze and Arrows
subject: Spatial Stroop

description: Following our preregistered design and hypotheses, we found interesting results in the third experiment. Thus, we have decided to conduct a fourth experiment following the same design, with the addition of two rectangular placeholders, one on each side of the fixation point during the whole task.
Detecting Adiabatic Contraction in Rotation Curves
Creators: name: Puglielli, David
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We examine the structure of adiabatically contracted Einasto profiles, using the prescriptions of Blumenthal et al. (1986) and Gnedin et al. (2004), and its impact on rotation curves. Adiabatically contracted halos display a central power index of ~0.7+/-0.1 for nearly all values of the Einasto shape parameter, alpha, and are well fit inside ~>1 kpc by double power laws. However, attempts to fit exponential disc and uncontracted halos to adiabatically contracted rotation curves yield disc masses and central power indices that are too large. We also determine whether or not the rotation curve of NGC 6503 displays evidence of adiabatic contraction using previously published bar formation constraints, and find that NGC 6503 most likely has a minimally contracted halo. However, this conclusion depends on the correct choice of circular velocity curve.
description: 37 pages, 16 figures. Accepted for publication in ApJ
Dipole-Dipole coupled double Rydberg molecules
Creators: name: Kiffner, Martin
name: Park, Hyunwook
name: Li, Wenhui
name: Gallagher, Tom F.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Atomic Physics (physics.atom-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We show that the dipole-dipole interaction between two Rydberg atoms can give rise to long range molecules. The binding potential arises from two states that converge to different separated atom asymptotes. These states interact weakly at large distances, but start to repel each other strongly as the van der Waals interaction turns into a resonant dipole-dipole interaction with decreasing separation between the atoms. This mechanism leads to the formation of an attractive well for one of the potentials. If the two separated atom asymptotes come from the small Stark splitting of an atomic Rydberg level, which lifts the Zeeman degeneracy, the depth of the well and the location of its minimum are controlled by the external electric field. We discuss two different geometries that result in a localized and a donut shaped potential, respectively.
description: 4 figures
Phonon lineshapes in the vortex state of the phonon-mediated superconductor YNi$_2$B$_2$C
Creators: name: Weber, F.
name: Pintschovius, L.
name: Hradil, K.
name: Petitgrand, D.
Publisher: name: arXiv
Year: 2012
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: We present an inelastic neutron scattering study of phonon lineshapes in the vortex state of the type-II superconductor YNi$_2$B$_2$C. In a previous study [Phys. Rev. Lett. \textbf{101}, 237002 (2008)] it was shown that certain phonons exhibit a clear signature of the superconducting gap $2Δ$ on entering the superconducting state. Our interest was to find out whether or not the lineshape of such phonons reflects the inhomogeneous nature of the vortex state induced by a magnetic field smaller than the upper critical field $B_{c2}$ .We found that this is indeed the case because the observed phonon lineshapes can be well described by a model considering the phonon as a local probe of the spatial variation of the superconducting gap. We found that even at $B=3\,\rm{T}$, where the inter-vortex distance is less than $300\,$Å, the phonon lineshape still shows evidence for a variation of the gap.
Electronic structure, dimer physics, orbital-selective behavior, and magnetic tendencies in the bilayer nickelate superconductor La$_3$Ni$_2$O$_7$ under pressure
Creators: name: Zhang, Yang
name: Lin, Ling-Fang
name: Moreo, Adriana
name: Dagotto, Elbio
Publisher: name: arXiv
Year: 2023
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: Motivated by the recently reported high-temperature superconductivity in the bilayer La$_3$Ni$_2$O$_7$ (LNO) under pressure, here we comprehensively study this system using {\it ab initio} techniques. The Ni $3d$ orbitals have a large bandwidth at ambient pressure, increasing by $\sim 22\%$ at 29.5 Gpa. Without electronic interactions, the Ni $d_{3z^2-r^2}$ orbitals form a bonding-antibonding molecular orbital state via the O $p_z$ inducing a ``dimer'' lattice in the LNO bilayers. The Fermi surface consists of two-electron sheets with mixed $e_g$ orbitals and a hole pocket defined by the $d_{3z^2-r^2}$ orbital, suggesting a Ni two-orbital minimum model. Different from the infinite-layer nickelate, we obtained a large {\it interorbital} hopping between $d_{3z^2-r^2}$ and $d_{x^2-y^2}$ states in LNO, caused by the ligand ``bridge'' of in-plane O $p_x$ or $p_y$ orbitals connecting those two orbitals, inducing $d-p$ $σ$-bonding characteristics. The competition between the intraorbital and interorbital hoppings leads to an interesting dominant spin stripe ($π$, 0) order because of bond ferromagnetic tendencies via the recently discussed ``half-empty'' mechanism.
description: 6 pages, 4 figures
Shared Stewardship of Research Data
Creators: name: Humphrey, Chuck
Publisher: name: Portage
Year: 2016

description: Data and its computation have become daily news topics. The Globe and Mail February 3 article on Canada’s inadequate big data computing capacity, and a recent announcement by the International Committee of Medical Journal Editors (ICMJE) proposing that all authors share the de-identified individual-patient data underlying the results in their articles, are only 2 of many examples. The editors of the New England Journal of Medicine responded to ICMJE with an editorial on "research parasites," stating that the culture of data sharing is far from being universally embraced. Underlying this news is the importance of research data management and the importance of Research Libraries in implementing Research Data Management strategies. Chuck will speak about developments in research data management services and infrastructure across Canada and about the support Portage will provide Canadian higher education institutions. He will discuss collaborative initiatives between the library community and other research stakeholders, including the January 27th announced memorandum of agreement with Compute Canada and emerging data policies from funding agencies. Time will be included for a good discussion. Portage aims to coordinate and expand existing library-based expertise, services and infrastructure so that Canadian researchers will have access to the support they need for research data management (RDM). Portage will have two major components: a network of expertise to provide access in both English and French to a comprehensive set of resources, tools and experts; and a preservation and discovery system to connect the various infrastructure and service components needed for national preservation and discovery of data. Chuck Humphrey has supported data services at the University of Alberta since 1992, and has worked on numerous regional, national and international initiatives to increase access to data for teaching and research purposes. He was involved in OECD Global Science Forums on Data and Research Infrastructure for the Social Sciences in 2010-2011 and on Ethics and Big Data in 2014-2015. Chuck was the lead investigator on a University of Alberta Libraries’ successful application for a data centre in the Canadian International Polar Year (IPY) Data Assembly Centres Network, which has now become the Canadian Polar Data Network. He currently serves on the Steering Committee of Research Data Canada; is a Board member of the Consortia Advancing Standards in Research Administrative Information; and has been a key participant in CARL’s Project ARC working group, which developed the vision and framework for Portage.
Gamma-Flash Generation in Multi-Petawatt Laser-Matter Interactions
Creators: name: Hadjisolomou, P.
name: Jeong, T. M.
name: Kolenaty, D.
name: Macleod, A. J.
name: Olšovcová, V.
name: Versaci, R.
name: Ridgers, C. P.
name: Bulanov, S. V.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Plasma Physics (physics.plasm-ph)
subject: FOS: Physical sciences

description: The progressive development of high power lasers over the last several decades, enables the study of $γ$-photon generation when an intense laser beam interacts with matter, mainly via inverse Compton scattering at the high intensity limit. $γ$-ray flashes are a phenomenon of broad interest, drawing attention of researchers working in topics ranging from cosmological scales to elementary particle scales. Over the last few years, a plethora of studies predict extremely high laser energy to $γ$-photon energy conversion using various target and/or laser field configurations. The aim of the present manuscript is to discuss several recently proposed $γ$-ray flash generation schemes, as a guide for upcoming $γ$-photon related experiments and for further evolution of the presently available theoretical schemes.
description: 12 pages, 8 figures
Functional characterization of H2-M3-restricted CD8⁺ T cells in innate and adaptive immunity
Creators: name: Chow, Michael T.
Publisher: name: University of British Columbia
Year: 2010

description: The outcome of many host immune responses to perturbations caused by pathogenic infections is dependent on the coordinated actions between innate and adaptive immune cells. Despite the seemingly clear distinction immune cells belongs either to the innate or adaptive immune system, CD8⁺ T cells that exhibit properties attributed to both compartments of the immune system exist. Specifically, a subset of MHC class Ib molecules, H2-M3, preferentially binds to and presents formylated-peptides to CD8⁺ T cells resulting in their rapid expansion, quick production of cytokines, and provision of cytolytic protection against bacterial infections. The work in this thesis is focused on the discovery and characterization of the immunoregulatory potential of H2-M3-restricted T cells. Specifically, the activation of H2-M3-restricted T cells provided early signals for the efficient priming of antigen-specific CD4⁺ T cell responses following immunization, which translated to augmented CD4⁺ T cell numbers during the acute, effector, and memory phase following bacterial infection. Augmented CD4⁺ T cell responses generated with additional signals derived from activated H2-M3-restricted T cells also significantly increased primary antigen-specific responses by conventional MHC class Ia-restricted CD8⁺ T cells. Importantly, a second MHC class Ib molecule, Qa-1, whose human equivalent is HLA-E, was also identified to augment CD4⁺ T cell responses, in vivo. The ability for H2-M3-restricted T cells to provide help to the helper CD4⁺ T cells, leading to an increase in total numbers, was not the result of an increase in cellular division events, but rather due to an increase in CD4⁺ T cell survival. Using in vitro co-culture assays, it was determined that H2-M3-restricted T cells perform these functions by inducing the maturation of dendritic cells. Interestingly, H2-M3-restricted T cells were found to be more efficient at performing this function, relative to activated natural killer cells. Therefore, the adjuvant-like properties of innate-like H2-M3-restricted T cells, and possibly other MHC class Ib-restricted T cells, are targets with unique attributes that can be harnessed for future vaccine design strategies to potently focus immune responses against microbial infections.
Photon radiation by relatively slowly rotating fermions in magnetic field
Creators: name: Buzzegoli, Matteo
name: Kroth, Jonathan D.
name: Tuchin, Kirill
name: Vijayakumar, Nandagopal
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: We study the electromagnetic radiation by a fermion carrying an electric charge $q$ embedded in a medium rotating with constant angular velocity $\bfΩ$ parallel or anti-parallel to an external constant magnetic field $\bf B$. We assume that the rotation is "relatively slow"; namely, that the angular velocity $Ω$ is much smaller than the inverse magnetic length $\sqrt{qB}$. In practice, such angular velocity can be extremely high. The fermion motion is a superposition of two circular motions: one due to its rigid rotation caused by forces exerted by the medium, another due to the external magnetic field. We derive an exact analytical expression for the spectral rate and the total intensity of this type of synchrotron radiation. Our numerical calculations indicate very high sensitivity of the radiation to the angular velocity of rotation. We show that the radiation intensity is strongly enhanced if $q\bf B$ and $\bf Ω$ point in the opposite directions and is suppressed otherwise.
description: 35 pages, 10 Figures; v2: minor errors fixed; v3: published version
Bilayer graphene as an helical quantum Hall ferromagnet
Creators: name: Cote, R.
name: Fouquet, J. P.
name: Luo, Wenchen
Publisher: name: arXiv
Year: 2011
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: The two-dimensional electron gas in a bilayer graphene in the Bernal stacking supports a variety of uniform broken-symmetry ground states in Landau level N=0 at integer filling factors $ν\in [-3,4].$ When an electric potential difference (or bias) is applied between the layers at filling factors $ν=-1,3$, the ground state evolves from an interlayer coherent state at small bias to a state with orbital coherence at higher bias where \textit{electric} dipoles associated with the orbital pseudospins order spontaneously in the plane of the layers. In this paper, we show that by further increasing the bias at these two filling factors, the two-dimensional electron gas goes first through a Skyrmion crystal state and then into an helical state where the pseudospins rotate in space. The pseudospin textures in both the Skyrmion and helical states are due to the presence of a Dzyaloshinskii-Moriya interaction in the effective pseudospin Hamiltonian when orbital coherence is present in the ground state. We study in detail the electronic structure of the helical and Skyrmion crystal states as well as their collective excitations and then compute their electromagnetic absorption.
description: 17 pages, 17 postscript figures