cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Mapping out SU(5) GUTs with non-Abelian discrete flavor symmetries
Creators: name: Plentinger, Florian
name: Seidl, Gerhart
Publisher: name: arXiv
Year: 2008
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We construct a class of supersymmetric SU(5) GUT models that produce nearly tribimaximal lepton mixing, the observed quark mixing matrix, and the quark and lepton masses, from discrete non-Abelian flavor symmetries. The SU(5) GUTs are formulated on two five-dimensional throats in the flat limit and the neutrino masses become small due to the type-I seesaw mechanism. The discrete non-Abelian flavor symmetries are given by semi-direct products of cyclic groups that are broken at the infrared branes at the tip of the throats. As a result, we obtain SU(5) GUTs that provide a combined description of non-Abelian flavor symmetries and quark-lepton complementarity.
description: 5 pages, 3 figures, RevTeX. References and comments added. Final version to appear in Phys. Rev. D
The effect of droplet coalescence on drag in turbulent channel flows
Creators: name: Cannon, Ianto
name: Izbassarov, Daulet
name: Tammisola, Outi
name: Brandt, Luca
name: Rosti, Marco E.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences
subject: 76T10

description: We study the effect of droplet coalescence on turbulent wall-bounded flows, by means of direct numerical simulations. In particular, the volume-of-fluid and front-tracking methods are used to simulate turbulent channel flows containing coalescing and non-coalescing droplets, respectively. We find that coalescing droplets have a negligible effect on the drag, whereas the non-coalescing ones steadily increase drag as the volume fraction of the dispersed phase increases: indeed, at 10\% volume fraction, the non-coalescing droplets show a 30\% increase in drag, whereas the coalescing droplets show less than 4\% increase. We explain this by looking at the wall-normal location of droplets in the channel and show that non-coalescing droplets enter the viscous sublayer, generating an interfacial shear stress which reduces the budget for viscous stress in the channel. On the other hand, coalescing droplets migrate towards the bulk of the channel forming large aggregates, which hardly affect the viscous shear stress while damping the Reynolds shear stress. We prove this by relating the mean viscous shear stress integrated in the wall-normal direction to the centreline velocity.
description: 11 pages, 7 figures
DDOTI Observations of Gravitational-Wave Sources Discovered in O3
Creators: name: Becerra, R. L.
name: Dichiara, S.
name: Watson, A. M.
name: Troja, E.
name: Butler, N. R.
name: Pereyra, M.
name: Méndez, E. Moreno
name: De Colle, F.
name: Lee, W. H.
name: Kutyrev, A. S.
name: López, K. O. C.
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We present optical follow-up observations with the DDOTI telescope of gravitational-wave events detected during the Advanced LIGO and Advanced Virgo O3 observing run. DDOTI is capable of responding to an alert in a few minutes, has an instantaneous field of about 69 deg$^{2}$, and obtains $10σ$ upper limits of $w_{\rm lim}=18.5$ to 20.5 AB mag in 1000~s of exposure, depending on the conditions. We observed 54\% (26 out of 48) of the unretracted gravitational-wave alerts and did not find any electromagnetic counterparts. We compare our upper limits to various possible counterparts: the kilonova AT~2017gfo, models of radioactive- and magnetar-powered kilonovae, short gamma-ray burst afterglows, and AGN flares. Although the large positional uncertainties of GW sources do not allow us to place strong constraints during O3, DDOTI observations of well-localized GW events in O4 and beyond could meaningfully constrain models of compact binary mergers. We show that DDOTI is able to detect kilonovae similar to AT~2017gfo up to about 200~Mpc and magnetar-powered kilonovae up to 1~Gpc. We calculate that nearby ($\lesssim$200 Mpc) afterglows have a high chance ($\approx$70\%) to be detected by rapid ($\lesssim$3 hours) DDOTI observations if observed on-axis, whereas off-axis afterglows are unlikely to be seen. Finally, we suggest that long-term monitoring of massive BBH events with DDOTI could confirm or rule out late AGN flares associated with these events.
description: 26 pages, 5 figures. Accepted for publication in MNRAS
Ρομαντικός Μιλιταρισμός: Από τις Απαρχές ως τον Σημερινό Κόσμο
Creators: name: Τατίδου, Σοφία Παύλου
Publisher: name: Aristotle University of Thessaloniki
Year: 2017
Subjects: Ρομαντισμός
Μιλιταρισμός
Ρομαντικός Μιλιταρισμός
Romanticism
Militarism
Romantic Militarism

description: Σκοπός τούτης της εργασίας είναι η μελέτη του ρομαντικού μιλιταρισμού ως προς τη φύση και την εξέλιξή του. Το φαινόμενο έχει ως αφετηρία του τις αρχές του 19ου αιώνα, που βρισκόταν στην επαναστατική του φάση, ακολουθεί η κλιμάκωσή του με την αποικιακή εξάπλωση που ακολούθησε το 1873, ενώ το αποκορύφωμα, αλλά και παράλληλα το τέλος του, απαντά στον Α’ Παγκόσμιο Πόλεμο. Ψήγματά του, ωστόσο, εντοπίζονται και στον σύγχρονο κόσμο και πιο συγκεκριμένα στα διάφορα κινήματα ένοπλης διαμαρτυρίας που εκδηλώνονται ανά την υφήλιο. Φυσικά, το πέρασμά του από τις διάφορες ιστορικές φάσεις δε θα μπορούσε να αφήσει τον χαρακτήρα του αναλλοίωτο. Έτσι, ο πρώτος λογοτεχνικός ενθουσιασμός γύρω από τον πόλεμο, έδωσε τη θέση του στην πολεμική συμμετοχή για τα πολιτικά δικαιώματα μέσα από το νομιμοποιητικό ιδεολόγημα του «πολιτισμού», για να βρει ξανά ζωή, μετααποικιακά πλέον, στον ένοπλο αγώνα. Όλα τα παραπάνω είναι τα κομμάτια που συνθέτουν την ιστορία του φαινομένου και παράλληλα θα αποτελέσουν τον κορμό τούτης της έρευνας, που θα στηριχθεί κυρίως στην ξένη βιβλιογραφία, ενώ πολύτιμη γνώση θα προσφέρει και το ανάλογο οπτικοακουστικό υλικό
description: The aim of this study is to analyse the nature and evolution of “romantic militarism”. The origins of the phenomenon hail back to the 19th century. It first appeared in its revolutionary phase. Later it intensified during the colonial expansion that followed in 1873, and finally reached its peak and conclusion in the aftermath of World War I. Traces of this phenomenon, however, can also be found in the modern world, and more specifically in the various armed protest movements that occur worldwide. Naturally, the character of “romantic nationalism” could not remain unaltered through its various historical phases. Thus, the first enthusiasm about war, as it appeared in literature, gave way to militant involvement in civil rights through the legitimizing ideology of “culture”, and reappeared in armed struggles in the postcolonial period. All these are parts that make up the history of the phenomenon and will also comprise the basis for this kind of research, which relies mainly on international bibliography, while valuable knowledge can also be obtained from relevant audiovisual material
The Compact Discontinuous Galerkin (CDG) Method for Elliptic Problems
Creators: name: Peraire, Jaume
name: Persson, Per-Olof
Publisher: name: arXiv
Year: 2007
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics
subject: 65M60, 65M12, 65M15

description: We present a compact discontinuous Galerkin (CDG) method for an elliptic model problem. The problem is first cast as a system of first order equations by introducing the gradient of the primal unknown, or flux, as an additional variable. A standard discontinuous Galerkin (DG) method is then applied to the resulting system of equations. The numerical interelement fluxes are such that the equations for the additional variable can be eliminated at the element level, thus resulting in a global system that involves only the original unknown variable. The proposed method is closely related to the local discontinuous Galerkin (LDG) method [B. Cockburn and C.-W. Shu, SIAM J. Numer. Anal., 35 (1998), pp. 2440-2463], but, unlike the LDG method, the sparsity pattern of the CDG method involves only nearest neighbors. Also, unlike the LDG method, the CDG method works without stabilization for an arbitrary orientation of the element interfaces. The computation of the numerical interface fluxes for the CDG method is slightly more involved than for the LDG method, but this additional complication is clearly offset by increased compactness and flexibility. Compared to the BR2 [F. Bassi and S. Rebay, J. Comput. Phys., 131 (1997), pp. 267-279] and IP [J. Douglas, Jr., and T. Dupont, in Computing Methods in Applied Sciences (Second Internat. Sympos., Versailles, 1975), Lecture Notes in Phys. 58, Springer, Berlin, 1976, pp. 207-216] methods, which are known to be compact, the present method produces fewer nonzero elements in the matrix and is computationally more efficient.
description: 25 pages, 2 figures, 7 tables
Μοντελοποίηση και Προσομοίωση Συστήματος Jungle Computing
Creators: name: Τσίτσια, Ευαγγελία Βασιλείου
Publisher: name: Aristotle University of Thessaloniki
Year: 2017
Subjects: Προσομοίωση-απόδοση-Ζούγκλα
Jungle computing
Cloud

description: Τα τελευταία χρόνια, η ραγδαία εξέλιξη του Internet και η ολοένα αυξανόμενη ταχύτητα των δικτύων σε συνδυασμό με την συνεχώς αυξανόμενη υπολογιστική ισχύ άλλαξαν τον τρόπο διαχείρισης και επεξεργασίας των πληροφοριών, προσφέροντας λύσεις σε προβλήματα που ήταν αδύνατο να επιλυθούν με τις παλαιότερες τεχνολογίες. Τα συστήματα υψηλών επιδόσεων και η κατανεμημένη επεξεργασία είναι πλέον ευρύτατα διαδεδομένα στην επιστημονική κοινότητα. Ανάμεσα στις πλατφόρμες που είναι διαθέσιμες στους επιστήμονες συγκαταλέγονται τα grid, cluster και τα cloud. Αυτές οι υποδομές διανύουν μια περίοδο ριζικών αλλαγών λόγω της εμφάνισης των τεχνολογιών πολλών πυρήνων που αφενός προσφέρουν βελτιωμένη ταχύτητα επεξεργασίας αλλά αφετέρου αυξάνουν την ανομοιογένεια και την πολυπλοκότητα των πλατφόρμων. Επιπρόσθετα, η ανάγκη για υπολογιστική ισχύ και υψηλή διαθεσιμότητα υλικού, η ετερογένεια του λογισμικού και ζητήματα όπως η κατανομή των δεδομένων συχνά οδηγούν στο συνδυασμό πολλαπλών cluster, grid, cloud και άλλων συστημάτων ταυτόχρονα. Με αποτέλεσμα όλα αυτά μαζί να συνιστούν μια υπολογιστική ζούγκλα (Jungle Computing). Σε αυτή την εργασία περιγράφονται οι έννοιες του κατανεμημένου συστήματος, του cloud και του jungle computing και προσδιορίζονται τα βασικά χαρακτηριστικά τους. Έπειτα, μελετάται η απόδοση ενός συστήματος jungle computing και συγκρίνεται με την απόδοση ενός απλού κατανεμημένου συστήματος. Τέλος, ερευνάται ο ρόλος του αλγορίθμου που χρησιμοποιείται για τη δρομολόγηση των εργασιών στους επεξεργαστές και της πειθαρχίας ουράς στην απόδοση του συστήματος
description: In recent years, rapid Internet development and improvements in the speed of broadband networks in conjunction with the constantly growing computing power have changed the way we manage and process information, offering solutions to problems unsolved until now. In this way high-performance and distributed computing have great impact on scientific practice. Among the most vastly available platforms to scientists are clusters, grids, and cloud systems. Such infrastructures currently are experiencing revolutionary change owing to the integration of many-core technologies that on one hand improve computational speed, but on the other they increase heterogeneity and complexity of the platforms. Further complexities arise because urgent desire for scalability and issues including data distribution, software heterogeneity, and ad hoc hardware availability commonly force scientists into simultaneous use of multiple platforms (e.g. clusters, grids, and clouds used concurrently)• a true computing jungle. This essay provides a definition for distributed systems, cloud and jungle computing and the key characteristics of them are determined. Moreover, jungle computing performance is analyzed and compared to distributed system performance
Substrate-controlled dynamics of spin qubits in low dimensional van-der-Waals materials
Creators: name: Onizhuk, Mykyta
name: Galli, Giulia
Publisher: name: arXiv
Year: 2021
Subjects: subject: Quantum Physics (quant-ph)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: We report a theoretical study of the coherence dynamics of spin qubits in two-dimensional materials (2DMs) and van-der-Waals heterostructures, as a function of the host thickness and the composition of the surrounding environment. We focus on MoS$_2$ and WS$_2$, two promising systems for quantum technology applications, and we consider the decoherence arising from the interaction of the spin qubit with nuclear spins. We show that the Hahn-echo coherence time is determined by a complex interplay between the source of decoherence in the qubit host and in the environment, which in turn determines whether the noise evolution is in a classical or quantum mechanical regime. We suggest that the composition and thickness of van-der-Waals heterostructures encapsulating a qubit host can be engineered to maximize coherence times. Finally, we discuss how quantum sensors may be able to probe the dynamics of the nuclear bath in 2DMs.
description: 6 pages, 4 figures
Accelerating Solutions of Perfect Fluid Hydrodynamics for Initial Energy Density and Life-Time Measurements in Heavy Ion Collisions
Creators: name: Csorgo, T.
name: Nagy, M. I.
name: Csanad, M.
Publisher: name: arXiv
Year: 2007
Subjects: subject: Nuclear Theory (nucl-th)
subject: Astrophysics (astro-ph)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Experiment (nucl-ex)
subject: FOS: Physical sciences

description: A new class of accelerating, exact, explicit and simple solutions of relativistic hydrodynamics is presented. Since these new solutions yield a finite rapidity distribution, they lead to an advanced estimate of the initial energy density and life-time of high energy heavy ion reactions. Accelerating solutions are also given for spherical expansions in arbitrary number of spatial dimensions.
description: 3 pages, labels in Fig.2b corrected. Based on T. Csorgo's talk at the XXXVIth Int. Symp. Multiparticle Dynamics (ISMD 2006), Paraty, RJ, Brazil. Submitted to the Brazilian Journal of Physics
No Cauchy Horizon Theorem for Nonlinear Electrodynamics Black Holes with Charged Scalar Hairs
Creators: name: An, Yu-Sen
name: Li, Li
name: Yang, Fu-Guo
Publisher: name: arXiv
Year: 2021
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We prove a no Cauchy horizon theorem for general nonlinear electrodynamics black holes with charged scalar hairs. By constructing a radially conserved charged, we show that there is no inner Cauchy horizon for both spherical and planar symmetric cases, independent of the form of scalar potential and nonlinear electrodynamics. After imposing the null energy condition, we are also able to rule out the existence of the Cauchy horizon for the hyperbolic black holes. We take the Born-Infeld black hole as a concrete example to study the interior dynamics beyond the event horizon. When the contribution from the scalar potential can be neglected, the asymptotic near-singularity takes a universal Kasner form. We also confirm that the intricate interior dynamics is closely associated with the instability of the inner Cauchy horizon triggered by scalar hairs.
description: 12 pages, 6 figures. Comments are welcomed
Dark Energy from Casimir Energy on Noncommutative Extra Dimensions
Creators: name: Fabi, S.
name: Harms, B.
name: Karatheodoris, G.
Publisher: name: arXiv
Year: 2006
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We study the possibility that dark energy is a manifestation of the Casimir energy on extra dimensions with the topology of $S^2$. We consider our universe to be $M^4 \times S^2$ and modify the geometry by introducing noncommutativity on the extra dimensions only, i.e. replacing $S^2$ with the fuzzy version $S_{F}^2$. We find the energy density as a function of the size of the representation $M+1$ of the algebra of $S_{F}^2$, and we calculate its value for the $M+1=2$ case. The value of the energy density turns out to be positive, i.e. provides dark energy, and the size of the extra dimensions agrees with the experimental limit. We also recover the correct commutative limit as the noncommutative parameter goes to zero.
description: 6 pages, RevTeX4
The effect of coal composition upon gas sorption and transmissibility of bituminous coal
Creators: name: Clarkson, Christopher Raymond
Publisher: name: University of British Columbia
Year: 2009

description: The effect of bituminous coal composition, particularly the organic fraction, upon gas sorption and transmissibility is investigated. Micropore capacities of bituminous coals, determined from low pressure carbon dioxide adsorption, show a general increase with total and structured vitrinite content. Conversely, micropore capacities generally decrease with an increase in inertinite and mineral matter content. High pressure methane monolayer capacities show a similar trend. Micropore size distributions indicate an increase in the total number of micropores and a slight decrease in mean pore diameter with vitrinite content. Mesopore volumes and surface areas, determined through nitrogen sorption, show a general decrease with vitrinite content and increase with inertinite content of bituminous coal. Vitrinite therefore contains more microporosity and less mesoporosity than inertinite. Hysteresis loops of sorption isotherms indicate that mesopores of the coals studied are slit-shaped. Permeabilities of bituminous coals obtained through the use of a permeameter capable of measuring permeabilities on a bed-by-bed scale show that brighter coal lithotypes are more permeable than dull lithotypes. The order of decreasing permeability with lithotype is: bright> banded> fibrous > banded dull> dull. The increase in permeability with increased brightness of coals is due to the presence of abundant macrofracturing (cleating) in bright coal. For one sample, permeabilties were found to increase with vitrinite content.
Energy-consistent finite difference schemes for compressible hydrodynamics and magnetohydrodynamics using nonlinear filtering
Creators: name: Iijima, Haruhisa
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computational Physics (physics.comp-ph)
subject: Numerical Analysis (math.NA)
subject: Fluid Dynamics (physics.flu-dyn)
subject: Plasma Physics (physics.plasm-ph)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: In this paper, an energy-consistent finite difference scheme for the compressible hydrodynamic and magnetohydrodynamic (MHD) equations is introduced. For the compressible magnetohydrodynamics, an energy-consistent finite difference formulation is derived using the product rule for the spatial difference. The conservation properties of the internal, kinetic, and magnetic energy equations can be satisfied in the discrete level without explicitly solving the total energy equation. The shock waves and discontinuities in the numerical solution are stabilized by nonlinear filtering schemes. An energy-consistent discretization of the filtering schemes is also derived by introducing the viscous and resistive heating rates. The resulting energy-consistent formulation can be implemented with the various kinds of central difference, nonlinear filtering, and time integration schemes. The second- and fifth-order schemes are implemented based on the proposed formulation. The conservation properties and the robustness of the present schemes are demonstrated via one- and two-dimensional numerical tests. The proposed schemes successfully handle the most stringent problems in extremely high Mach number and low beta conditions.
description: 31 pages, 11 figures, accepted for publication in Journal of Computational Physics
On the Conformal Symmetry of Exceptional Scalar Theories
Creators: name: Farnsworth, Kara
name: Hinterbichler, Kurt
name: Hulik, Ondrej
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: The DBI and special galileon theories exhibit a conformal symmetry at unphysical values of the spacetime dimension. We find the Lagrangian form of this symmetry. The special conformal transformations are non-linearly realized on the fields, even though conformal symmetry is unbroken. Commuting the conformal transformations with the extended shift symmetries, we find new symmetries, which when taken together with the conformal and shift symmetries close into a larger algebra. For DBI this larger algebra is the conformal algebra of the higher dimensional bulk in the brane embedding view of DBI. For the special galileon it is a real form of the special linear algebra. We also find the Weyl transformations corresponding to the conformal symmetries, as well as the necessary improvement terms to make the theories Weyl invariant, to second order in the coupling in the DBI case and to lowest order in the coupling in the special galileon case.
description: 23 pages
Analogue models for Schwarzschild and Reissner-Nordström spacetimes
Creators: name: de Oliveira, Christyan C.
name: Mosna, Ricardo A.
name: Pitelli, João Paulo M.
name: Richartz, Maurício
Publisher: name: arXiv
Year: 2021
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Mathematical Physics (math-ph)
subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: We present analogue models for the Schwarzschild and Reissner-Nordström (RN) spacetimes based on unidirectional hydrodynamic flows. We show that, with appropriate coordinate transformations, sound waves in a moving fluid propagate as scalar fields at the equatorial sections of Schwarzschild and RN black holes. The coordinate associated with the direction of the flow plays the role of the radial coordinate in standard Schwarzschild/RN coordinates, while the transversal spatial coordinate is related to the angular coordinate on each equatorial slice. The magnitude of the flow velocity is related to the mass and charge of the analogue black hole. Physical quantities like pressure and density remain finite at the analogue horizon, thereby resulting in sound waves that are well defined almost everywhere, except possibly at the analogue black hole singularity.
description: 8 pages, 7 figures. Matches published version
Unusual photoemission resonances of oxygen-dopant induced states in Bi$_{2}$Sr$_2$CaCu$_2$O$_{8+x}$
Creators: name: Richard, P.
name: Pan, Z. -H.
name: Neupane, M.
name: Fedorov, A. V.
name: Valla, T.
name: Johnson, P. D.
name: Gu, G. D.
name: Ku, W.
name: Wang, Z.
name: Ding, H.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: We have performed an angular-resolved photoemission study of underdoped, optimally doped and overdoped Bi$_{2}$Sr$_2$CaCu$_2$O$_{8+x}$ samples using a wide photon energy range (15 - 100 eV). We report a small and broad non-dispersive A$_{1g}$ peak in the energy distribution curves whose intensity scales with doping. We attribute it to a local impurity state similar to the one observed recently by scanning tunneling spectroscopy and identified as the oxygen dopants. Detailed analysis of the resonance profile and comparison with the single-layered Bi$_{2}$Sr$_2$CuO$_{6+x}$ suggest a mixing of this local state with Cu via the apical oxygens.
description: 4 pages, 4 figures
Relativistic outflows from a GRMHD mean-field disk dynamo
Creators: name: Vourellis, Christos
name: Fendt, Christian
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We present simulations of thin accretion disks around black holes investigating a mean-field disk dynamo in our resistive GRMHD code (Vourellis et al. 2019) that is able to produce a large scale magnetic flux. We consider a weak seed field in an initially thin disk, a background (turbulent) magnetic diffusivity and the dynamo action. A standard quenching mechanism is applied to mitigate the otherwise exponential increase of the magnetic field. Comparison simulations of an initial Fishbone-Moncrief torus suggest that reconnection may provide another quenching mechanism. The dynamo-generated magnetic flux expands from the disk interior into the disk corona, becomes advected by disk accretion, and fills the axial region of the domain. The dynamo leads to an initially rapid increase in magnetic energy and flux, while for later evolutionary stages the growth stabilizes. Accretion towards the black hole depends strongly on the magnetic field structure that develops. The radial field component supports extraction of angular momentum and thus accretion. It also sets the conditions for launching a disk wind, initially from inner disk area. When a strong field has engulfed the disk, strong winds are launched that are predominantly driven by the pressure gradient of the toroidal field. For rotating black holes we identify a Poynting flux-dominated jet, driven by the Blandford-Znajek mechanism. This axial Poynting flux is advected from the disk and therefore accumulates at the expense of the flux carried by the disk wind, that is itself regenerated by the disk dynamo.
description: 26 pages, 16 Figures, accepted for publication in ApJ
The Far Ultraviolet M-dwarf Evolution Survey. I. The Rotational Evolution of High-Energy Emissions
Creators: name: Pineda, J. Sebastian
name: Youngblood, Allison
name: France, Kevin
Publisher: name: arXiv
Year: 2021
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: M-dwarf stars are prime targets for exoplanet searches because of their close proximity and favorable properties for both planet detection and characterization. However, the potential habitability and atmospheric characterization of these exoplanetary systems depends critically on the history of high-energy stellar radiation from X-rays to NUV, which drive atmospheric mass loss and photochemistry in the planetary atmospheres. With the Far Ultraviolet M-dwarf Evolution Survey (FUMES) we have assessed the evolution of the FUV radiation, specifically 8 prominent emission lines, including Ly$α$, of M-dwarf stars with stellar rotation period and age. We demonstrate tight power-law correlations between the spectroscopic FUV features, and measure the intrinsic scatter of the quiescent FUV emissions. The luminosity evolution with rotation of these spectroscopic features is well described by a broken power-law, saturated for fast rotators, and decaying with increasing Rossby number, with a typical power-law slope of $-2$, although likely shallower for Ly$α$. Our regression fits enable FUV emission line luminosity estimates relative to bolometric from known rotation periods to within $\sim$0.3 dex, across 8 distinct UV emission lines, with possible trends in the fit parameters as a function of source layer in the stellar atmosphere. Our detailed analysis of the UV luminosity evolution with age further shows that habitable zone planets orbiting lower-mass stars experience much greater high-energy radiative exposure relative the same planets orbiting more massive hosts. Around early-to-mid M-dwarfs these exoplanets, at field ages, accumulate up to 10-20$\times$ more EUV energy relative to modern Earth. Moreover, the bulk of this UV exposure likely takes place within the first Gyr of the stellar lifetime.
description: Accepted to AAS Journals, paper 1 of series
Self-Sustaining Vortices in Protoplanetary Disks: Setting the Stage for Planetary System Formation
Creators: name: Regaly, Zsolt
name: Kadam, Kundan
name: Dullemond, Cornelis P.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: The core accretion scenario of planet formation assumes that planetesimals and planetary embryos are formed during the primordial, gaseous phases of the protoplanetary disk. However, how the dust particles overcome the traditional growth barriers is not well understood. The recently proposed viscous ring-instability may explain the concentric rings observed in protoplanetary disks by assuming that the dust grains can reduce the gas conductivity, which can weaken the magneto-rotational instability. We present an analysis of this model with the help of GPU-based numerical hydrodynamic simulations of coupled gas and dust in the thin-disk limit. During the evolution of the disk the dusty rings become Rossby unstable and break up into a cascade of small-scale vortices. The vortices form secularly stable dusty structures, which could be sites of planetesimal formation by the streaming instability as well as direct gravitational collapse. The phenomenon of self-sustaining vortices is consistent with observational constraints of exoplanets and sets a favorable environment for planetary system formation.
description: 10 pages, accepted for publication in MNRAS
OH Megamasers in HI Surveys: Forecasts and a Machine Learning Approach to Separating Disks from Mergers
Creators: name: Roberts, Hayley
name: Darling, Jeremy
name: Baker, Andrew J.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: OH megamasers (OHMs) are rare, luminous masers found in gas-rich major galaxy mergers. In untargeted neutral hydrogen ($\mathrm{HI}$) emission-line surveys, spectroscopic redshifts are necessary to differentiate the $λ_\text{rest}=18$ cm masing lines produced by OHMs from $\mathrm{HI}$ 21 cm lines. Next generation $\mathrm{HI}$ surveys will detect an unprecedented number of galaxies, most of which will not have spectroscopic redshifts. We present predictions for the numbers of OHMs that will be detected and the potential "contamination" they will impose on $\mathrm{HI}$ surveys. We examine Looking at the Distant Universe with the MeerKAT Array (LADUMA), a single-pointing deep-field survey reaching redshift $z_\mathrm{HI}=1.45$, as well as potential future surveys with the Square Kilometre Array (SKA) that would observe large portions of the sky out to redshift $z_\mathrm{HI}=1.37$. We predict that LADUMA will potentially double the number of known OHMs, creating an expected contamination of 1.0% of the survey's $\mathrm{HI}$ sample. Future SKA $\mathrm{HI}$ surveys are expected to see up to 7.2% OH contamination. To mitigate this contamination, we present methods to distinguish $\mathrm{HI}$ and OHM host populations without spectroscopic redshifts using near- to mid-IR photometry and a k-Nearest Neighbors algorithm. Using our methods, nearly 99% of OHMs out to redshift $z_\mathrm{OH} \sim 1.0$ can be correctly identified. At redshifts out to $z_\mathrm{OH}\sim2.0$, 97% of OHMs can be identified. The discovery of these high-redshift OHMs will be valuable for understanding the connection between extreme star formation and galaxy evolution.
description: 14 pages, 11 figures, accepted for publication in ApJ
Inspecting the Cepheid distance ladder: The Hubble Space Telescope distance to the SNIa host galaxy NGC 5584
Creators: name: Javanmardi, Behnam
name: Mérand, Antoine
name: Kervella, Pierre
name: Breuval, Louise
name: Gallenne, Alexandre
name: Nardetto, Nicolas
name: Gieren, Wolfgang
name: Pietrzyński, Grzegorz
name: Hocdé, Vincent
name: Borgniet, Simon
Publisher: name: arXiv
Year: 2021
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: The current tension between the direct and the early Universe measurements of the Hubble Constant, $H_0$, requires detailed scrutiny of all the data and methods used in the studies on both sides of the debate. The Cepheids in the type Ia supernova (SNIa) host galaxy NGC 5584 played a key role in the local measurement of $H_0$. The SH0ES project used the observations of this galaxy to derive a relation between Cepheids' periods and ratios of their amplitudes in different optical bands of the Hubble Space Telescope (HST), and used these relations to analyse the light curves of the Cepheids in around half of the current sample of local SNIa host galaxies. In this work, we present an independent detailed analysis of the Cepheids in NGC 5584. We employ different tools for our photometric analysis and a completely different method for our light curve analysis, and we do not find a systematic difference between our period and mean magnitude measurements compared to those reported by SH0ES. By adopting a period-luminosity relation calibrated by the Cepheids in the Milky Way, we measure a distance modulus $μ=31.810\pm0.047$ (mag) which is in agreement with $μ=31.786\pm0.046$ (mag) measured by SH0ES. In addition, the relations we find between periods and amplitude ratios of the Cepheids in NGC 5584 are significantly tighter than those of SH0ES and their potential impact on the direct $H_0$ measurement will be investigated in future studies.
description: Accepted for publication in The Astrophysical Journal on 17-Feb-2021
Comparative Analysis of Civil Protection Systems
Creators: name: Δαδούδη, Αικατερίνη Κωνσταντίνου
Publisher: name: Aristotle University of Thessaloniki
Year: 2017
Subjects: Πολιτική Προστασία
Διαχείριση Έκτακτης Ανάγκης
Καταστροφές
Civil Protection
Emergency Management
Disasters

description: Τις τελευταίες δεκαετίες συμβαίνουν ολοένα και περισσοτερα καταστροφικά φαινόμενα και καταστάσεις εκτάκτου ανάγκης με αποτέλεσμα να τονίζεται η ανάγκη ενίσχυσης της πολιτικής προστασίας. Οι περισσότερες χώρες και διεθνείς οργανισμοί έχουν προσανατολιστεί προς αυτή την κατεύθυνση δημιουργώντας μηχανισμούς πολιτικής προστασίας με στόχο την αποτελεσματική αντίδραση στην έκτακτη ανάγκη, μέσω της διεθνούς συνεργασίας. Με τη συγκριτική ανάλυση ορισμένων χωρών, καταλήγουμε ότι για την αντιμετώπιση μιας κρίσης χρειάζεται οπωσδήποτε ένα καλά οργανωμένο σύστημα πολιτικής προστασίας. Μέσω αποτελεσματικού σχεδιασμού αντιμετώπισης καταστάσεων εκτάκτου ανάγκης και διαχείρισης κρίσεων, πολλά γεγονότα μπορούν να προληφθούν ή τουλάχιστον να ελαχιστοποιηθούν οι ζημίες και οι απώλειες που προκλείνονται από αυτά. Μέσω των μειονεκτημάτων και των ελλείψεων που διαπιστώθηκαν, όλες οι χώρες μπορούν να επωφεληθούν και να βελτιώσουν τις πρακτικές και στρατηγικές τους για την αντιμετώπιση καταστροφών. Κάθε χώρα θα πρέπει να έχει την τεχνογνωσία να ενημερώσει επαρκώς τους πολιτες της και να είναι προετοιμασμένοι για τις ιδιαιτερότητες που μπορεί να αντιμετωπίσουν. Μέσω της συνεργασίας των οργανισμών εκτάκτου ανάγκης, του κράτους και των πολιτών, καθώς και της προσπάθειας για συνεχή βελτίωση, τα καταστροφικά γεγονότα μπορούν να μειωθούν στο ελάχιστο
description: As emergencies and disastrous phenomena occur increasingly during last decades, emphasize is given to the need of civil protection reinforcement. Most countries and international organizations orient to this direction by establishing civil protection mechanisms aiming to an effective emergency response, through the international cooperation. By comparative analysis of some countries, resulted in that the crucial role on dealing crisis is a well-organized civil protection system. Through effective emergency response planning and crisis management, a lot of events can be prevented or at least minimize damages and losses if happened. Through the bottlenecks and deficiencies detected, all countries can be benefitted to get better and adopt best practices and strategies to deal with disasters. Each country should have the knowledge to appropriate aware its citizens and be prepared for the peculiarities may deal with. Through cooperation of the emergency agencies, state and citizens as well as through the attempt for constant improvements, the destructive events can be eliminated to the minimum
On cylindrically bounded $H$-Hypersurfaces of $\mathbb{H}^{n}\times \mathbb{R}$
Creators: name: Bessa, G. Pacelli
name: Costa, Silvana M.
Publisher: name: arXiv
Year: 2006
Subjects: subject: Differential Geometry (math.DG)
subject: FOS: Mathematics

description: We show that $H$-hypersurfaces of $\mathbb{H}^{n}\times \mathbb{R}$ contained in a vertical cylinder and with Ricci curvature with strong quadratic decay have mean curvature $| H| > (n-1)/n$.
description: 6 pages
Finite-momentum energy dynamics in a Kitaev magnet
Creators: name: Metavitsiadis, Alexandros
name: Brenig, Wolfram
Publisher: name: arXiv
Year: 2021
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We study the energy-density dynamics at finite momentum of the two-dimensional Kitaev spin-model on the honeycomb lattice. Due to fractionalization of magnetic moments, the energy relaxation occurs through mobile Majorana matter, coupled to a static $\mathbb{Z}_2$ gauge field. At finite temperatures, the $\mathbb{Z}_2$ flux excitations act as an emergent disorder, which strongly affects the energy dynamics. We show that sufficiently far above the flux proliferation temperature, but not yet in the classical regime, gauge disorder modifies the coherent low-temperature energy-density dynamics into a form which is almost diffusive, with hydrodynamic momentum scaling of a diffusion-kernel, which however remains retarded, primarily due to the presence of two distinct relaxation channels of particle-hole and particle-particle nature. Relations to thermal conductivity are clarified. Our analysis is based on complementary calculations in the low-temperature homogeneous gauge and a mean-field treatment of thermal gauge fluctuations, valid at intermediate and high temperatures.
description: 9 pages, 8 figures. arXiv admin note: text overlap with arXiv:1909.09360
R-tree performance evaluation and optimization
Creators: name: Αθανασίου, Νικόλαος Γεωργίου
Publisher: name: Aristotle University of Thessaloniki
Year: 2017
Subjects: Χωρική ευρετηρίαση δεδομένων
R Δένδρο
Βελτιστοποίηση
Spatial indexing
R-tree
Optimization

description: Η χωρική ευρετηρίαση δεδομένων είναι από τις πιο σημαντικές τεχνικές που χρησιμοποιούνται σε μία χωρική βάση δεδομένων, κάνοντας εφικτή την λειτουργία τους σε μεγάλα σύνολα δεδομένων. Χωρίς αυτή, κάθε χωρικό ερώτημα θα κατέληγε σε σειριακή αναζήτηση. Στην εποχή των “big data” είναι εξαιρετικής σημασίας η ικανότητα ενός συστήματος να επεκτείνεται σε όλο και μεγαλύτερα datasets κάτι που είναι ιδιαίτερα δύσκολο στην περίπτωση που τα δεδομένα περιέχουν γεωμετρική πληροφορία. Οι χωρικές δομές ευρετηρίασης επιτυγχάνουν αυτό το στόχο επιβάλλοντας μια οργανωτική δομή επί των δεδομένων. Στην παρούσα διπλωματική εργασία μελετούμε και βελτιστοποιούμε μια από τις πιο σημαντικές δομές χωρικής ευρετηρίασης, το R-δένδρο
description: Spatial indexing is one of the key techniques in spatial databases, making operations on large datasets possible. Without indexing, any spatial query would fall-back to a brute force search of every record. In the big data era, it is of outmost importance a system’s ability to scale to ever increasing datasets, a task particularly difficult for data that contain geometric information and the respective operations that we request on it; spatial indexes achieve this by imposing an organization structure to our data. The present thesis elaborates and optimizes one of the most important such structures, the R-tree
Μαγνητική υπερθερμία νανοσωματιδίων: Μελέτη ομοιωμάτων ιστών και ex vivo
Creators: name: Καλπαξίδου, Ζωή Παναγιώτη
Publisher: name: Aristotle University of Thessaloniki
Year: 2017
Subjects: Μαγνητική υπερθερμία
ομοιώματα ιστών
ex vivo
Magnetic hyperthermia
phantom tissues

description: Σκοπός της διπλωματικής εργασίας ήταν η μελέτη της μαγνητικής υπερθερμίας νανοσωματιδίων σε ομοιώματα ιστών και σε ιστούς ζωικής προέλευσης. Αρχικά εξετάστηκαν οι θερμικές επιδόσεις μαγνητικών νανοσωματιδίων σε υδατικά διαλύματα. Στόχος αυτών των πειραμάτων ήταν ο καθορισμός της βέλτιστης συγκέντρωσης και του βέλτιστου όγκου των σιδηρορευστών, που χρησιμοποιήθηκαν για τα επόμενα πειράματα. Στη συνέχεια, έγινε έγχυση των σιδηρορευστών αυτών σε ομοιώματα ιστών από αγαρόζη, που συντέθηκαν στο εργαστήριο, για να εφαρμοστεί μαγνητική υπερθερμία. Επειδή τα πειράματα ήταν επιτυχή, προχωρήσαμε σε ex vivo πειράματα εγκεφαλικού και ηπατικού ιστού βοοειδούς. Τα αποτελέσματα των ex vivo πειραμάτων της μαγνητικής υπερθερμίας ήταν επίσης επιτυχή και συμφωνούν με υπολογιστικές προσομοιώσεις
description: The aim of the present thesis was the study of magnetic particle hyperthermia in phantom and animal tissues. At first, we examined the thermic efficiency of magnetic nanoparticles in aqueous solutions. The purpose of these experiments was the determination of the optimum concentration and optimum volume of the ferrofluids, which were used for the further experiments. Further, we injected these ferrofluids in phantom tissues from agarose, which were synthesized in the laboratory, in order to apply magnetic hyperthermia. Since the experiments were successful, we examined magnetic hyperthermia ex vivo in bovine brain and liver tissues. The results of the ex vivo experiments were also successful and they are in good agreement with simulations
description: Σε συνεργασία με το Ινστιτούτο Τεχνολογίας Γκρενόμπλ (Γαλλία), το ΕΚΕΦΕ Δημόκριτος, και το CNRS (Centre National de la Researche Scientifique, Γαλλία)
Το κείμενο της Καινής Διαθήκης στους εκκλησιαστικούς συγγραφείς του 2ου αιώνα
Creators: name: Γαϊτάνογλου, Ιωάννης Σάββα
Publisher: name: Aristotle University of Thessaloniki
Year: 2017
Subjects: Κανόνας στην Καινή Διαθήκη
Απολογητές-2ος αιώνας
Ειρηναίος Λουγδούνου
Κλήμης ο Αλεξανδρεύς
Αποστολικοί πατέρες-Κείμενο Κ. Διαθήκης
Canon in New Testament
Apostolic fathers-New Testament text
Clement of Alexandria
Apologists-2nd century
Irenaeus of Lyons

description: Σκοπός της διπλωματικής εργασίας είναι να παρουσιάσει την κατάσταση του κειμένου της Καινής Διαθήκης, αλλά και του κανόνα της στους εκκλησιαστικούς συγγραφείς του 2ου αι. μέσα από τα κείμενα τους. Εξετάσαμε αρχικά το κείμενο της Καινής Διαθήκης στα έργα των Αποστολικών Πατέρων, στη συνέχεια στους Απολογητές και τελευταία στον Ειρηναίο Λυώνος και στον Κλήμεντα τον Αλεξανδρέα. Έπειτα αναφερθήκαμε στις ιδιαιτερότητες που έχει ο εκάστοτε εκκλησιαστικός πατέρας, αναφορικά με τον τρόπο παραπομπής και τη σχέση τους με τα βιβλία της Καινής Διαθήκης. Επιπλέον αναφερθήκαμε στην ιστορία του Κανόνα και στο πως αυτός εξελίσσεται στα εκκλησιαστικά έργα του 2ου αι.
description: The aim of the present thesis was the study of the New Testament Text in the writings of the Church Fathers of the 2nd century. Furthermore, we examined the development of the New Testament Canon. We structured the study in three groups of writers which are the following ones: Apostolic Fathers, Apologists, Irinaios of Lyon and Clemens of Alexandria. Next, we determined the characteristics of each Father concerning their ways of quoting in reference to their relation to the New Testament Books. In addition to this, we studied the development of the New Testament Canon in the 2nd century considering the works of these Church Fathers
MPA Europe Report Deliverable 2.4 Marine ecosystem classification for near seabed waters of Europe
Creators: name: Campoy, Ana N.
name: Assis, Jorge
name: Addamo, Anna Maria
name: Zhao, Qianshuo
name: Costello, Mark John
Publisher: name: Zenodo
Year: 2023

description: Disclaimer: This is document is part of a deliverable not yet approved by the European Commission. The present document details the data acquisition and computational procedures involved in Deliverable 2.4 of MPA Europe. It provides the classification of marine ecosystems in Europe for near seabed waters driven by a wide range of spatially complete and standardised environmental data that reflect both ecosystem conditions and functioning.
End-to-End Spoken Language Understanding for Generalized Voice Assistants
Creators: name: Saxon, Michael
name: Choudhary, Samridhi
name: McKenna, Joseph P.
name: Mouchtaris, Athanasios
Publisher: name: arXiv
Year: 2021
Subjects: subject: Computation and Language (cs.CL)
subject: Artificial Intelligence (cs.AI)
subject: Sound (cs.SD)
subject: Audio and Speech Processing (eess.AS)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: End-to-end (E2E) spoken language understanding (SLU) systems predict utterance semantics directly from speech using a single model. Previous work in this area has focused on targeted tasks in fixed domains, where the output semantic structure is assumed a priori and the input speech is of limited complexity. In this work we present our approach to developing an E2E model for generalized SLU in commercial voice assistants (VAs). We propose a fully differentiable, transformer-based, hierarchical system that can be pretrained at both the ASR and NLU levels. This is then fine-tuned on both transcription and semantic classification losses to handle a diverse set of intent and argument combinations. This leads to an SLU system that achieves significant improvements over baselines on a complex internal generalized VA dataset with a 43% improvement in accuracy, while still meeting the 99% accuracy benchmark on the popular Fluent Speech Commands dataset. We further evaluate our model on a hard test set, exclusively containing slot arguments unseen in training, and demonstrate a nearly 20% improvement, showing the efficacy of our approach in truly demanding VA scenarios.
description: Accepted to Interspeech 2021; 5 pages, 2 tables, 1 figure
Xi and Omega baryons in the Skyrme model
Creators: name: Oh, Yongseok
Publisher: name: arXiv
Year: 2007
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: The mass spectrum and magnetic moments of Ξand Ωbaryon resonances are investigated in the bound state approach of the Skyrme model. The empirical hyperon spectrum shows that several hyperon resonances share a pattern of (approximately) equal mass spacings between the states of same spin but of opposite parity. It is found that this pattern can be explained mostly by the energy difference between the P-wave and S-wave kaons bound to the soliton. Although one cannot exclude the possibility that these states can be described as pion-hyperon resonances, the present approach predicts that Ξ(1620) and Ξ(1690) have J^P = 12^-, while Ξ(1950) has J^P = 12^+. The differences with the quark model predictions for the Ξand Ωbaryon spectrum are pointed out. Several relations for the masses and magnetic moments of those resonances are also obtained.
description: 17 pages, REVTeX, to be published in Phys. Rev. D