cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Lorentz invariant CPT breaking in the Dirac equation
Creators: name: Fujikawa, Kazuo
name: Tureanu, Anca
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: If one modifies the Dirac equation in momentum space to $[γ^μp_μ-m-Δm(θ(p_{0})-θ(-p_{0})) θ(p_μ^{2})]ψ(p)=0$, the symmetry of positive and negative energy eigenvalues is lifted by $m\pm Δm$ for a small $Δm$. The mass degeneracy of the particle and antiparticle is thus lifted in a Lorentz invariant manner since the combinations $θ(\pm p_{0})θ(p_μ^{2})$ with step functions are manifestly Lorentz invariant. We explain an explicit construction of this CPT breaking term in coordinate space, which is Lorentz invariant but non-local at a distance scale of the Planck length. The application of this Lorentz invariant CPT breaking mechanism to the possible mass splitting of the neutrino and antineutrino in the Standard Model is briefly discussed.
description: Talk given at the Memorial Meeting for Abdus Salam's 90th Birthday, Nanyang Technological University, Singapore, January 25-28, 2016 (to appear in the Proceedings)
Nanoscale thermal imaging of dissipation in quantum systems
Creators: name: Halbertal, Dorri
name: Cuppens, Jo
name: Shalom, Moshe Ben
name: Embon, Lior
name: Shadmi, Nitzan
name: Anahory, Yonathan
name: Naren, HR
name: Sarkar, Jayanta
name: Uri, Aviram
name: Ronen, Yuval
name: Myasoedov, Yury
name: Levitov, Leonid
name: Joselevich, Ernesto
name: Geim, Andre Konstantin
name: Zeldov, Eli
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: Superconductivity (cond-mat.supr-con)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: Energy dissipation is a fundamental process governing the dynamics of physical, chemical, and biological systems. It is also one of the main characteristics distinguishing quantum and classical phenomena. In condensed matter physics, in particular, scattering mechanisms, loss of quantum information, or breakdown of topological protection are deeply rooted in the intricate details of how and where the dissipation occurs. Despite its vital importance the microscopic behavior of a system is usually not formulated in terms of dissipation because the latter is not a readily measureable quantity on the microscale. Although nanoscale thermometry is gaining much recent interest, the existing thermal imaging methods lack the necessary sensitivity and are unsuitable for low temperature operation required for study of quantum systems. Here we report a superconducting quantum interference nano-thermometer device with sub 50 nm diameter that resides at the apex of a sharp pipette and provides scanning cryogenic thermal sensing with four orders of magnitude improved thermal sensitivity of below 1 μK/Hz1/2. The non-contact non-invasive thermometry allows thermal imaging of very low nanoscale energy dissipation down to the fundamental Landauer limit of 40 fW for continuous readout of a single qubit at 1 GHz at 4.2 K. These advances enable observation of dissipation due to single electron charging of individual quantum dots in carbon nanotubes and reveal a novel dissipation mechanism due to resonant localized states in hBN encapsulated graphene, opening the door to direct imaging of nanoscale dissipation processes in quantum matter.
description: Submitted to Nature
The NUTs and Bolts of Squashed Holography
Creators: name: Bobev, Nikolay
name: Hertog, Thomas
name: Vreys, Yannick
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We evaluate the partition function of the free O(N) model on a two-parameter family of squashed three spheres. We also find new solutions of general relativity with negative cosmological constant and the same double squashed boundary geometry and analyse their thermodynamic properties. Remarkably, both systems exhibit a qualitatively similar behaviour over the entire configuration space of boundary geometries. Recent formulations of dS/CFT enable one to interpret the field theory partition function as a function of the two squashing parameters as the Hartle-Hawking wave function in a minisuperspace model of anisotropic deformations of de Sitter space. The resulting probability distribution is normalisable and globally peaked at the round three sphere, with a low amplitude of boundary geometries with negative scalar curvature.
description: 41 pages, 19 figures
Low-energy microscopic models for iron-based superconductors: a review
Creators: name: Fernandes, Rafael M.
name: Chubukov, Andrey V.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: The development of sensible microscopic models is essential to elucidate the normal-state and superconducting properties of the iron-based superconductors. Because these materials are mostly metallic, a good starting point is an effective low-energy model that captures the electronic states near the Fermi level and their interactions. However, in contrast to cuprates, iron-based high-$T_{c}$ compounds are multi-orbital systems with Hubbard and Hund interactions, resulting in a rather involved 10-orbital lattice model. Here we review different minimal models that have been proposed to unveil the universal features of these systems. We first review minimal models defined solely in the orbital basis, which focus on a particular subspace of orbitals, or solely in the band basis, which rely only on the geometry of the Fermi surface. The former, while providing important qualitative insight into the role of the orbital degrees of freedom, do not distinguish between high-energy and low-energy sectors and, for this reason, generally do not go beyond mean-field. The latter allow one to go beyond mean-field and investigate the interplay between superconducting and magnetic orders as well as Ising-nematic order. However, they cannot capture orbital-dependent features like spontaneous orbital order. We then review recent proposals for a minimal model that operates in the band basis but fully incorporates the orbital composition and symmetries of the low-energy excitations. We discuss the results of the renormalization group study of such a model, particularly of the interplay between superconductivity, magnetism, and spontaneous orbital order, and compare theoretical predictions with experiments on iron pnictides and chalcogenides. We also discuss the impact of the glide-plane symmetry on the low-energy models, highlighting the key role played by the spin-orbit coupling.
description: Review paper; 39 pages, 24 figures; comments welcome
Two eclipsing ultraluminous X-ray sources in M 51
Creators: name: Urquhart, Ryan
name: Soria, Roberto
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We present the discovery, from archival Chandra and XMM-Newton data, of X-ray eclipses in two ultraluminous X-ray sources (ULXs), located in the same region of the galaxy M 51: CXOM51 J132940.0$+$471237 (ULX-1, for simplicity) and CXOM51 J132939.5$+$471244 (ULX-2). Three eclipses were detected for ULX-1, two for ULX-2. The presence of eclipses puts strong constraints on the viewing angle, suggesting that both ULXs are seen almost edge-on and are certainly not beamed towards us. Despite the similar viewing angles and luminosities ($L_{\rm X} \approx 2 \times 10^{39}$ erg s$^{-1}$ in the $0.3$-$8$ keV band for both sources), their X-ray properties are different. ULX-1 has a soft spectrum, well fitted by Comptonization emission from a medium with electron temperature $kT_e \approx 1$ keV. ULX-2 is harder, well fitted by a slim disk with $kT_{\rm in} \approx 1.5$-$1.8$ keV and normalization consistent with a $\sim 10 M_{\odot}$ black hole. ULX-1 has a significant contribution from multi-temperature thermal plasma emission ($L_{\rm X,mekal} \approx 2 \times 10^{38}$ erg s$^{-1}$); about $10$% of this emission remains visible during the eclipses, proving that the emitting gas comes from a region slightly more extended than the size of the donor star. From the sequence and duration of the Chandra observations in and out of eclipse, we constrain the binary period of ULX-1 to be either $\approx 6.3$ days, or $\approx 12.5-13$ days. If the donor star fills its Roche lobe (a plausible assumption for ULXs), both cases require an evolved donor; most likely a blue supergiant, given the young age of the stellar population in that galactic environment.
description: 24 pages, 19 figures, 13 tables, accepted for publication in ApJ
The Evolution of Star Formation Activity in Cluster Galaxies Over $0.15
Creators: name: Wagner, Cory R.
name: Courteau, Stephane
name: Brodwin, Mark
name: Stanford, S. A.
name: Snyder, Gregory F.
name: Stern, Daniel
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We explore 7.5 billion years of evolution in the star formation activity of massive ($M_{\star}>10^{10.1}\,M_{\odot}$) cluster galaxies using a sample of 25 clusters over $0.15
description: 18 pages, 11 figures. Accepted for publication in The Astrophysical Journal
Electromagnetically Induced Transparency and Quantum Heat Engines
Creators: name: Harris, S. E.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We describe how electromagnetically induced transparency may be used to construct a non-traditional near-ideal quantum heat engine as constrained by the Second Law. The engine is pumped by a thermal reservoir that may be either hotter or colder than that of an exhaust reservoir, and also by a monochromatic laser. As output, it produces a bright narrow emission at line center of an otherwise absorbing transition.
Towards Learning and Verifying Invariants of Cyber-Physical Systems by Code Mutation
Creators: name: Chen, Yuqi
name: Poskitt, Christopher M.
name: Sun, Jun
Publisher: name: arXiv
Year: 2016
Subjects: subject: Software Engineering (cs.SE)
subject: Machine Learning (cs.LG)
subject: Logic in Computer Science (cs.LO)
subject: FOS: Computer and information sciences

description: Cyber-physical systems (CPS), which integrate algorithmic control with physical processes, often consist of physically distributed components communicating over a network. A malfunctioning or compromised component in such a CPS can lead to costly consequences, especially in the context of public infrastructure. In this short paper, we argue for the importance of constructing invariants (or models) of the physical behaviour exhibited by CPS, motivated by their applications to the control, monitoring, and attestation of components. To achieve this despite the inherent complexity of CPS, we propose a new technique for learning invariants that combines machine learning with ideas from mutation testing. We present a preliminary study on a water treatment system that suggests the efficacy of this approach, propose strategies for establishing confidence in the correctness of invariants, then summarise some research questions and the steps we are taking to investigate them.
description: Short paper accepted by the 21st International Symposium on Formal Methods (FM 2016)
Degeneracy-preserving quantum non-demolition measurement of parity-type observables for cat-qubits
Creators: name: Cohen, Joachim
name: Smith, W. Clarke
name: Devoret, Michel H.
name: Mirrahimi, Mazyar
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: A central requirement for any quantum error correction scheme is the ability to perform quantum non-demolition measurements of an error syndrome, corresponding to a special symmetry property of the encoding scheme. It is in particular important that such a measurement does not introduce extra error mechanisms, not included in the error model of the correction scheme. In this letter, we ensure such a robustness by designing an interaction with a measurement device that preserves the degeneracy of the measured observable. More precisely, we propose a scheme to perform continuous and quantum non-demolition measurement of photon-number parity in a microwave cavity. This corresponds to the error syndrome in a class of error correcting codes called the cat-codes, which have recently proven to be efficient and versatile for quantum information processing. In our design, we exploit the strongly nonlinear Hamiltonian of a high-impedance Josephson circuit, coupling a high-Q cavity storage cavity mode to a low-Q readout one. By driving the readout resonator at its resonance, the phase of the reflected/transmitted signal carries directly exploitable information on parity-type observables for encoded cat-qubits of the high-Q mode.
description: 25 pages, 7 figures
Fracture of granular materials composed of arbitrary grain shapes: A new cohesive interaction model
Creators: name: Neveu, A
name: Artoni, R
name: Richard, P
name: Descantes, Y
Publisher: name: arXiv
Year: 2016
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: Discrete Element Methods (DEM) are a useful tool to model the fracture of cohesive granular materials. For this kind of application, simple particle shapes (discs in 2D, spheres in 3D) are usually employed. However, dealing with more general particle shapes allows to account for the natural heterogeneity of grains inside real materials. We present a discrete model allowing to mimic cohesion between contacting or non-contacting particles whatever their shape in 2D and 3D. The cohesive interactions are made of cohesion points placed on interacting particles, with the aim of representing a cohesive phase lying between the grains. Contact situations are solved according to unilateral contact and Coulomb friction laws. In order to test the developed model, 2D unixial compression simulations are performed. Numerical results show the ability of the model to mimic the macroscopic behavior of an aggregate grain subject to axial compression, as well as fracture initiation and propagation. A study of the influence of model and sample parameters provides important information on the ability of the model to reproduce various behaviors.
Doctoral thesis recital (piano)
Creators: name: Li, Xinyi
Publisher: name: The University of Texas at Austin
Year: 2023
Subjects: Sonatas (Piano)
Piano music
Rhapsodies (Music)

description: Sonata no. 3 op. 58 in B minor / Frederic Chopin -- Sonata no. 5, op. 10 no. 1, in C minor / Ludwig van Beethoven -- Hungarian rhapsody no.12 / Franz Liszt.
Creation and characterization of He-related color centers in diamond
Creators: name: Forneris, Jacopo
name: Tengattini, Andrea
name: Tchernij, Sviatoslav Ditalia
name: Picollo, Federico
name: Battiato, Alfio
name: Traina, Paolo
name: Degiovanni, Ivo
name: Moreva, Ekaterina
name: Brida, Giorgio
name: Grilj, Veljko
name: Skukan, Natko
name: Jakšić, Milko
name: Genovese, Marco
name: Olivero, Paolo
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: Diamond is a promising material for the development of emerging applications in quantum optics, quantum information and quantum sensing. The fabrication and characterization of novel luminescent defects with suitable opto-physical properties is therefore of primary importance for further advances in these research fields. In this work we report on the investigation in the formation of photoluminescent (PL) defects upon MeV He implantation in diamond. Such color centers, previously reported only in electroluminescence and cathodoluminescence regime, exhibited two sharp emission lines at 536.5 nm and 560.5 nm, without significant phonon sidebands. A strong correlation between the PL intensities of the above-mentioned emission lines and the He implantation fluence was found in the 10^15-10^17 cm^{-2} fluence range. The PL emission features were not detected in control samples, i.e. samples that were either unirradiated or irradiated with different ion species (H, C). Moreover, the PL emission lines disappeared in samples that were He-implanted above the graphitization threshold. Therefore, the PL features are attributed to optically active defects in the diamond matrix associated with He impurities. The intensity of the 536.5 nm and 560.5 nm emission lines was investigated as a function of the annealing temperature of the diamond substrate. The emission was observed upon annealing at temperatures higher than 500°C, at the expenses of the concurrently decreasing neutral-vacancy-related GR1 emission intensity. Therefore, our findings indicate that the luminescence originates from the formation of a stable lattice defect. Finally, the emission was investigated under different laser excitations wavelengths (i.e. 532 nm and 405 nm) with the purpose of gaining a preliminary insight about the position of the related levels in the energy gap of diamond.
Harnessing Poly(ionic liquid)s for Sensing Applications
Creators: name: Guterman, Ryan
name: Ambrogi, Martina
name: Yuan, Jiayin
Publisher: name: arXiv
Year: 2016
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The interest in poly(ionic liquids) for sensing applications are derived from their strong interactions to a variety of analytes. By combining the desirable mechanical properties of polymers with the physical and chemical properties of ILs, new materials can be created. The tunable nature of both ionic liquids and polymers allows for incredible diversity, which is exemplified in their broad applicability. In this article we examine the new field of poly(ionic liquid) sensors by providing a detailed look at the current state-of-the-art sensing devices for solvents, gasses, biomolecules, pH, and anions.
description: 28 pages, 8 figures
System level analysis of heterogeneous networks under imperfect traffic hotspot localization
Creators: name: Jaziri, Aymen
name: Nasri, Ridha
name: Chahed, Tijani
Publisher: name: arXiv
Year: 2016
Subjects: subject: Networking and Internet Architecture (cs.NI)
subject: FOS: Computer and information sciences

description: We study, in this paper, the impact of imperfect small cell positioning with respect to traffic hotspots in cellular networks. In order to derive the throughput distribution in macro and small cells, we firstly perform static level analysis of the system considering a non-uniform distribution of user locations. We secondly introduce the dynamics of the system, characterized by random arrivals and departures of users after a finite service duration, with the service rates and distribution of radio conditions outfitted from the first part of the work. When dealing with the dynamics of the system, macro and small cells are modeled by multi-class processor sharing queues. Macro and small cells are assumed to be operating in the same bandwidth. Consequently, they are coupled due to the mutual interferences generated by each cell to the other. We derive several performance metrics such as the mean flow throughput and the gain, if any, generated from deploying small cells to manage traffic hotspots. Our results show that in case the hotspot is near the macro BS (Base Station), even a perfect positioning of the small cell will not yield improved performance due to the high interference experienced at macro and small cell users. However, in case the hotspot is located far enough from the macro BS, performing errors in small cell positioning is tolerated (since related results show positive gains) and it is still beneficial in offloading traffic from the congested macrocell. The best performance metrics depend also on several other important factors such as the users' arrival intensity, the capacity of the cell and the size of the traffic hotspot.
description: This paper is already published in IEEE Transactions on Vehicular Technology 2016
Bayesian Cosmic Web Reconstruction: BARCODE for Clusters
Creators: name: Bos, E. G. Patrick
name: van de Weygaert, Rien
name: Kitaura, Francisco
name: Cautun, Marius
Publisher: name: arXiv
Year: 2016
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We describe the Bayesian BARCODE formalism that has been designed towards the reconstruction of the Cosmic Web in a given volume on the basis of the sampled galaxy cluster distribution. Based on the realization that the massive compact clusters are responsible for the major share of the large scale tidal force field shaping the anisotropic and in particular filamentary features in the Cosmic Web. Given the nonlinearity of the constraints imposed by the cluster configurations, we resort to a state-of-the-art constrained reconstruction technique to find a proper statistically sampled realization of the original initial density and velocity field in the same cosmic region. Ultimately, the subsequent gravitational evolution of these initial conditions towards the implied Cosmic Web configuration can be followed on the basis of a proper analytical model or an N-body computer simulation. The BARCODE formalism includes an implicit treatment for redshift space distortions. This enables a direct reconstruction on the basis of observational data, without the need for a correction of redshift space artifacts. In this contribution we provide a general overview of the the Cosmic Web connection with clusters and a description of the Bayesian BARCODE formalism. We conclude with a presentation of its successful workings with respect to test runs based on a simulated large scale matter distribution, in physical space as well as in redshift space.
description: 18 pages, 8 figures, Proceedings of IAU Symposium 308 "The Zeldovich Universe: Genesis and Growth of the Cosmic Web", 23-28 June 2014, Tallinn, Estonia
Subfemtonewton Force Spectroscopy at the Thermal Limit in Liquids
Creators: name: Liu, Lulu
name: Kheifets, Simon
name: Ginis, Vincent
name: Capasso, Federico
Publisher: name: arXiv
Year: 2016
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We demonstrate thermally limited force spectroscopy using a probe formed by a dielectric microsphere optically trapped in water near a dielectric surface. We achieve force resolution below 1 fN in 100 s, corresponding to a 2 Å rms displacement of the probe. Our measurement combines a calibrated evanescent wave particle tracking technique and a lock-in detection method. We demonstrate the accuracy of our method by measurement of the height-dependent force exerted on the probe by an evanescent wave, the results of which are in agreement with Mie theory calculations.
description: 5 pages; 4 figures
Trochoidal trajectories of self-propelled Janus particles in a diverging laser beam
Creators: name: Moyses, Henrique
name: Palacci, Jeremie
name: Sacanna, Stefano
name: Grier, David G.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We describe colloidal Janus particles with metallic and dielectric faces that swim vigorously when illuminated by defocused optical tweezers without consuming any chemical fuel. Rather than wandering randomly, these optically-activated colloidal swimmers circulate back and forth through the beam of light, tracing out sinuous rosette patterns. We propose a model for this mode of light-activated transport that accounts for the observed behavior through a combination of self-thermophoresis and optically-induced torque. In the deterministic limit, this model yields trajectories that resemble rosette curves known as hypotrochoids.
description: 9 pages, 7 figures; cover article
Gravitational waveforms in scalar-tensor gravity at 2PN relative order
Creators: name: Sennett, Noah
name: Marsat, Sylvain
name: Buonanno, Alessandra
Publisher: name: arXiv
Year: 2016
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We compute the gravitational waveform from a binary system in scalar-tensor gravity at 2PN relative order. We restrict our calculation to non-spinning binary systems on quasi-circular orbits and compute the spin-weighted spherical modes of the radiation. The evolution of the phase of the waveform is computed in the time and frequency domains. The emission of dipolar radiation is the lowest-order dissipative process in scalar-tensor gravity. However, stringent constraints set by current astrophysical observations indicate that this effect is subdominant to quadrupolar radiation for most prospective gravitational-wave sources. We compute the waveform for systems whose inspiral is driven by: (a) dipolar radiation (e.g., binary pulsars or spontaneously scalarized systems) and (b) quadrupolar radiation (e.g., typical sources for space-based and ground-based detectors).
description: 23 pages
Optical flare activity in the low-mass eclipsing binary GJ~3236
Creators: name: Parimucha, S.
name: Dubovsky, P.
name: Vanko, M.
name: Cokina, M.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We present our observations of the low-mass eclipsing binary GJ~3236. We have analyzed a phased $R_C$ light-curve and confirmed previously determined fundamental parameters of the components. We detected evolution of the spot(s) and found that there exists a large spot near a polar region of the primary component and another spot either on the primary or the secondary component. We also observed 7 flare events and determined a flare rate of about 0.1 flares per hour. We observed two high energy, long-term flares with a complex light curve and possibly four weak short-term flaring events. A majority of the flares was detected in the $R_C$ filter, which indicate their high energy.
description: 7 pages, 6 figures, accepted to ApSS
Factorization in mixed norm Hardy and BMO spaces
Creators: name: Lechner, Richard
Publisher: name: arXiv
Year: 2016
Subjects: subject: Functional Analysis (math.FA)
subject: FOS: Mathematics
subject: 46B25, 46B07, 46B26, 30H35, 30H10

description: Let $1\leq p,q < \infty$ and $1\leq r \leq \infty$. We show that the direct sum of mixed norm Hardy spaces $\big(\sum_n H^p_n(H^q_n)\big)_r$ and the sum of their dual spaces $\big(\sum_n H^p_n(H^q_n)^*\big)_r$ are both primary. We do so by using Bourgain's localization method and solving the finite dimensional factorization problem. In particular, we obtain that the spaces $\big(\sum_{n\in \mathbb N} H_n^1(H_n^s)\big)_r$, $\big(\sum_{n\in \mathbb N} H_n^s(H_n^1)\big)_r$, as well as $\big(\sum_{n\in \mathbb N} BMO_n(H_n^s)\big)_r$ and $\big(\sum_{n\in \mathbb N} H^s_n(BMO_n)\big)_r$, $1 < s < \infty$, $1\leq r \leq \infty$, are all primary.
description: 29 pages, 8 figures
The Zeldovich & Adhesion approximations, and applications to the local universe
Creators: name: Hidding, Johan
name: van de Weygaert, Rien
name: Shandarin, Sergei
Publisher: name: arXiv
Year: 2016
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: The Zeldovich approximation (ZA) predicts the formation of a web of singularities. While these singularities may only exist in the most formal interpretation of the ZA, they provide a powerful tool for the analysis of initial conditions. We present a novel method to find the skeleton of the resulting cosmic web based on singularities in the primordial deformation tensor and its higher order derivatives. We show that the A_3-lines predict the formation of filaments in a two-dimensional model. We continue with applications of the adhesion model to visualise structures in the local (z < 0.03) universe.
description: 9 pages, 8 figures, Proceedings of IAU Symposium 308 "The Zeldovich Universe: Genesis and Growth of the Cosmic Web", 23-28 June 2014, Tallinn, Estonia
The Vorticity of Solar Photospheric Flows on the Scale of Granulation
Creators: name: Pevtsov, A. A.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We employ time sequences of images observed with a G-band filter (4305Å) by the Solar Optical Telescope (SOT) on board of Hinode spacecraft at different latitude along solar central me-ridian to study vorticity of granular flows in quiet Sun areas during deep minimum of solar activity. Using a feature correlation tracking (FCT) technique, we calculate the vorticity of granular-scale flows. Assuming the known pattern of vertical flows (upward in granules and downward in inter-granular lanes), we infer the sign of kinetic helicity of these flows. We show that the kinetic helicity of granular flows and intergranular vortices exhibits a weak hemispheric preference, which is in agreement with the action of the Coriolis force. This slight hemispheric sign asymmetry, however, is not statistically significant given large scatter in the average vorticity. The sign of the current he-licity density of network magnetic fields computed using full disk vector magnetograms from the Synoptic Optical Long-term Investigations of the Sun (SOLIS) does not show any hemispheric preference. The combination of these two findings suggests that the photospheric dynamo operating on the scale of granular flows is non-helical in nature.
description: 11 pages, 5 figures, in press Geomagnetism and Aeronomy
Fluorinated surfaces: towards a universal matrix-free substrates for Laser Desorption Ionization
Creators: name: Piotto, Chiara
name: Guella, Graziano
name: Bettotti, Paolo
Publisher: name: arXiv
Year: 2016
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Matrix Assisted Laser Desorption Ionization (MALDI) is a soft ionization method that finds widespread applications in high-throughput mass spectrometric analysis. One of the main limit of this technique is that it requires the use of matrices: these molecules enable the analytes desorption and ionization (D/I) processes but also generate strong interfering signals in the low mass spectral region, preventing a suitable detection of low molecular weight compounds. The possibility to avoid their use will ease both sample preparation and mass spectrum (MS) interpretation. In recent years nanostructured surfaces have been proposed as a viable method to achieve such goal but the results are limited to specific classes of chemical compounds and the approach lacks in generality. Here we demonstrate that the fluorination of surfaces is the only step needed to activate the target and to achieve matrix-free operation with the same detection limit obtained using nanostructured chips. The results of this work suggest that D/I is a purely interfacial effect, with negligible contribution from chemical nature of the underlying substrate, provided that the substrate is conductive and able to efficiently absorb the UV laser beam.
A Broadband Emission Model of Magnetar Wind Nebulae
Creators: name: Tanaka, Shuta J.
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Angular momentum loss by the plasma wind is considered as a universal feature of isolated neutron stars including magnetars. The wind nebulae powered by magnetars allow us to compare the wind properties and the spin-evolution of magnetars with those of rotation-powered pulsars (RPPs). In this paper, we construct a broadband emission model of magnetar wind nebulae (MWNe). The model is similar to past studies of young pulsar wind nebulae (PWNe) around RPPs, but is modified for the application to MWNe that have far less observational information than the young PWNe. We apply the model to the MWN around the youngest ($\sim$ 1kyr) magnetar 1E 1547.0-5408 that has the largest spin-down power $L_{\rm spin}$ among all the magnetars. However, the MWN is faint because of low $L_{\rm spin}$ of 1E 1547.0-5408 compared with the young RPPs. Since most of parameters are not well constrained only by an X-ray flux upper limit of the MWN, we adopt the model parameters from young PWN Kes 75 around PSR J1846-0258 that is a peculiar RPP showing magnetar-like behaviors. The model predicts $γ$-ray flux that will be detected in a future TeV $γ$-ray observation by {\it CTA}. The MWN spectrum does not allow us to test hypothesis that 1E 1547.0-5408 had milliseconds period at its birth because the particles injected early phase of evolution are suffered from severe adiabatic and synchrotron losses. Further both observational and theoretical studies of the wind nebulae around magnetars are required to constrain the wind and spin-down properties of magnetars.
description: Accepted for publication in ApJ, 27 pages, 3 figures
Depth Estimation Through a Generative Model of Light Field Synthesis
Creators: name: Sajjadi, Mehdi S. M.
name: Köhler, Rolf
name: Schölkopf, Bernhard
name: Hirsch, Michael
Publisher: name: arXiv
Year: 2016
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Graphics (cs.GR)
subject: FOS: Computer and information sciences

description: Light field photography captures rich structural information that may facilitate a number of traditional image processing and computer vision tasks. A crucial ingredient in such endeavors is accurate depth recovery. We present a novel framework that allows the recovery of a high quality continuous depth map from light field data. To this end we propose a generative model of a light field that is fully parametrized by its corresponding depth map. The model allows for the integration of powerful regularization techniques such as a non-local means prior, facilitating accurate depth map estimation.
description: German Conference on Pattern Recognition (GCPR) 2016
Examining and contrasting the cognitive activities engaged in undergraduate research experiences and lab courses
Creators: name: Holmes, N. G.
name: Wieman, Carl E.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Physics Education (physics.ed-ph)
subject: FOS: Physical sciences

description: While the positive outcomes of undergraduate research experiences (UREs) have been extensively categorized, the mechanisms for those outcomes are less understood. Through lightly structured focus group interviews, we have extracted the cognitive tasks that students identify as engaging in during their UREs. We also use their many comparative statements about their coursework, especially lab courses, to evaluate their experimental physics-related cognitive tasks in those environments. We find there are a number of cognitive tasks consistently encountered in physics UREs that are present in most experimental research. These are seldom encountered in lab or lecture courses, with some notable exceptions. Having time to reflect and fix or revise, and having a sense of autonomy, were both repeatedly cited as key enablers of the benefits of UREs. We also identify tasks encountered in actual experimental research that are not encountered in UREs. We use these findings to identify opportunities for better integration of the cognitive tasks in UREs and lab courses, as well as discussing the barriers that exist. This work responds to extensive calls for science education to better develop students' scientific skills and practices, as well as calls to expose more students to scientific research.
description: 11 pages, 3 figures
The Physics of Biofilms -- An Introduction
Creators: name: Mazza, Marco G.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Biological Physics (physics.bio-ph)
subject: Soft Condensed Matter (cond-mat.soft)
subject: Cell Behavior (q-bio.CB)
subject: FOS: Physical sciences
subject: FOS: Biological sciences

description: Biofilms are complex, self-organized consortia of microorganisms that produce a functional, protective matrix of biomolecules. Physically, the structure of a biofilm can be described as an entangled polymer network which grows and changes under the effect of gradients of nutrients, cell differentiation, quorum sensing, bacterial motion, and interaction with the environment. Its development is complex, and constantly adapting to environmental stimuli. Here, we review the fundamental physical processes the govern the inception, growth and development of a biofilm. Two important mechanisms guide the initial phase in a biofilm life cycle: (\emph{i}) the cell motility near or at a solid interface, and (\emph{ii}) the cellular adhesion. Both processes are crucial for initiating the colony and for ensuring its stability. A mature biofilm behaves as a viscoelastic fluid with a complex, history-dependent dynamics. We discuss progress and challenges in the determination of its physical properties. Experimental and theoretical methods are now available that aim at integrating the biofilm's hierarchy of interactions, and the heterogeneity of composition and spatial structures. We also discuss important directions in which future work should be directed.
Magnonic Weyl semimetal in pyrochlore ferromagnets
Creators: name: Su, Ying
name: Wang, X. S.
name: Wang, X. R.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Topological states of matter have been a subject of intensive studies in recent years because of their exotic properties such as the topologically protected edge and surface states. The initial studies were exclusively for electron systems. It is now known that topological states can also exist for other particles. Indeed, topologically protected edge states have already been found for phonons and photons. In spite of active searching for topological states in many fields, the studies in magnetism are relatively rare although topological states are apparently important and useful in magnonics. Here we show that the pyrochlore ferromagnets with the Dzyaloshinskii-Moriya interaction are intrinsic magnonic Weyl semimetals. Similar to the electronic Weyl semimetals, the magnon bands in a magnonic Weyl semimetal are nontrivially crossing in pairs at special points (called Weyl nodes) in momentum space. The equal energy contour around the Weyl nodes gives rise to the Fermi arcs on sample surfaces due to the topologically protected surface states between each pair of Weyl nodes. Additional Weyl nodes and Fermi arcs can be generated in lower energy magnon bands when an anisotropic exchange interaction is introduced.
description: 7 pages, 3 figures
Stability of the d-wave pairing with respect to the intersite Coulomb repulsion in cuprate superconductors
Creators: name: Val'kov, V. V.
name: Dzebisashvili, D. M.
name: Korovushkin, M. M.
name: Barabanov, A. F.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: Within the spin-fermion model for cuprate superconductors, the influence of the intersite Coulomb interactions $V_2$ and $V_2'$ between holes located at the next-nearest-neighbor oxygen ions of CuO$_2$ plane on the implementation of the d_{x^2-y^2}-wave pairing is studied. It is shown that d-wave pairing can be suppressed only for unphysically large values of $V_2$ and $V_2'$.
description: 5 pages, 2 figures
Revolutionizing our View of Protostellar Multiplicity and Disks: The VLA Nascent Disk and Multiplicity (VANDAM) Survey of the Perseus Molecular Cloud
Creators: name: Tobin, John J.
name: Looney, Leslie W.
name: Li, Zhi-Yun
name: Chandler, Claire J.
name: Dunham, Michael M.
name: Segura-Cox, Dominique
name: Cox, Erin G.
name: Harris, Robert J.
name: Melis, Carl
name: Sadavoy, Sarah I.
name: Pérez, Laura
name: Kratter, Kaitlin
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: There is substantial evidence for disk formation taking place during the early stages of star formation and for most stars being born in multiple systems; however, protostellar multiplicity and disk searches have been hampered by low resolution, sample bias, and variable sensitivity. We have conducted an unbiased, high-sensitivity Karl G. Jansky Very Large Array (VLA) survey toward all known protostars (n = 94) in the Perseus molecular cloud (d~230 pc), with a resolution of ~15 AU (0.06") at 8 mm. We have detected candidate protostellar disks toward 17 sources (with 12 of those in the Class 0 stage) and we have found substructure on < 50AU scales for three Class 0 disk candidates, possibly evidence for disk fragmentation. We have discovered 16 new multiple systems (or new components) in this survey; the new systems have separations < 500 AU and 3 by < 30 AU. We also found a bi-modal distribution of separations, with peaks at ~75 AU and ~3000 AU, suggestive of formation through two distinct mechanisms: disk and turbulent fragmentation. The results from this survey demonstrate the necessity and utility of uniform, unbiased surveys of protostellar systems at millimeter and centimeter wavelengths.
description: Proceedings for 2015 Zermatt ISM Symposium: Conditions and Impact of Star Formation; 4 pages, 3 Figures
Performance Analysis of Small Cells' Deployment under Imperfect Traffic Hotspot Localization
Creators: name: Jaziri, Aymen
name: Nasri, Ridha
name: Chahed, Tijani
Publisher: name: arXiv
Year: 2016
Subjects: subject: Networking and Internet Architecture (cs.NI)
subject: FOS: Computer and information sciences

description: Heterogeneous Networks (HetNets), long been considered in operators' roadmaps for macrocells' network improvements, still continue to attract interest for 5G network deployments. Understanding the efficiency of small cell deployment in the presence of traffic hotspots can further draw operators' attention to this feature. In this context, we evaluate the impact of imperfect small cell positioning on the network performances. We show that the latter is mainly impacted by the position of the hotspot within the cell: in case the hotspot is near the macrocell, even a perfect positioning of the small cell will not yield improved performance due to the interference coming from the macrocell. In the case where the hotspot is located far enough from the macrocell, even a large error in small cell positioning would still be beneficial in offloading traffic from the congested macrocell.
description: This article is already published in IEEE Global Communications Conference (GLOBECOM) 2015
Molecular Gas Kinematics and Line Diagnostics in Early-type Galaxies: NGC4710 and NGC5866
Creators: name: Topal, Selcuk
name: Bureau, Martin
name: Davis, Timothy A.
name: Krips, Melanie
name: Young, Lisa M.
name: Crocker, Alison F.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present interferometric observations of CO lines (12CO(1-0, 2-1) and 13CO(1-0, 2-1)) and dense gas tracers (HCN(1-0), HCO+(1-0), HNC(1-0) and HNCO(4-3)) in two nearby edge-on barred lenticular galaxies, NGC 4710 and NGC 5866, with most of the gas concentrated in a nuclear disc and an inner ring in each galaxy. We probe the physical conditions of a two-component molecular interstellar medium in each galaxy and each kinematic component by using molecular line ratio diagnostics in three complementary ways. First, we measure the ratios of the position-velocity diagrams of different lines, second we measure the ratios of each kinematic component's integrated line intensities as a function of projected position, and third we model these line ratios using a non-local thermodynamic equilibrium radiative transfer code. Overall, the nuclear discs appear to have a tenuous molecular gas component that is hotter, optically thinner and with a larger dense gas fraction than that in the inner rings, suggesting more dense clumps immersed in a hotter more diffuse molecular medium. This is consistent with evidence that the physical conditions in the nuclear discs are similar to those in photo-dissociation regions. A similar picture emerges when comparing the observed molecular line ratios with those of other galaxy types. The physical conditions of the molecular gas in the nuclear discs of NGC4710 and NGC5866 thus appear intermediate between those of spiral galaxies and starbursts, while the star formation in their inner rings is even milder.
description: Accepted for publication in MNRAS, 34 pages, 21 figures, 7 tables
Experimental Characterization of In Vivo Wireless Communication Channels
Creators: name: Demir, A. Fatih
name: Abbasi, Qammer H.
name: Ankarali, Z. Esat
name: Qaraqe, Marwa
name: Serpedin, Erchin
name: Arslan, Huseyin
Publisher: name: arXiv
Year: 2016
Subjects: subject: Other Computer Science (cs.OH)
subject: FOS: Computer and information sciences

description: In vivo wireless medical devices have a critical role in healthcare technologies due to their continuous health monitoring and noninvasive surgery capabilities. In order to fully exploit the potential of such devices, it is necessary to characterize the in vivo wireless communication channel which will help to build reliable and high-performance communication systems. This paper presents preliminary results of experimental characterization for this fascinating communications medium on a human cadaver and compares the results with numerical studies.
description: 2015 IEEE 82nd Vehicular Technology Conference: VTC2015-Fall
Scalable synchronization of spin-Hall oscillators in out-of-plane field
Creators: name: Puliafito, Vito
name: Giordano, Anna
name: Laudani, Antonino
name: Garescì, Francesca
name: Carpentieri, Mario
name: Azzerboni, Bruno
name: Finocchio, Giovanni
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: A strategy for a scalable synchronization of an array of spin-Hall oscillators (SHOs) is illustrated. In detail, we present micromagnetic simulations of two and five SHOs realized by means of couples of triangular golden contacts on the top of a Pt/CoFeB/Ta trilayer. Results highlight that the synchronization occurs for the whole current region that gives rise to the excitation of self-oscillations. This is linked to the role of the magnetodipolar coupling, which is the phenomenon driving the synchronization when the distance between oscillators is not too large. Synchronization turns out to be also robust against geometrical differences of the contacts, simulated by considering variable distances between the tips ranging from 100nm to 200nm. Besides, it entails an enlargement of the radiation pattern that can be useful for the generation of spin-waves in magnonics applications. Simulations performed to study the effect of the interfacial Dzyaloshinskii-Moriya interaction show nonreciprocity in spatial propagation of the synchronized spin-wave. The simplicity of the geometry and the robustness of the achieved synchronization make this design of array of SHOs scalable for a larger number of synchronized oscillators.