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Holonomic approximation through convex integration
http://hdl.handle.net/10993/48418
Title: Holonomic approximation through convex integration
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<br/>Author, co-author: Massot, Patrick; Theilliere, Mélanie
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<br/>Abstract: Convex integration and the holonomic approximation theorem are two well-known pillars of flexibility in differential topology and geometry. They may each seem to have their own flavor and scope. The goal of this paper is to bring some new perspective on this topic. We explain how to prove the holonomic approximation theorem for first order jets using convex integration. More precisely we first prove that this theorem can easily be reduced to proving flexibility of some specific relation. Then we prove this relation is open and ample, hence its flexibility follows from off-the-shelf convex integration.Magnetic small-angle neutron scattering - a powerful probe of the magnetization configuration
http://hdl.handle.net/10993/48400
Title: Magnetic small-angle neutron scattering - a powerful probe of the magnetization configuration
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<br/>Author, co-author: Bersweiler, Mathias; Michels, AndreasObservation of surface magnons and crystalline electric field shifts in superantiferromagnetic NdCu2 nanoparticles
http://hdl.handle.net/10993/48395
Title: Observation of surface magnons and crystalline electric field shifts in superantiferromagnetic NdCu2 nanoparticles
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<br/>Author, co-author: Jefremovas, E. M.; de la Fuente Rodríguez, M.; Damay, F.; Fak, B.; Michels, Andreas; Blanco, J. A.; Barquín, L. F.ENHANCEMENT OF VEGETABLE OIL FUNCTIONALITY FOR RUBBER-COMPOSITE PROCESSING AND PROPERTIES
http://hdl.handle.net/10993/48353
Title: ENHANCEMENT OF VEGETABLE OIL FUNCTIONALITY FOR RUBBER-COMPOSITE PROCESSING AND PROPERTIES
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<br/>Author, co-author: Datta Sarma, ArpanNonstandard n-distances based on certain geometric constructions
http://hdl.handle.net/10993/48339
Title: Nonstandard n-distances based on certain geometric constructions
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<br/>Author, co-author: Kiss, Gergely; Marichal, Jean-Luc
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<br/>Abstract: The concept of n-distance was recently introduced to generalize the classical definition of distance to functions of n arguments. In this paper we investigate this concept through a number of examples based on certain geometrical constructions. In particular, our study shows to which extent the computation of the best constant associated with an n-distance may sometimes be difficult and tricky. It also reveals that two important graph theoretical concepts, namely the total length of the Euclidean Steiner tree and the total length of the minimal spanning tree constructed on n points, are instances of n-distances.Bismut-Stroock Hessian formulas and local Hessian estimates for heat semigroups and harmonic functions on Riemannian manifolds
http://hdl.handle.net/10993/48323
Title: Bismut-Stroock Hessian formulas and local Hessian estimates for heat semigroups and harmonic functions on Riemannian manifolds
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<br/>Author, co-author: Chen, Qin-Qian; Cheng, Li-Juan; Thalmaier, Anton
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<br/>Abstract: In this article, we develop a martingale approach to localized Bismut-type Hessian formulas for heat semigroups on Riemannian manifolds. Our approach extends the Hessian formulas established by
Stroock (1996) and removes in particular the compact manifold restriction. To demonstrate the potential of these formulas, we give as application explicit quantitative local estimates for the Hessian of the heat semigroup, as well as for harmonic functions on regular domains in Riemannian manifolds.Advanced Characterizations of Silica Surface in Rubber Compounds by Solid-State Nuclear Magnetic Resonance Spectroscopy
http://hdl.handle.net/10993/48313
Title: Advanced Characterizations of Silica Surface in Rubber Compounds by Solid-State Nuclear Magnetic Resonance Spectroscopy
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<br/>Author, co-author: Yan, Chuanyu
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<br/>Abstract: This thesis details the development, validation, and application of advanced solid-state nuclear Magnetic resonance spectroscopy (NMR) techniques for the characterization of the silica surface in raw materials and in rubber compounds. The performance of the quantitative techniques (29Si DP-CPMG, SVD and 29Si multiCP) and qualitative techniques (29Si CP-CPMG and {1H-29Si}-1H MCPi) are investigated using model and close-to-real life samples. The insights gained from this study are useful for the surface-specific characterization of silica and could offer clues for similar topics.Quantum transport in topological condensed matter systems
http://hdl.handle.net/10993/48255
Title: Quantum transport in topological condensed matter systems
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<br/>Author, co-author: Ekström, Carl Johan Ingvar
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<br/>Abstract: Topology in condensed matter physics is a field that has exploded in the last two decades. With the realization of its importance, some previously unexplained observations can now be explained. With the progress of time, many new topological phases of matter have been discovered, and topological materials have been shown to be fairly common in nature. Topological materials have further been shown to have properties that may be extremely useful for new technologies, such as spintronics and fault-tolerant quantum computation. The field is however, still evolving, and many properties of these materials are still unknown. In this thesis, we investigate how some of these types of materials react to applied external fields and the theories that can explain these observations.
First, we investigate systems of coupled Majorana bound states. More specifically, we focus on the transport properties of the Majorana box and the T-junction in the presence of charging effects, overlap between the Majorana bound states, and multiple terminals connected to the system. To obtain the transport properties, we apply a master equation and calculate the current through the systems as biases are applied to the different terminals. By tuning the gate voltage, the transport is investigated in both the regime where sequential tunneling is dominating as well as the Coulomb blockaded regime, where cotunneling is the leading transport process. When sequential tunneling is dominating, the transport is mediated by both single electrons tunneling as well as processes that involve the creation and annihilation of Cooper pairs. In the Coulomb blockaded regime, transport is driven by cotunneling processes by transitions via virtual states. The results here show that four-terminal measurements can be a useful tool to characterize the properties of Majorana bound states with finite overlap and charging energy.
Secondly, we study the optical activity of tilted nodal loop semimetals. The inherent Hall conductivity of topological materials makes the Kerr effect an excellent tool for investigating their properties. Here we first calculate the full conductivity tensor for a tilted nodal loop semimetal, where the tilt is in the $ k_{x} - k_{y} $ plane. The conductivity tensor allows us to calculate the Kerr effect. We study this both for a thin film and a bulk material and we fin, in general, that the Kerr effect is large, similar to other topological materials.
Finally, we investigate electronic hydrodynamics in anomalous Hall insulators. First we derive the Navier-Stokes equations for topological materials and show that they are modified due to the Berry curvature. Secondly, we consider the flow in a narrow channel and the application of a small electric field. In this case, the Hall current can be neglected since it is much smaller than the longitudinal current. Flow in narrow channels conventionally leads to Poiseuille flow. However, as shown, the Berry curvature modifies the flow profile and shifts the maximum of the current profile towards one of the edges. Thirdly, we study the flow in an infinite geometry. In this case, it is shown that the Berry curvature induces whirlpools as well as causing an asymmetry in the profile of the electrical potential. Experimentally this can be observed by measuring the non-local resistance.Limit theorems for additive functionals of the fractional Brownian motion
http://hdl.handle.net/10993/48227
Title: Limit theorems for additive functionals of the fractional Brownian motion
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<br/>Author, co-author: Jaramillo, Arturo; Nourdin, Ivan; Nualart, David; Peccati, GiovanniINTERFACIAL COVALENT CHEMICAL BONDING: TOWARDS THERMOREVERSIBLE ADHESION
http://hdl.handle.net/10993/48214
Title: INTERFACIAL COVALENT CHEMICAL BONDING: TOWARDS THERMOREVERSIBLE ADHESION
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<br/>Author, co-author: Hassouna, Lilia
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<br/>Abstract: Many industrial sectors like automotive and aeronautic industries are moving toward the use of multi-material devices and composite materials. Reversible adhesion becomes then increasingly important as it allows to structurally join dissimilar materials and keep them together during the material’s useful life, while allowing the easy repair of damaged parts or recycling of raw materials. One way to achieve this property is by thermoreversible covalent bonding based on Diels-Alder and its retro Diels-Alder reaction. This “click” reaction occurs between a diene and a dienophile to form an adduct at a certain temperature, then this adduct can be dissociated on command by simple heating. The investigation of the adduct dissociation via retro Diels-Alder reaction is key in understanding the adhesion reversibility based on these systems. In this work an already formed Diels-Alder adduct is synthesized then grafted on plasma polymer coatings or self assembled monolayers. These two different types of surfaces offer different environments for the molecules. Afterwards, a protocol for reaction monitoring based on TOF-SIMS spectroscopy was developed which allowed the determination of kinetic and thermodynamic parameters of the interfacial reaction on both surfaces. The effect of the adducts environment on the reaction was then elucidated by comparing the obtained values. Investigation of the same reaction in solution using 1H NMR spectroscopy confirmed the observations made on the effect of molecules immobilisation on the reaction. Essentially, the more the molecules are immobilized the lower is the energy barrier and the higher is the entropy contribution. Finally, the feasibility of interfacial adhesion based on this system was explored.Quantum-mechanical force balance between multipolar dispersion and Pauli repulsion in atomic van der Waals dimers
http://hdl.handle.net/10993/48121
Title: Quantum-mechanical force balance between multipolar dispersion and Pauli repulsion in atomic van der Waals dimers
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<br/>Author, co-author: Vaccarelli, Ornella; Fedorov, Dmitry; Stoehr, Martin; Tkatchenko, AlexandreNonequilibrium thermodynamics of non-ideal chemical reaction networks
http://hdl.handle.net/10993/48120
Title: Nonequilibrium thermodynamics of non-ideal chemical reaction networks
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<br/>Author, co-author: Avanzini, Francesco; Penocchio, Emanuele; Falasco, Gianmaria; Esposito, Massimiliano
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<br/>Abstract: All current formulations of nonequilibrium thermodynamics of open chemical reaction networks rely on the assumption of non-interacting species. We develop a general theory that accounts for interactions between chemical species within a mean-field approach using activity coefficients. Thermodynamic consistency requires that rate equations do not obey standard mass-action kinetics but account for the interactions with concentration dependent kinetic constants. Many features of the ideal formulations are recovered. Crucially, the thermodynamic potential and the forces driving non-ideal chemical systems out of equilibrium are identified. Our theory is general and holds for any mean-field expression of the interactions leading to lower bounded free energies.Nonequilibrium thermodynamics of light-induced reactions
http://hdl.handle.net/10993/48119
Title: Nonequilibrium thermodynamics of light-induced reactions
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<br/>Author, co-author: Penocchio, Emanuele; Rao, Riccardo; Esposito, Massimiliano
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<br/>Abstract: Current formulations of nonequilibrium thermodynamics of open chemical reaction networks only consider chemostats as free-energy sources sustaining nonequilibrium behaviors. Here, we extend the theory to include incoherent light as a source of free energy. We do so by relying on a local equilibrium assumption to derive the chemical potential of photons relative to the system they interact with. This allows us to identify the thermodynamic potential and the thermodynamic forces driving light-reacting chemical systems out-of-equilibrium. We use this framework to treat two paradigmatic photochemical mechanisms describing light-induced unimolecular reactions—namely, the adiabatic and diabatic mechanisms—and highlight the different thermodynamics they lead to. Furthermore, using a thermodynamic coarse-graining procedure, we express our findings in terms of commonly measured experimental quantities, such as quantum yields.The discrepancy between min-max statistics of Gaussian and Gaussian-subordinated matrices
http://hdl.handle.net/10993/48107
Title: The discrepancy between min-max statistics of Gaussian and Gaussian-subordinated matrices
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<br/>Author, co-author: Peccati, Giovanni; Turchi, NicolaMagneto-optical activity in nonmagnetic hyperbolic nanoparticles
http://hdl.handle.net/10993/48091
Title: Magneto-optical activity in nonmagnetic hyperbolic nanoparticles
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<br/>Author, co-author: Kuttruff, Joel; Gabbani, Alessio; Petrucci, Gaia; Zhao, Yingqi; Iarossi, Marzia; Pedrueza Villalmanzo, Esteban; Dmitriev, Alexandre; Parracino, Antonietta; Strangi, Giuseppe; De Angelis, Francesco; Brida, Daniele; Pineider, Francesco; Maccaferri, Nicolò
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<br/>Abstract: Active nanophotonics can be realized by controlling the optical properties of materials with external magnetic fields. Here, we explore the influence of optical anisotropy on the magneto-optical activity in non-magnetic hyperbolic nanoparticles. We demonstrate that the magneto-optical response is driven by fundamental electric and magnetic dipole modes induced by the hyperbolic dispersion. Magnetic circular dichroism experiments confirm the theoretical predictions and reveal tunable magneto-optical activity across the visible and near infrared spectral range.Chemical vapor deposition of CoFe2O4 micropillar arrays with enhanced magnetic properties
http://hdl.handle.net/10993/48078
Title: Chemical vapor deposition of CoFe2O4 micropillar arrays with enhanced magnetic properties
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<br/>Author, co-author: Aspe, B.; Malyeyev, Artem; Vakilinejad, A.; Menguelti, K.; Michels, Andreas; Bahlawane, NaoufalEncoding Hidden Information onto Surfaces Using Polymerized Cholesteric Spherical Reflectors
http://hdl.handle.net/10993/48070
Title: Encoding Hidden Information onto Surfaces Using Polymerized Cholesteric Spherical Reflectors
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<br/>Author, co-author: Geng, Yong; Kizhakidathazhath, Rijeesh; Lagerwall, Jan
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<br/>Abstract: The omnidirectional Bragg reflection of cholesteric liquid crystals molded into spheres turns them into narrow-band retroreflectors with distinct circular polarization. It is shown that these cholesteric spherical reflectors (CSRs)
can encode information onto surfaces for far-field optical read-out without false positives, as the selective retroreflectivity allows the background to be easily subtracted. In order to hide the encoding from detection by the human eye, the retroreflection band is tuned to the near-UV or IR spectra, allowing ubiquitous deployment of CSRs in human-populated environments. This opens diverse application opportunities, for instance, in supporting safe robotic navigation and in augmented reality. A key breakthrough is our ability to permanently embed CSRs in a binder such that undesired scattering and reflections are minimized. This is achieved by realizing CSRs as shells that are polymerized from the liquid crystalline state. The resulting shrinkage around an incompressible fluid deforms the thinnest region of each shell such that it ruptures at a well-defined point. This leaves a single small hole in every CSR that gives access to the interior, allowing complete embedding in the binder with optimized refractive index, minimizing visibility.SNR-Based GNSS-R for Coastal Sea-Level Altimetry
http://hdl.handle.net/10993/48062
Title: SNR-Based GNSS-R for Coastal Sea-Level Altimetry
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<br/>Author, co-author: Tabibi, Sajad; Sauveur, Renaldo; Guerrier, Kelly; Metayer, Gerard; Francis, Olivier
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<br/>Abstract: Geodetic Global Navigation Satellite System reflectometry (GNSS-R) uses ground-based signals of opportunity to retrieve sea levels at an intermediate spatial scale. Geodetic GNSS-R is based on the simultaneous reception of Line-of-Sight (LoS) and its coherent GNSS sea surface reflection (non-LOS) signals. The scope of this paper is to present geodetic GNSS-R applied to sea level altimetry. Signal-to-Noise Ratio (SNR) measurements from a Commercial Off-The-Shelf (COTS) geodetic-quality GNSS station at the Haiti Coast Guard Base in Port-au-Prince is used to retrieve sea levels in the International Terrestrial Reference Frame 2014 (ITRF2014). The GNSS-R sea levels are compared with those of the OTT Radar Level Sensor (RLS) installed vertically below the GNSS antenna. The Root-Mean-Square Error (RMSE) between the geodetic GNSS-R sea levels and OTT RLS records is 3.43 cm, with a correlation of 0.96. In addition, the complex differences between the OTT RLS records and 15-min GNSS-R sea levels using Global Positioning System (GPS) and Globalnaya Navigazionnaya Sputnikovaya Sistema (or Global Navigation Satellite System; GLONASS) signals for all the eight major tidal constituents are in mm-level agreement. Therefore, geodetic GNSS-R can be used as a complementary approach to the conventional method for sea level studies in a stable terrestrial reference frame.QKD parameter estimation by two-universal hashing leads to faster convergence to the asymptotic rate
http://hdl.handle.net/10993/48038
Title: QKD parameter estimation by two-universal hashing leads to faster convergence to the asymptotic rate
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<br/>Author, co-author: Ostrev, Dimiter
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<br/>Abstract: This paper proposes and proves security of a QKD protocol which uses two-universal hashing instead of random sampling to estimate the number of bit flip and phase flip errors. For this protocol, the difference between asymptotic and finite key rate decreases with the number $n$ of qubits as $cn^{-1}$, where $c$ depends on the security parameter. For comparison, the same difference decreases no faster than $c'n^{-1/3}$ for an optimized protocol that uses random sampling and has the same asymptotic rate, where $c'$ depends on the security parameter and the error rate.Role of higher-order effects in spin-misalignment small-angle neutron scattering of high-pressure torsion nickel
http://hdl.handle.net/10993/48013
Title: Role of higher-order effects in spin-misalignment small-angle neutron scattering of high-pressure torsion nickel
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<br/>Author, co-author: Oba, Yojiro; Bersweiler, Mathias; Titov, Ivan; Adachi, Nozomu; Todaka, Yoshikazu; Gilbert, Elliot Paul; Steinke, Nina-Juliane; Metlov, Konstantin L.; Michels, Andreas