Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 31 for “"Spin Glasses"”.
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Statistical and Algorithmic Thresholds in Spin Glasses
This thesis studies spin glasses, disordered complex systems originating in statistical physics. Such systems model optimization, sampling, and inference problems from probability and statistics, which are of fundamental importance to modern data science. In particular, spin glasses provide natural …
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Mechanical relaxations, spin glasses and 1/f resistance noise
… resistance changes in mesoscopic samples of the spin glass CuMn. A large sensitivity of the resistance to the relative configuration of spins in the sample was found with a magnitude and temperature dependence in accordance with predictions of universal conductance fluctuations. Predictions of …
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Mechanical relaxations, spin glasses and 1/f resistance noise
… the resistance to the relative configuration of spins in the sample was found with a magnitude and temperature dependence in accordance with predictions of universal conductance fluctuations. Predictions of the droplet theory of spin glasses were tested and no evidence was found for chaotic …
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Disordered systems and quantum algorithms: from spin glasses to neural networks
… can solve disordered systems, with a focus on spin glasses and neural networks. We first introduce several examples of disordered systems and have an overview of spin glasses. Then we introduce a cyclic quantum annealing protocol on D-Wave’s 5000-qubit processor that explores deeper energy …
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Non-equilibrium physics: from spin glasses to machine and neural learning
… dynamics island and study the ability of driven spin-glasses to perform discriminative tasks such as novelty detection and classification. Finally, we conclude our exploration at the long-term memory and natural dynamics kingdom and investigate the generative modeling ability in many-body …
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Correlation lengths and times in CuMn spin glasses from simulation and experiment
… study correlation lengths and times of Cul-xMnx spin glasses. Several results are found: a single model inspired by the Parisi solution explains both the experimentally observed aging and equilibrium fluctuation phenomena in Cul-xMnx, and as one expects the fluctuation dynamics in and out of …
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Correlation Lengths and Times in Copper Manganese Spin Glasses From Simulation and Experiment
… study correlation lengths and times of Cu1-xMn x spin glasses. Several results are found: a single model inspired by the Parisi solution explains both the experimentally observed aging and equilibrium fluctuation phenomena in Cu1-xMnx, and as one expects the fluctuation dynamics in and out of …
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Synthesis and Characterization of Heusler Compounds with Non-Collinear Magnetic Structure - From Spin Glasses to Spin Reorientation
… free permanent magnets, magnetocalorics, spin transfer torque devices and tunnel junctions. Apart from that, magnetic Heusler systems are also interesting for fundamental research since some members host skyrmion lattices and other magnetically complex orders. The search for new Heusler …
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Investigation and Optimization of Extraordinary Electroconductance (EEC) Sensors & The Role of Magnetic Disorder in the Formation of Spin Glasses
… Role of Magnetic Disorder in the Formation of Spin Glasses</underline></p><p>This thesis presents data on the magnetic properties of two classes of layered spin S=1/2 antiferromagnetic quasi-triangular lattice materials: Cu<sub>2(1-x)</sub>Zn<sub>2x</sub>(OH)<sub>3</sub>NO<sub>3</sub> …
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Phase Transitions in Disordered Systems: I. Exciton/electron-Hole Liquid/plasma System in Germanium and Ii. Amorphous Ferromagnets and Spin Glasses
In Part I of this thesis, we present experimental evidence demonstrating that a metal-insulator (M-I) phase transition can occur separately from the liquid-gas (L-G) transition in the exciton/electron-hole (e-h) gas/e-h liquid system in stressed Ge. Using a strain well to confine the photoexcited …
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Phase transitions in disordered systems: I. exciton/electron-hole liquid/plasma system in germanium and II. amorphous ferromagnets and spin glasses
… thermodynamic properties of a system of Ising spins interacting with various random {X)tentials in the Bethe-Peierls-Wiss (BPW) approximation. When the effective number of neighbors z approaches infinity, we show that all the magnetic properties arising from the BPW approximation, the …
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Computational Hardness in Random Optimization Problems from the Overlap Gap Property
… on the problems of random k-SAT and mean-field spin glasses. Our results are: • It is known that random k-SAT has a satisfying assignment with high probability up to clause density [formula], while the best known algorithm (Fix) finds a satisfying assignment up to clause density [formula]. We …
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Stirred spin glass models of in vivo protein folding
"The similarity between spin glasses and proteins is that both have complex energy landscapes with multiple energy minima and barriers. The approach to equilibrium in such systems has been previously studied. We present here a ""stirred"" spin glass whose equilibrium is constantly being perturbed …
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Experimental study of the spin-glass phase diagram
The spin-glass phase diagram is examined as a function of temperature, magnetic field, random anisotropy, and uniaxial anisotropy and the results are compared to recent mean-field theories. It is clearly demonstrated through measurements of the magnetic relaxation processes in the amorphous …
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Spin Systems far from Equilibrium: Aging and Dynamic Phase Transition
… as possible, we study in both cases simple spin systems. Using Monte Carlo simulations we first investigate aging in three-dimensional Ising spin glasses as well as in two-dimensional Ising models with disorder quenched to low temperatures. The time-dependent dynamical correlation length …
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Computational studies of thermal and quantum phase transitions approached through non-equilibrium quenching
… methods, I study more complex systems such as spin-glasses and random graphs. The techniques allow us to investigate the problems efficiently. From the classical perspective, using the NEQ approach I verify the universality class of the 3D Ising spin-glasses. I also investigate the random …
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Electrical noise study of spin glass dynamics in mesocopic CuMn
The electrical resistance of the archetypal spin glass CuMn is surprisingly sensitive to small changes in the spin configuration. This enhanced sensitivity results from long-range electron quantum interference at low temperatures. Due to this effect, substantial resistance noise is produced by …
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Electrical noise study of spin glass dynamics in mesoscopic copper manganese
The electrical resistance of the archetypal spin glass $\underline{\rm Cu}$Mn is surprisingly sensitive to small changes in the spin configuration. This enhanced sensitivity results from long-range electron quantum interference at low temperatures. Due to this effect, substantial resistance noise …
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Zero field NMR study on a spin glass: Iron-doped 2H-niobium diselenide
We have used spin echoes to study the 93Nb NQR in 2H-NbSe2Fex. We measured (intensity)x(temperature), and T1P (spin-lattice relaxation parameter) and T2 (spin-spin relaxation time) as a function of temperature. Our data reveal dramatic difference between non-spin glass samples (x=O, 0.25%, 1% and …
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Zero Field Nmr Study on a Spin Glass: Iron-Doped 2hydrogen-Niobium Diselenide
We have used spin echoes to study the ('93)Nb NQR in 2H-NbSe(,2)Fe(,x). We measured (intensity) x (temperature), and T(,1P) (spin-lattice relaxation parameter) and T(,2) (spin-spin relaxation time) as a function of temperature. Our data reveal dramatic difference between non-spin glass samples (x = …
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