3 resultados para Critical Fluctuations

em Boston University Digital Common


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Using Monte Carlo simulations we study a coarse­grained model of a water layer confined in a fixed disordered matrix of hydrophobic nanoparticles at different particle concentrations c. For c = 0 we find a 1st order liquid­liquid phase transition (LLPT) ending in one critical point at low pressure P. For c > 0 our simulations are consistent with a LLPT line ending in two critical points at low and high pressure. For c = 25% at high P and low temperature T we find a dramatic decrease of compressibility, thermal expansion coefficient, and specific heat. Surprisingly, the effect is present also for c as low as 2.4%. We conclude that even a small presence of nanoscopic hydrophobes can drastically suppress thermodynamic fluctuations, making the detection of the LLPT more difficult.

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Campus-based publishing partnerships offer the academy greater control over the intellectual products that it helps create. To fully realize this potential, such partnerships will need to evolve from informal working alliances to long-term, programmatic collaborations. SPARCâ s Campus-based Publishing Partnerships: A Guide to Critical Issues addresses issues relevant to building sound and balanced partnerships, including: Establishing governance and administrative structures; Identifying funding models that accommodate the objectives of both libraries and presses; Defining a partnershipâ s objectives to align the missions of the library and the press; Determining what services to provide; and Demonstrating the value of the collaboration. SPARCâ s Campus-based Publishing Partnerships will help libraries, presses, and academic units to define effective partnerships capable of supporting innovative approaches to campus-based publishing.

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We investigate numerically the ground state phase diagram of the one-dimensional extended Hubbard model, including an on--site interaction U and a nearest--neighbor interaction V. We focus on the ground state phases of the model in the V >> U region, where previous studies have suggested the possibility of dominant superconducting pairing fluctuations before the system phase separates at a critical value V=V_PS. Using quantum Monte Carlo methods on lattices much larger than in previous Lanczos diagonalization studies, we determine the boundary of phase separation, the Luttinger Liquid correlation exponent K_rho, and other correlation functions in this region. We find that phase separation occurs for V significantly smaller than previously reported. In addition, for negative U, we find that a uniform state re-enters from phase separation as the electron density is increased towards half filling. For V < V_PS, our results show that superconducting fluctuations are not dominant. The system behaves asymptotically as a Luttinger Liquid with K_rho < 1, but we also find strong low-energy (but gapped) charge-density fluctuations at a momentum not expected for a standard Luttinger Liquid.