Browsing ElektrikElektronik Mühendisliği / Electrical  Electronics Engineering by KHAS Author "Berker, A. Nihat"
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Across dimensions: Two and threedimensional phase transitions from the iterative renormalizationgroup theory of chains
Sharp two and threedimensional phase transitional magnetization curves are obtained by an iterative renormalizationgroup coupling of Ising chains, which are solved exactly. The chains by themselves do not have a phase transition or nonzero magnetization, but the method reflects crossover from temperaturelike to fieldlike renormalizationgroup flows as the mechanism for the higherdimensional phase transitions. The magnetization of each chain acts, via the interaction constant, as a magnetic ...

Complete density calculations of qstate Potts and clock models: Reentrance of interface densities under symmetry breaking
All local bondstate densities are calculated for qstate Potts and clock models in three spatial dimensions, d = 3. The calculations are done by an exact renormalization group on a hierarchical lattice, including the density recursion relations, and simultaneously are the MigdalKadanoff approximation for the cubic lattice. Reentrant behavior is found in the interface densities under symmetry breaking, in the sense that upon lowering the temperature, the value of the density first increases and ...

Devil's staircase continuum in the chiral clock spin glass with competing ferromagneticantiferromagnetic and leftright chiral interactions
The chiral clock spinglass model with q = 5 states with both competing ferromagneticantiferromagnetic and leftright chiral frustrations is studied in d = 3 spatial dimensions by renormalizationgroup theory. The global phase diagram is calculated in temperature antiferromagnetic bond concentration p random chirality strength and rightchirality concentration c. The system has a ferromagnetic phase a multitude of different chiral phases a chiral spinglass phase and a critical (algebraically) ...

Frustrated Potts model: Multiplicity eliminates chaos via reentrance
The frustrated qstate Potts model is solved exactly on a hierarchical lattice, yielding chaos under rescaling, namely, the signature of a spinglass phase, as previously seen for the Ising (q = 2) model. However, the groundstate entropy introduced by the (q > 2)state antiferromagnetic Potts bond induces an escape from chaos as multiplicity q increases. The frustration versus multiplicity phase diagram has a reentrant (as a function of frustration) chaotic phase.

Lower lowercritical spinglass dimension from quenched mixedspatialdimensional spin glasses
By quenchedrandomly mixing local units of different spatial dimensionalities we have studied Ising spinglass systems on hierarchical lattices continuously in dimensionalities 1 <= d <= 3. The global phase diagram in temperature antiferromagnetic bond concentration and spatial dimensionality is calculated. We find that as dimension is lowered the spinglass phase disappears to zero temperature at the lowercritical dimension d(c) = 2.431. Our system being a physically realizable system this sets ...

Maximally random discretespin systems with symmetric and asymmetric interactions and maximally degenerate ordering
Discretespin systems with maximally random nearestneighbor interactions that can be symmetric or asymmetric ferromagnetic or antiferromagnetic including offdiagonal disorder are studied for the number of states q = 34 in d dimensions. We use renormalizationgroup theory that is exact for hierarchical lattices and approximate (MigdalKadanoff) for hypercubic lattices. For all d > 1 and all nonmfimte temperatures the system eventually renormalizes to a random single state thus signaling q x q ...

Metastable reversephase droplets within ordered phases: Renormalizationgroup calculation of field and temperature dependence of limiting size
Metastable reversephase droplets are calculated by renormalizationgroup theory by evaluating the magnetization of a droplet under magnetic field, matching the boundary condition with the reverse phase and noting whether the reversephase magnetization sustains. The maximal metastable droplet size and the discontinuity across the droplet boundary are thus calculated as a function of temperature and magnetic field for the Ising model in three dimensions. The method also yields hysteresis loops for ...

Phase transitions between different spinglass phases and between different chaoses in quenched random chiral systems
The leftright chiral and ferromagneticantiferromagnetic doublespinglass clock model with the crucially even number of states q = 4 and in three dimensions d = 3 has been studied by renormalizationgroup theory. We find for the first time to our knowledge four spinglass phases including conventional chiral and quadrupolar spinglass phases and phase transitions between spinglass phases. The chaoses in the different spinglass phases and in the phase transitions of the spinglass phases with ...