arXiv subjects

You-gang Feng

Publications and source records attributed to You-gang Feng.

10 recordsLinked to original sources

arXiv2012

Self-similar transformations of lattice-Ising models at critical temperatures

We classify geometric blocks that serve as spin carriers into simple blocks and compound blocks by their topologic connectivity, define their fractal dimensions and describe the relevant transformations. By the hierarchical property of transformations and a block-spin scaling law we obtain a relation between the block spin and its carrier's fractal dimension. By mapping we set up a block-spin Gaussian model and get a formula connecting the critical point and the minimal fractal dimension of the carrier, which guarantees the uniqueness of a fixed point corresponding to the critical point, changing the complicated calculation of critical point into the simple one of the minimal fractal dimension. The numerical results of critical points with high accuracy for five conventional lattice-Ising models prove our method very effective and may be suitable to all lattice-Ising models. The origin of fluctuations in structure at critical temperature is discussed. Our method not only explains the problems met in the renormalization-group theory, but also provides a useful tool for deep investigation of the critical behaviour.

physics.gen-ph↗

arXiv2012

Ising model: secondary phase transition

Lttice-spin phonons are considered, which make the heat capacity at the critical temperature satisfy experimental observations better. There is a BEC phase transition in an Ising model attributable to the lattice-spin phonons. We proved that the spin-wave theory only is available after BEC transition, and the magnons have the same characteristics as the lattice-spin phonons', resulting from quantum effect. Energy-level overlap effect at ultralow temperature is found. A prediction of BEC phase transition in a crystal is put forward as our theory generalization.

physics.gen-ph↗

arXiv2011

Ising model: Elementary excitation and nonsingular heat capacity at critical temperature

We find a new parameter vector q to describe spin correlations and fluctuation characteristics. The conservation of scalar q indicates there are simple harmonic motions of q, and the motion quantum is called block-spin phonon like the phonon in a crystal, resulting in nonsingular heat capacity at T . The harmonic motions show there are hierarchies and symmetries of fluctuations, and the soft modes lead to the interactions of block-spin phonons of different frequencies.

physics.gen-ph↗

arXiv2010

Critical points with high accuracy and fluctuation origin of 2 and 3-dimensional Ising models

We proposed a new universal method for significantly increasing accuracy of critical points of 2 and 3-dimensional Ising models and exploring fluctuation mechanism. The method is based on analysis of block fractals and the renormalization group theory. We discussed hierarchies and rescaling rule of the self similar transformations, and define a fractal dimension of an ordered block, which minimum corresponds to a fixed point of the transformations. By the connectivity we divide the blocks into two types: irreducible and reducible. We find there are two block spin states: single state and k-fold state, each of which relates to a system or a subsystem described by a block spin Gaussian model set up by mathematic map. Using the model we obtain a universal formula of critical points by the minimal fractal dimensions. We computed the critical points with high accuracy for three Ising models. It is the first time to find a critical point only requires a fractal edge, which causes fluctuations, and the point acts as a fluctuation attractor. Finally, we discussed a possibility of different block spins at the critical point.

physics.gen-ph↗

arXiv2010

Topological Structures of Cluster Spins for Ising Models

We discussed hierarchies and rescaling rule of the self similar transformations in Ising models, and define a fractal dimension of an ordered cluster, which minimum corresponds to a fixed point of the transformations. By the fractal structures we divide the clusters into two types: irreducible and reducible. A relationship of cluster spin with its coordination number and fractal dimension is obtained.

physics.gen-ph↗

arXiv2010

The Boundary Conditions Geometry in Lattice-Ising Model

We found that the differential topology of the lattice-system of Ising model determines whether there can be the continuous phase transition, the geometric topology of the space the lattice-system is embedded in determines whether the system can become ordered. If the system becomes ordered it may not admit the continuous phase transition. The spin-projection orientations are strongly influenced by the geometric topology of the space the lattice-system is embedded in.

physics.gen-ph↗

arXiv2007

Duality of momentum-energy and space-time on an almost complex manifold

We proved that under quantum mechanics a momentum-energy and a space-time are dual vector spaces on an almost complex manifold in position representation, and the minimal uncertainty relations are equivalent to the inner-product relations of their bases. In a microscopic sense, there exist locally a momentum-energy conservation and a space-time conservation. The minimal uncertainty relations refer to a local equilibrium state for a stable system, and the relations will be invariable in the special relativity. A supposition about something having dark property is proposed, which relates to a breakdown of time symmetry.

physics.gen-ph↗

arXiv2005

Spin-projection orientations in the plane square-lattice Ising model with periodic boundary conditions

The periodic boundary conditions changed the plane square-lattice Ising model to the torus-lattice system which restricts the spin-projection orientations. Only two of the three important spin-projection orientations, parallel to the x-axis or to the y-axis, are suited to the torus-lattice system. The infinitesimal difference of the free-energies of the systems between the two systems mentioned above makes their critical temperatures infinitely close to each other, but their topological fundamental groups are distinct.

quant-ph↗

arXiv2005

Microscopic origin of the second law of thermodynamics

We proved when random-variable fluctuations obey the central limit theorem the equality of the uncertainty relation corresponds to the thermodynamic equilibrium state. The inequality corresponds to the thermodynamic non-equilibrium state. The uncertainty relation is a quantum-mechanics expression of the second law of thermodynamics originated in wave-particle duality. Formulas of mean square-deviations changes adjusted by random fluctuations under the minimal uncertainty relation are obtained. Finally, an assumption is made which is waiting for examination. We except phase transitions in our discussion.

quant-ph↗

arXiv2005

Uncertainty relation and quantitative condition of inversion symmetry of time in many-particle system

We proved that the uncertainty relation fits in with many-particle system and the equality of the relation corresponds to the thermodynamic equilibrium state, the inequality of the relation corresponds to the thermodynamic non-equilibrium state for any quantum system. The microscopic origin of the second law of thermodynamics is certainly resulted in the wave-particle duality of matter. A quantitative condition of inversion symmetry of time is obtained.

quant-ph↗