Physical Review A
Study on Fermion Exchange in Quantum Theory of Ring Polymers
The Russell B. Thompson research group of the University of Waterloo in Canada and Philip A. LeMaitre of the University of Innsbruck in Austria have studied the fermion exchange in the quantum theory of ring polymers. Relevant research results were published in Physical Review A recently.
Using polymer self consistent field theory, researchers have established the mapping relationship between fermion exchange and repulsive volume in quantum classical isomorphism. In addition to exchange, researchers also found that quantum particles can be accurately represented as ring polymers in classical statistical mechanics, and their profiles are parameterized by inverse thermal energy, often referred to as virtual time.
The research team provided strong evidence for the fermion exchange approximation in the self consistent field theory of cyclic polymers, especially based on the symmetry of cyclic polymers, and demonstrated that it is reasonable to use full contour interaction instead of equal virtual time interaction in the mean field image. In addition, the study also reveals that the thermal path of removing the prohibition is essentially equivalent to antisymmetric exchange.
The researchers calculated the electron density of beryllium atom by using the self consistent field theory of ring polymer without considering the classical correlation, and the results are in good agreement with the Hartree Fock theory ignoring the Coulomb correlation. It is concluded that the total energy is consistent within 6%. Although it is far from the chemical accuracy, considering that the field theory equation is derived from the first principle of zero free parameter, this result is still worthy of attention.
In addition, the researchers also discussed the potential method to improve the theoretical consistency by more accurately representing the electron electron self interaction in the self consistent field theory, and deeply discussed the quantum basic significance of the quantum classical mapping between the fermion exchange and the thermal trajectory repulsion volume.
Relevant paper information:
https://doi.org/10.1103/PhysRevA.109.052819
Nature
Scientists propose a wave function matching method for solving quantum multibody problems
Dean Lee's research team at Michigan State University in the United States proposed a wave function matching method for solving quantum many body problems. Relevant research results were recently published in Nature.
It is reported that ab initio computing plays a crucial role in people's basic understanding of quantum many body systems. These systems span many sub domains, from strongly correlated fermions to quantum chemistry, from atomic and molecular systems to nuclear physics. One of the major challenges is building accurate computing systems. The complex interactions in the system make it particularly difficult to choose an appropriate calculation method.
The research team solved this problem by introducing a method called wave function matching. Wave function matching transforms the interaction between particles, making the wave function match the interaction that is easy to calculate in a limited range. This method breaks through the limitations of the computing system, solves problems such as the cancellation of Monte Carlo symbols, and enables the calculation that could not be carried out to run.
Researchers have successfully applied this method to lattice Monte Carlo simulation of light nuclei, medium mass nuclei, neutron matter and nuclear matter. They use high fidelity chiral effective field theory to interact, and the results are highly consistent with empirical data. These results not only provide new insights into nuclear interactions, but also are expected to solve the long-term problem of accurately reproducing nuclear binding energy, charge radius and nuclear matter saturation in ab initio calculations.
Relevant paper information:
https://doi.org/10.1038/s41586-024-07422-z
Nature Genetics
Heterogeneity and evolutionary mechanism of meningiomas revealed
The David R. Raleigh research group of the University of California, San Francisco, USA has revealed the spatial genome, biochemical and cellular mechanisms of meningioma heterogeneity and evolution. The research was recently published online in Nature Genetics.
Using spatial methods, researchers identified the genomic, biochemical and cellular mechanisms that link intratumoral heterogeneity with the molecular, temporal and spatial evolution of high-level meningiomas. Research shows that different gene and protein expression programs in tumors distinguish high-level meningiomas, and the current classification system classifies these tumors into one group. Analysis of paired primary and recurrent meningiomas showed that the spatial expansion of subclone copy number variation was related to drug resistance.
Using cell types sequenced by single cell RNA, the researchers performed multiple sequence immunofluorescence and spin off display on the meningioma space transcriptome, and found that the reduction of immune invasion, the reduction of MAPK signal transmission, the increase of PI3K-AKT signal transmission, and the increase of cell proliferation were related to the recurrence of meningioma. In order to translate these findings into preclinical models, the researchers used CRISPR interference and pedigree tracking methods to determine a combination therapy for intratumoral heterogeneity in meningioma cell co culture.
Relevant paper information:
https://doi.org/10.1038/s41588-024-01747-1
Journal of the National Academy of Sciences
Scientists discover topological polaron in halide perovskite
The Feliciano Giustino team of the University of Texas at Austin in the United States discovered the topological polaron in halide perovskite. Relevant research results were recently published in the Journal of the National Academy of Sciences.
Through the first principle simulation on the length scale, the research team found that halide perovskite has rich and unique polarons, including small polarons, large polarons and charge density waves, and explained various experimental observations.
Researchers found that these emerging quasiparticles support topological nontrivial phonon fields with quantized topological charges, making them a nonmagnetic analogy of spiral Bloch points in magnetic Skimi sublattices.
It is reported that halide perovskite is a revolutionary high-quality semiconductor, which can be used for solar energy collection and energy-saving lighting. More and more evidence shows that the special photoelectric properties of these materials may be derived from unconventional electron phonon coupling, and the formation of polarons and self trapping excitons may be the key to understanding these properties.
Relevant paper information:
https://doi.org/10.1073/pnas.2318151121
