29,203 research outputs found
Pseudo entropy and pseudo-Hermiticity in quantum field theories
In this paper, we explore the concept of pseudo R\'enyi entropy within the
context of quantum field theories (QFTs). The transition matrix is constructed
by applying operators situated in different regions to the vacuum state.
Specifically, when the operators are positioned in the left and right Rindler
wedges respectively, we discover that the logarithmic term of the pseudo
R\'enyi entropy is necessarily real. In other cases, the result might be
complex. We provide direct evaluations of specific examples within
2-dimensional conformal field theories (CFTs). Furthermore, we establish a
connection between these findings and the pseudo-Hermitian condition. Our
analysis reveals that the reality or complexity of the logarithmic term of
pseudo R\'enyi entropy can be explained through this pseudo-Hermitian
framework.
Additionally, we investigate the divergent term of the pseudo R\'enyi
entropy. Interestingly, we observe a universal divergent term in the second
pseudo R\'enyi entropy within 2-dimensional CFTs. This universal term is solely
dependent on the conformal dimension of the operator under consideration. For
-th pseudo R\'enyi entropy (), the divergent term is intricately
related to the specific details of the underlying theory.Comment: 26+12 pages, many figure
A comparative study of two molecular mechanics models based on harmonic potentials
We show that the two molecular mechanics models, the stick-spiral and the
beam models, predict considerably different mechanical properties of materials
based on energy equivalence. The difference between the two models is
independent of the materials since all parameters of the beam model are
obtained from the harmonic potentials. We demonstrate this difference for
finite width graphene nanoribbons and a single polyethylene chain comparing
results of the molecular dynamics (MD) simulations with harmonic potentials and
the finite element method with the beam model. We also find that the difference
strongly depends on the loading modes, chirality and width of the graphene
nanoribbons, and it increases with decreasing width of the nanoribbons under
pure bending condition. The maximum difference of the predicted mechanical
properties using the two models can exceed 300% in different loading modes.
Comparing the two models with the MD results of AIREBO potential, we find that
the stick-spiral model overestimates and the beam model underestimates the
mechanical properties in narrow armchair graphene nanoribbons under pure
bending condition.Comment: 40 pages, 21 figure
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