16,446 research outputs found
Momentum polarization: an entanglement measure of topological spin and chiral central charge
Topologically ordered states are quantum states of matter with topological
ground state degeneracy and quasi-particles carrying fractional quantum numbers
and fractional statistics. The topological spin is an
important property of a topological quasi-particle, which is the Berry phase
obtained in the adiabatic self-rotation of the quasi-particle by . For
chiral topological states with robust chiral edge states, another fundamental
topological property is the edge state chiral central charge . In this paper
we propose a new approach to compute the topological spin and chiral central
charge in lattice models by defining a new quantity named as the momentum
polarization. Momentum polarization is defined on the cylinder geometry as a
universal subleading term in the average value of a "partial translation
operator". We show that the momentum polarization is a quantum entanglement
property which can be computed from the reduced density matrix, and our
analytic derivation based on edge conformal field theory shows that the
momentum polarization measures the combination of
topological spin and central charge. Numerical results are obtained for two
example systems, the non-Abelian phase of the honeycomb lattice Kitaev model,
and the Laughlin state of a fractional Chern insulator described by a
variational Monte Carlo wavefunction. The numerical results verifies the
analytic formula with high accuracy, and further suggests that this result
remains robust even when the edge states cannot be described by a conformal
field theory. Our result provides a new efficient approach to characterize and
identify topological states of matter from finite size numerics.Comment: 13 pages, 8 figure
Higher-order properties and Bell-inequality violation for the three-mode enhanced squeezed state
By extending the usual two-mode squeezing operator to the three-mode squeezing operator , we
obtain the corresponding three-mode squeezed coherent state. The state's
higher-order properties, such as higher-order squeezing and higher-order
sub-Possonian photon statistics, are investigated. It is found that the new
squeezed state not only can be squeezed to all even orders but also exhibits
squeezing enhancement comparing with the usual cases. In addition, we examine
the violation of Bell-inequality for the three-mode squeezed states by using
the formalism of Wigner representation
Probing ultralight dark fields in cosmological and astrophysical systems
Dark matter constitutes of the total energy in our universe, but its
nature remains elusive. Among the assortment of viable dark matter candidates,
particles and fields with masses lighter than , called
ultralight dark matter, stand out as particularly promising thanks to their
feasible production mechanisms, consistency with current observations, and
diverse and testable predictions. In light of ongoing and forthcoming
experimental and observational efforts, it is important to advance the
understanding of ultralight dark matter from theoretical and phenomenological
perspectives: How does it interact with itself, ordinary matter, and gravity?
What are some promising ways to detect it?
In this thesis, we aim to explore the dynamics and interaction of ultralight
dark matter and other astrophysically accessible hypothetical fields in a
relatively model-independent way. Without making specific assumptions about
their ultraviolet physics, we first demonstrate a systematic approach for
constructing a classical effective field theory for both scalar and vector dark
fields and discuss conditions for its validity. Then, we explore the
interaction of ultralight dark fields, both gravitational and otherwise, within
various contexts such as nontopological solitons, neutron stars, and
gravitational waves.Comment: PhD thesi
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