100,021 research outputs found
Dimension of non-trivial online forms
Non-trivial on-line forms (N-TOFs) are a type of
form that we believe is becoming widely prevalent
with the preference for on-line services in many
areas of everyday life. We define N-TOFs as forms
that are critical to the life and wellbeing of the form
filler (aka user). By virtue of this, they are frequently
complex in terms of structure, mechanics and
content required. Forms providing access to
government, financial, employment and educational
services are commonly N-TOFs, depending upon
the specifics of the service to which they relate.
Other examples of N-TOFs include: tax forms,
benefits forms, immigration forms, social housing
applications, etc. The non-trivial nature of such
forms principally arises from their close relationship
to the quality of life of their users.
A pernicious feature of service provision through NTOFs
is that form design could in fact reflect a
design bias that limits access to a service. Put
simply, an N-TOF could by its character impair
legitimate access to a service. For example there
are forms that could be judged as unnecessarily
complex for the user. Hence the interest in N-TOFs
relates closely to the agendas of: design for all; and
professional ethics. On a related matter it is evident
that in N-TOFs some of their onerous elements
serve as a means of user authentication. For
example, having to enter comprehensive personal
details is used to help confirm a user's identity.
Hence an onerous or repetitive aspect of a form
can be accounted for as a legitimate design choic
Strange correlations in spin-1 Heisenberg antiferromagnets
We study the behavior of the recently proposed "strange correlator" [Phys.
Rev. Lett. {\bf 112}, 247202 (2014)] in spin-1 Heisenberg antiferromagnetic
chains with uniaxial single-ion anisotropy. Using projective quantum Monte
Carlo, we are able to directly access the strange correlator in a variety of
phases, as well as to examine its critical behavior at the quantum phase
transition between trivial and non-trivial symmetry protected topological
phases. After finding the expected long-range behavior in these two symmetry
conserving phases, we go on to verify the topological nature of two-leg and
three-leg spin-1 Heisenberg antiferromagnetic ladders. This demonstrates the
power of the strange correlator in distinguishing between trivial and
non-trivial symmetry protected topological phases.Comment: 7 pages, 6 figure
A Holographic Theory for the Phase Transitions Between Fermionic Symmetry-protected Topological States
In an earlier work we developed a holographic theory for the phase transition
between bosonic symmetry-protected topological (SPT) states. This paper is a
continuation of it. Here we present the holographic theory for fermionic SPT
phase transitions. We show that in any dimension , the critical states of
fermionic SPT phase transitions has an emergent symmetry and can be
realized on the boundary of a -dimensional bulk SPT with an extra
symmetry.Comment: 35 pages, 10 figure
Quantum phase transition as an interplay of Kitaev and Ising interactions
We study the interplay between the Kitaev and Ising interactions on both
ladder and two dimensional lattices. We show that the ground state of the
Kitaev ladder is a symmetry-protected topological (SPT) phase, which is
protected by a symmetry. It is confirmed by
the degeneracy of the entanglement spectrum and non-trivial phase factors
(inequivalent projective representations of the symmetries), which are obtained
within infinite matrix-product representation of numerical density matrix
renormalization group. We derive the effective theory to describe the
topological phase transition on both ladder and two-dimensional lattices, which
is given by the transverse field Ising model with/without next-nearest neighbor
coupling. The ladder has three phases, namely, the Kitaev SPT, symmetry broken
ferro/antiferromagnetic order and classical spin-liquid. The non-zero quantum
critical point and its corresponding central charge are provided by the
effective theory, which are in full agreement with the numerical results, i.e.,
the divergence of entanglement entropy at the critical point, change of the
entanglement spectrum degeneracy and a drop in the ground-state fidelity. The
central charge of the critical points are either c=1 or c=2, with the
magnetization and correlation exponents being 1/4 and 1/2, respectively. In the
absence of frustration, the 2D lattice shows a topological phase transition
from the spin-liquid state to the long-range ordered Ising phase
at finite ratio of couplings, while in the presence of frustration, an
order-by-disorder transition is induced by the Kitaev term. The 2D classical
spin-liquid phase is unstable against the addition of Kitaev term toward an
ordered phase before the transition to the spin-liquid state.Comment: 16 pages, 18 figure
Quantum Multicriticality in Disordered Weyl Semimetal
In electronic band structure of solid state material, two band touching
points with linear dispersion appear in pair in the momentum space. When they
annihilate with each other, the system undergoes a quantum phase transition
from three-dimensional Weyl semimetal (WSM) phase to a band insulator phase
such as Chern band insulator (CI) phase. The phase transition is described by a
new critical theory with a `magnetic dipole' like object in the momentum space.
In this paper, we reveal that the critical theory hosts a novel disorder-driven
quantum multicritical point, which is encompassed by three quantum phases,
renormalized WSM phase, CI phase, and diffusive metal (DM) phase. Based on the
renormalization group argument, we first clarify scaling properties around the
band touching points at the quantum multicritical point as well as all phase
boundaries among these three phases. Based on numerical calculations of
localization length, density of states and critical conductance distribution,
we next prove that a localization-delocalization transition between the CI
phase with a finite zero-energy density of states (zDOS) and DM phase belongs
to an ordinary 3D unitary class. Meanwhile, a localization-delocalization
transition between the Chern insulator phase with zero zDOS and a renormalized
Weyl semimetal (WSM) phase turns out to be a direct phase transition whose
critical exponent . We interpret these numerical results by a
renormalization group analysis on the critical theory.Comment: 23 pages with 14 figures and 4 table
- …