1,655 research outputs found
Dynamics of entanglement and transport in 1D systems with quenched randomness
Quenched randomness can have a dramatic effect on the dynamics of isolated 1D
quantum many-body systems, even for systems that thermalize. This is because
transport, entanglement, and operator spreading can be hindered by `Griffiths'
rare regions which locally resemble the many-body-localized phase and thus act
as weak links. We propose coarse-grained models for entanglement growth and for
the spreading of quantum operators in the presence of such weak links. We also
examine entanglement growth across a single weak link numerically. We show that
these weak links have a stronger effect on entanglement growth than previously
assumed: entanglement growth is sub-ballistic whenever such weak links have a
power-law probability distribution at low couplings, i.e. throughout the entire
thermal Griffiths phase. We argue that the probability distribution of the
entanglement entropy across a cut can be understood from a simple picture in
terms of a classical surface growth model. Surprisingly, the four length scales
associated with (i) production of entanglement, (ii) spreading of conserved
quantities, (iii) spreading of operators, and (iv) the width of the `front' of
a spreading operator, are characterized by dynamical exponents that in general
are all distinct. Our numerical analysis of entanglement growth between weakly
coupled systems may be of independent interest.Comment: 17 pages, 16 figure
Introduction to Translation.
We introduce here the inaugural issue of the new scientific journal Translation. The overarching aim of this endeavor is to establish a new forum for a broad spectrum of research in the area of protein synthesis in living systems ranging from structural biochemical, evolutionary and regulatory aspects of translation to the fundamental questions related to post-translational control of somatic phenomena in multicellular organisms including human behavior and health. The journal will publish high quality research articles, provide novel insights, ask provocative questions and discuss new hypothesis in this emerging field. Launching a new journal is always challenging. We hope that strong criteria for the peer-review process, transparency of the editorial policy and the scientific reputation of its founders, editors and editorial board assure the success of Translation; and we rely on continuing support of the scientific community in all aspects of the journal's activity
Deconfined quantum critical points: symmetries and dualities
The deconfined quantum critical point (QCP), separating the N\'eel and
valence bond solid phases in a 2D antiferromagnet, was proposed as an example
of D criticality fundamentally different from standard
Landau-Ginzburg-Wilson-Fisher {criticality}. In this work we present multiple
equivalent descriptions of deconfined QCPs, and use these to address the
possibility of enlarged emergent symmetries in the low energy limit. The
easy-plane deconfined QCP, besides its previously discussed self-duality, is
dual to fermionic quantum electrodynamics (QED), which has its own
self-duality and hence may have an O(4) symmetry. We propose
several dualities for the deconfined QCP with spin symmetry
which together make natural the emergence of a previously suggested
symmetry rotating the N\'eel and VBS orders. These emergent symmetries are
implemented anomalously. The associated infra-red theories can also be viewed
as surface descriptions of 3+1D topological paramagnets, giving further insight
into the dualities. We describe a number of numerical tests of these dualities.
We also discuss the possibility of "pseudocritical" behavior for deconfined
critical points, and the meaning of the dualities and emergent symmetries in
such a scenario.Comment: Published version, 44 pages + references, 4 figures. A summary of
main results in p7-
Emergent Symmetry at the N\'eel to Valence-Bond-Solid Transition
We show numerically that the `deconfined' quantum critical point between the
N\'eel antiferromagnet and the columnar valence-bond-solid, for a square
lattice of spin-1/2s, has an emergent symmetry. This symmetry allows
the N\'eel vector and the valence-bond-solid order parameter to be rotated into
each other. It is a remarkable 2+1-dimensional analogue of the symmetry that appears in the scaling limit for the
spin-1/2 Heisenberg chain. The emergent is strong evidence that the
phase transition in the 2+1D system is truly continuous, despite the violations
of finite-size scaling observed previously in this problem. It also implies
surprising relations between correlation functions at the transition. The
symmetry enhancement is expected to apply generally to the critical
two-component Abelian Higgs model (non-compact model). The result
indicates that in three dimensions there is an -symmetric conformal
field theory which has no relevant singlet operators, so is radically different
to conventional Wilson-Fisher-type conformal field theories.Comment: 4+epsilon pages, 6 figure
Length Distributions in Loop Soups
Statistical lattice ensembles of loops in three or more dimensions typically
have phases in which the longest loops fill a finite fraction of the system. In
such phases it is natural to ask about the distribution of loop lengths. We
show how to calculate moments of these distributions using or
and O(n) models together with replica techniques. The
resulting joint length distribution for macroscopic loops is Poisson-Dirichlet
with a parameter fixed by the loop fugacity and by symmetries of the
ensemble. We also discuss features of the length distribution for shorter
loops, and use numerical simulations to test and illustrate our conclusions.Comment: 4.5 page
Deconfined Quantum Criticality, Scaling Violations, and Classical Loop Models
Numerical studies of the N\'eel to valence-bond solid phase transition in 2D
quantum antiferromagnets give strong evidence for the remarkable scenario of
deconfined criticality, but display strong violations of finite-size scaling
that are not yet understood. We show how to realise the universal physics of
the Neel-VBS transition in a 3D classical loop model (this includes the
interference effect that suppresses N\'eel hedgehogs). We use this model to
simulate unprecedentedly large systems (of size ). Our results are
compatible with a direct continuous transition at which both order parameters
are critical, and we do not see conventional signs of first-order behaviour.
However, we find that the scaling violations are stronger than previously
realised and are incompatible with conventional finite-size scaling over the
size range studied, even if allowance is made for a weakly/marginally
irrelevant scaling variable. In particular, different determinations of the
anomalous dimensions and yield very
different results. The assumption of conventional finite-size scaling gives
estimates which drift to negative values at large , in violation of
unitarity bounds. In contrast, the behaviour of correlators on scales much
smaller than is consistent with large positive anomalous dimensions.
Barring an unexpected reversal in behaviour at still larger sizes, this implies
that the transition, if continuous, must show unconventional finite-size
scaling, e.g. from a dangerously irrelevant scaling variable. Another
possibility is an anomalously weak first-order transition. By analysing the
renormalisation group flows for the non-compact model (-component
Abelian Higgs model) between two and four dimensions, we give the simplest
scenario by which an anomalously weak first-order transition can arise without
fine-tuning of the Hamiltonian.Comment: 20 pages, 19 figure
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