3,867 research outputs found
Estimating the efficiency turn-on curve for a constant-threshold trigger without a calibration dataset
Many particle physics experiments use constant threshold triggers, where the
trigger threshold is in an online estimator that can be calculated quickly by
the trigger module. Offline data analysis then calculates a more precise
offline estimator for the same quantity, for example the event energy. The
efficiency curve is a step function in the online estimator, but not in the
offline estimator.
One typically obtains the shape of the efficiency curve in the offline
estimator by way of a calibration dataset, where the true rate of events at
each value of the offline estimator is measured once and compared to the rate
observed in the physics dataset. For triggers with a fixed threshold condition,
it is sometimes possible to bootstrap the trigger efficiency curve without use
of a calibration dataset. This is useful to verify stability of a calibration
over time when calibration data cannot be taken often enough. It also makes it
possible to use datasets for which no calibration is available. This paper
describes the method and the conditions that must be met for it to be
applicable
Exotic Ising dynamics in a Bose-Hubbard model
We explore the dynamical properties of a one-dimensional Bose-Hubbard model,
where two bosonic species interact via Feshbach resonance. We focus on the
region in the phase diagram which is described by an effective, low-energy
ferromagnetic Ising model in both transverse and longitudinal fields. In this
regime, we numerically calculate the dynamical structure factor of the
Bose-Hubbard model using the time-evolving block decimation method. In the
ferromagnetic phase, we observe both the continuum of excitations and the bound
states in the presence of a longitudinal field. Near the Ising critical point,
we observe the celebrated E8 mass spectrum in the excited states. We also point
out possible measurements which could be used to detect these excitations in an
optical lattice experiment.Comment: 5 pages, 3 figures, as publishe
Phase transitions and adiabatic preparation of a fractional Chern insulator in a boson cold atom model
We investigate the fate of hardcore bosons in a Harper-Hofstadter model which
was experimentally realized by Aidelsburger et al. [Nature Physics 11 , 162
(2015)] at half filling of the lowest band. We discuss the stability of an
emergent fractional Chern insulator (FCI) state in a finite region of the phase
diagram that is separated from a superfluid state by a first-order transition
when tuning the band topology following the protocol used in the experiment.
Since crossing a first-order transition is unfavorable for adiabatically
preparing the FCI state, we extend the model to stabilize a featureless
insulating state. The transition between this phase and the topological state
proves to be continuous, providing a path in parameter space along which an FCI
state could be adiabatically prepared. To further corroborate this statement,
we perform time-dependent DMRG calculations which demonstrate that the FCI
state may indeed be reached by adiabatically tuning a simple product state.Comment: 7 pages, 7 figures, published versio
Phase diagram of the isotropic spin-3/2 model on the z=3 Bethe lattice
We study an SU(2) symmetric spin-3/2 model on the z=3 Bethe lattice using the
infinite Time Evolving Block Decimation (iTEBD) method. This model is shown to
exhibit a rich phase diagram. We compute the expectation values of several
order parameters which allow us to identify a ferromagnetic, a ferrimagnetic, a
anti-ferromagnetic as well as a dimerized phase. We calculate the entanglement
spectra from which we conclude the existence of a symmetry protected
topological phase that is characterized by S=1/2 edge spins. Details of the
iTEBD algorithm used for the simulations are included
Absence of orthogonality catastrophe after a spatially inhomogeneous interaction quench in Luttinger liquids
We investigate the Loschmidt echo, the overlap of the initial and final
wavefunctions of Luttinger liquids after a spatially inhomogeneous interaction
quench. In studying the Luttinger model, we obtain an analytic solution of the
bosonic Bogoliubov-de Gennes equations after quenching the interactions within
a finite spatial region. As opposed to the power law temporal decay following a
potential quench, the interaction quench in the Luttinger model leads to a
finite, hardly time dependent overlap, therefore no orthogonality catastrophe
occurs. The steady state value of the Loschmidt echo after a sudden
inhomogeneous quench is the square of the respective adiabatic overlaps. Our
results are checked and validated numerically on the XXZ Heisenberg chain.Comment: 5 pages, 4 figures, published versio
Database support of detector operation and data analysis in the DEAP-3600 Dark Matter experiment
The DEAP-3600 detector searches for dark matter interactions on a 3.3 tonne
liquid argon target. Over nearly a decade, from start of detector construction
through the end of the data analysis phase, well over 200 scientists will have
contributed to the project. The DEAP-3600 detector will amass in excess of 900
TB of data representing more than 10 particle interactions, a few of
which could be from dark matter. At the same time, metadata exceeding 80 GB
will be generated. This metadata is crucial for organizing and interpreting the
dark matter search data and contains both structured and unstructured
information.
The scale of the data collected, the important role of metadata in
interpreting it, the number of people involved, and the long lifetime of the
project necessitate an industrialized approach to metadata management.
We describe how the CouchDB and the PostgreSQL database systems were
integrated into the DEAP detector operation and analysis workflows. This
integration provides unified, distributed access to both structured
(PostgreSQL) and unstructured (CouchDB) metadata at runtime of the data
analysis software. It also supports operational and reporting requirements
Isometric Tensor Network States in Two Dimensions
Tensor network states (TNS) are a promising but numerically challenging tool
for simulating two-dimensional (2D) quantum many-body problems. We introduce an
isometric restriction of the TNS ansatz that allows for highly efficient
contraction of the network. We consider two concrete applications using this
ansatz. First, we show that a matrix-product state representation of a 2D
quantum state can be iteratively transformed into an isometric 2D TNS. Second,
we introduce a 2D version of the time-evolving block decimation algorithm
(TEBD) for approximating the ground state of a Hamiltonian as an isometric
TNS, which we demonstrate for the 2D transverse field Ising model.Comment: 5 pages, 4 figure
Full counting statistics in the Haldane-Shastry chain
We present analytical and numerical results regarding the magnetization full
counting statistics (FCS) of a subsystem in the ground-state of the
Haldane-Shastry chain. Exact Pfaffian expressions are derived for the cumulant
generating function, as well as any observable diagonal in the spin basis. In
the limit of large systems, the scaling of the FCS is found to be in agreement
with the Luttinger liquid theory. The same techniques are also applied to
inhomogeneous deformations of the chain. This introduces a certain amount of
disorder in the system; however we show numerically that this is not sufficient
to flow to the random singlet phase, that corresponds to chains with
uncorrelated bond disorder.Comment: 15 pages, 7 figure
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