61 research outputs found
Continuous Hamiltonian dynamics on digital quantum computers without discretization error
We introduce an algorithm to compute Hamiltonian dynamics on digital quantum
computers that requires only a finite circuit depth to reach an arbitrary
precision, i.e. achieves zero discretization error with finite depth. This
finite number of gates comes at the cost of an attenuation of the measured
expectation value by a known amplitude, requiring more shots per circuit. The
gate count for simulation up to time is with the
-norm of the Hamiltonian, without dependence on the precision desired on the
result, providing a significant improvement over previous algorithms. The only
dependence in the norm makes it particularly adapted to non-sparse
Hamiltonians. The algorithm generalizes to time-dependent Hamiltonians,
appearing for example in adiabatic state preparation. These properties make it
particularly suitable for present-day relatively noisy hardware that supports
only circuits with moderate depth.Comment: 5 page
Out-of-equilibrium dynamics of the XY spin chain from form factor expansion
We consider the XY spin chain with arbitrary time-dependent magnetic field
and anisotropy. We argue that a certain subclass of Gaussian states, called
Coherent Ensemble (CE) following [1], provides a natural and unified framework
for out-of-equilibrium physics in this model. We show that correlation
functions in the CE can be computed using form factor expansion and expressed
in terms of Fredholm determinants. In particular, we present exact
out-of-equilibrium expressions in the thermodynamic limit for the previously
unknown order parameter one-point function, dynamical two-point function and
equal-time three-point function.Comment: 44 page
Reconstructing particles in jets using set transformer and hypergraph prediction networks
The task of reconstructing particles from low-level detector response data to
predict the set of final state particles in collision events represents a
set-to-set prediction task requiring the use of multiple features and their
correlations in the input data. We deploy three separate set-to-set neural
network architectures to reconstruct particles in events containing a single
jet in a fully-simulated calorimeter. Performance is evaluated in terms of
particle reconstruction quality, properties regression, and jet-level metrics.
The results demonstrate that such a high dimensional end-to-end approach
succeeds in surpassing basic parametric approaches in disentangling individual
neutral particles inside of jets and optimizing the use of complementary
detector information. In particular, the performance comparison favors a novel
architecture based on learning hypergraph structure, HGPflow, which benefits
from a physically-interpretable approach to particle reconstruction.Comment: 17 pages, 21 figure
Fanny Copeland and the geographical imagination
Raised in Scotland, married and divorced in the English south, an adopted Slovene, Fanny Copeland (1872 – 1970) occupied the intersection of a number of complex spatial and temporal conjunctures. A Slavophile, she played a part in the formation of what subsequently became the Kingdom of Yugoslavia that emerged from the First World War. Living in Ljubljana, she facilitated the first ‘foreign visit’ (in 1932) of the newly formed Le Play Society (a precursor of the Institute of British Geographers) and guided its studies of Solčava (a then ‘remote’ Alpine valley system) which, led by Dudley Stamp and commended by Halford Mackinder, were subsequently hailed as a model for regional studies elsewhere. Arrested by the Gestapo and interned in Italy during the Second World War, she eventually returned to a socialist Yugoslavia, a celebrated figure. An accomplished musician, linguist, and mountaineer, she became an authority on (and populist for) the Julian Alps and was instrumental in the establishment of the Triglav National Park. Copeland’s role as participant observer (and protagonist) enriches our understanding of the particularities of her time and place and illuminates some inter-war relationships within G/geography, inside and outside the academy, suggesting their relative autonomy in the production of geographical knowledge
Exploring new physics frontiers through numerical relativity
The demand to obtain answers to highly complex problems within strong-field gravity has been met with significant progress in the numerical solution of Einstein's equations - along with some spectacular results - in various setups. We review techniques for solving Einstein's equations in generic spacetimes, focusing on fully nonlinear evolutions but also on how to benchmark those results with perturbative approaches. The results address problems in high-energy physics, holography, mathematical physics, fundamental physics, astrophysics and cosmology
Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study
Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe
Z’ boson & contact interaction searches at the LHC
An overview of recently published searches for Z' boson and contact interaction signatures in dilepton and dijet final states with the ATLAS and CMS detectors at the LHC
Latest search for dilepton resonances and constraints on Dark Matter mediators
The LHC offers the best prospects for direct production of WIMP Dark Matter (DM) and gauge bosons arising from a dark sector beyond the Standard Model (SM). In particular, a neutral Z’_{DM} boson mediating DM-SM interactions is a prime target for resonance searches, and its couplings can thereby be constrained within the broad context of mediator-based simplified DM models. In this poster I introduce the Z’_{DM} phenomenology in the dilepton final state and present the latest bounds on the relevant simplified models imposed by searches for high mass dilepton resonances with the ATLAS detector
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