10 research outputs found
The pinning quantum phase transition in a Tonks Girardeau gas: diagnostics by ground state fidelity and the Loschmidt echo
We study the pinning quantum phase transition in a Tonks-Girardeau gas, both
in equilibrium and out-of-equilibrium, using the ground state fidelity and the
Loschmidt echo as diagnostic tools. The ground state fidelity (GSF) will have a
dramatic decrease when the atomic density approaches the commensurate density
of one particle per lattice well. This decrease is a signature of the pinning
transition from the Tonks to the Mott insulating phase. We study the
applicability of the fidelity for diagnosing the pinning transition in
experimentally realistic scenarios. Our results are in excellent agreement with
recent experimental work. In addition, we explore the out of equilibrium
dynamics of the gas following a sudden quench with a lattice potential. We find
all properties of the ground state fidelity are reflected in the Loschmidt echo
dynamics i.e., in the non equilibrium dynamics of the Tonks-Girardeau gas
initiated by a sudden quench of the lattice potential
Loschmidt echo in one-dimensional interacting Bose gases
We explore Loschmidt echo in two regimes of one-dimensional (1D) interacting
Bose gases: the strongly interacting Tonks-Girardeau (TG) regime, and the
weakly-interacting mean-field regime. We find that the Loschmidt echo of a TG
gas decays as a Gaussian when small perturbations are added to the Hamiltonian
(the exponent is proportional to the number of particles and the magnitude of a
small perturbation squared). In the mean-field regime the Loschmidt echo decays
faster for larger interparticle interactions (nonlinearity), and it shows
richer behavior than the TG Loschmidt echo dynamics, with oscillations
superimposed on the overall decay.Comment: Comparison between Tonks-Girardeau and mean-field fidelities
corrected; see new Figure 4 and the "Note added". New references are include
High resolution spectroscopic study of 10Be-Λ
Spectroscopy of a 10Be-Λ hypernucleus was carried out at JLab Hall C using the (e, e′K+) reaction. A new magnetic spectrometer system (SPL+HES+HKS), specifically designed for high resolution hypernuclear spectroscopy, was used to obtain an energy spectrum with a resolution of ∼0.78 MeV (FWHM). The well-calibrated spectrometer system of the present experiment using p(e, e′K+)Λ, Σ0 reactions allowed us to determine the energy levels ; and the binding energy of the ground-state peak (mixture of 1− and 2− states) was found to be B- Λ=8.55±0.07(stat.)±0.11(sys.) MeV. The result indicates that the ground-state energy is shallower than that of an emulsion study by about 0.5 MeV which provides valuable experimental information on the charge symmetry breaking effect in the ΛN interaction
Spectroscopy of the neutron-rich hypernucleus HeΛ7 from electron scattering
The missing mass spectroscopy of the HeΛ7 hypernucleus was performed using the Li7(e, e ′K+)HeΛ7 reaction at the Thomas Jefferson National Accelerator Facility Hall C. The Λ- binding energy of the ground-state (1/2+) was determined with a smaller error than that of the previous measurement, being BΛ=5.55±0.10stat.±0.11sys.MeV. The experiment also provided new insight into charge symmetry breaking in p-shell hypernuclear systems. Finally, a peak at BΛ=3.65±0.20stat. ±0.11sys.MeV was observed and assigned as a mixture of 3/2+ and 5/2+ states, confirming the "gluelike" behavior of Λ, which makes an unstable state in He6 stable against neutron emission
Annotation and initial evaluation of a large annotated German oncological corpus
Objective: We present the Berlin-Tübingen-Oncology corpus (BRONCO), a large and freely available corpus of shuffled sentences from German oncological discharge summaries annotated with diagnosis, treatments, medications, and further attributes including negation and speculation. The aim of BRONCO is to foster reproducible and openly available research on Information Extraction from German medical texts. Materials and methods: BRONCO consists of 200 manually deidentified discharge summaries of cancer patients. Annotation followed a structured and quality-controlled process involving 2 groups of medical experts to ensure consistency, comprehensiveness, and high quality of annotations. We present results of several state-of-the-art techniques for different IE tasks as baselines for subsequent research. Results: The annotated corpus consists of 11 434 sentences and 89 942 tokens, annotated with 11 124 annotations for medical entities and 3118 annotations of related attributes. We publish 75% of the corpus as a set of shuffled sentences, and keep 25% as held-out data set for unbiased evaluation of future IE tools. On this held-out dataset, our baselines reach depending on the specific entity types F1-scores of 0.72-0.90 for named entity recognition, 0.10-0.68 for entity normalization, 0.55 for negation detection, and 0.33 for speculation detection. Discussion: Medical corpus annotation is a complex and time-consuming task. This makes sharing of such resources even more important. Conclusion: To our knowledge, BRONCO is the first sizable and freely available German medical corpus. Our baseline results show that more research efforts are necessary to lift the quality of information extraction in German medical texts to the level already possible for English
First Direct Measurement of the Proton’s Weak Charge
Abstract The Qweak experiment, which took data at Jefferson Lab in the period 2010 - 2012, will precisely determine the weak charge of the proton by measuring the parity-violating asymmetry in elastic e-p scattering at 1.1 GeV using a longitudinally polarized electron beam and a liquid hydrogen target at a low momentum transfer of Q2 = 0.025 (GeV/c)2. The weak charge of the proton is predicted by the Standard Model and any significant deviation would indicate physics beyond the Standard Model. The technical challenges and experimental apparatus for measuring the weak charge of the proton will be discussed, as well as the method of extracting the weak charge of the proton. The results from a small subset of the data, that has been published, will also be presented. Furthermore an update will be given of the current status of the data analysis