5,017 research outputs found
The quasi-particle gap in a disordered boson Hubbard model in two dimensions
We investigate the behavior of the quasi-particle energy gap near quantum
phase transitions in a two-dimensional disordered boson Hubbard model at a
commensurate filling. Via Monte Carlo simulations of ensembles with fixed
numbers of particles, we observe the behavior of the gap as a function of the
tuning parameter for various strength of diagonal disorder. For weak disorder,
we find that gapped Mott insulating phase is sustained up to the transition
point and disappears only in a superfluid, strongly supporting a direct
Mott-insulator-to-superfluid transition. Bose glass behavior, insulating with
vanishing gap, appears only when the strength of disorder is bigger than a
critical value
Increasing and decreasing entanglement characteristics for continuous variables by a local photon subtraction
We investigate how the entanglement characteristics of a non-Gaussian
entangled state are increased or decreased by a local photon subtraction
operation. The non-Gaussian entangled state is generated by injecting a
single-mode non-Gaussian state and a vacuum state into a 50:50 beam splitter.
We consider a photon-added coherent state and an odd coherent state as a
single-mode non-Gaussian state. In the regime of small amplitude, we show that
the performance of quantum teleportation and the second-order
Einstein-Podolsky- Rosen-type correlation can both be enhanced, whereas the
degree of entanglement decreases, for the output state when a local photon
subtraction operation is applied to the non-Gaussian entangled state. The
counterintuitive effect is more prominent in the limit of nearly zero
amplitude.Comment: Published version, 7 pages, 3 figure
Quantum Monte Carlo Study of Disordered Fermions
We study a strongly correlated fermionic model with attractive interactions
in the presence of disorder in two spatial dimensions. Our model has been
designed so that it can be solved using the recently discovered meron-cluster
approach. Although the model is unconventional it has the same symmetries of
the Hubbard model. Since the naive algorithm is inefficient, we develop a new
algorithm by combining the meron-cluster technique with the directed-loop
update. This combination allows us to compute the pair susceptibility and the
winding number susceptibility accurately. We find that the s-wave
superconductivity, present in the clean model, does not disappear until the
disorder reaches a temperature dependent critical strength. The critical
behavior as a function of disorder close to the phase transition belongs to the
Berezinsky-Kosterlitz-Thouless universality class as expected. The fermionic
degrees of freedom, although present, do not appear to play an important role
near the phase transition.Comment: published version, more data added to Fig 5 and clarifications in
text, 8 page
Chronic rhinosinusitis with nasal polyps in older adults : clinical presentation, pathophysiology, and comorbidity
Purpose of Review Chronic rhinosinusitis and nasal polyps (CRSwNP) is a common condition that significantly affects patients' life. This work aims to provide an up-to-date overview of CRSwNP in older adults, focusing on its aging-related clinical presentations, pathophysiology, and comorbidity associations including asthma. Recent Findings Recent large population-based studies using nasal endoscopy have shown that CRSwNP is a mostly late-onset disease. Age-related changes in physiologic functions, including nasal epithelial barrier dysfunction, may underlie the incidence and different clinical presentations of CRSwNP in older adults. However, there is still a paucity of evidence on the effect of aging on phenotypes and endotypes of CRSwNP. Meanwhile, late-onset asthma is a major comorbid condition in patients with CRSwNP; they frequently present with type 2 inflammatory signatures that are refractory to conventional treatments when they are comorbid. However, as they are more commonly non-atopic, causative factors other than classical atopic sensitization, such as Staphylococcus aureus specific IgE sensitization, are suggested to drive the type 2 inflammation. There are additional comorbidity associations in older patients with CRSwNP, including those with chronic otitis media and head and neck malignancy. Age is a major determinant for the incidence and clinical presentations of CRSwNP. Given the heterogeneity in phenotypes and endotypes, longitudinal investigations are warranted to elucidate the effects of aging on CRSwNP
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