315 research outputs found
Phases of two-dimensional spinless lattice fermions with first-quantized deep neural-network quantum states
First-quantized deep neural network techniques are developed for analyzing
strongly coupled fermionic systems on the lattice. Using a Slater-Jastrow
inspired ansatz which exploits deep residual networks with convolutional
residual blocks, we approximately determine the ground state of spinless
fermions on a square lattice with nearest-neighbor interactions. The
flexibility of the neural-network ansatz results in a high level of accuracy
when compared to exact diagonalization results on small systems, both for
energy and correlation functions. On large systems, we obtain accurate
estimates of the boundaries between metallic and charge ordered phases as a
function of the interaction strength and the particle density
The Gongfu Approach to Teaching and Doing Chinese Philosophy across Cultures
This paper introduces a method of doing and teaching East Asian philosophy transculturally. The method underlies a pedagogy that has proven successful with students from diverse international backgrounds studying primarily in English, which suggests its potential for the wider scholarly community. The method centres on the practice, or gongfu, of doing philosophy with classical Chinese texts. The gongfu approach emphasizes the skill of interpreting and analysing texts within the context of the traditional works themselves. We have found that this skills-based approach to analysis bears much philosophical fruit. It does so, moreover, without subordinating the texts, their ideas, and their arguments to other more academically predominant frameworks. Or in more positive terms, it allows and encourages students to critically philosophize with the early Confucian and Daoist texts on their own terms, and to then creatively bring those unique insights and perspectives to bear on contemporary life.
This paper first introduces the gongfu approach to doing and teaching Chinese philosophy and its distinctive characteristics. It then contextualizes the value of this method through critically examining the nature of Chinese philosophy and how we can do Chinese philosophy in English. (How Chinese is it, and in what ways?) Throughout I offer short case studies from our program. I conclude by highlighting its promise as a mode (or valuable component) of transcultural philosophizing and briefly reflect on some reservations one might have
Smooth Muscle Cell Phenotypic Switch Induced by Traditional Cigarette Smoke Condensate: A Holistic Overview
Cigarette smoke (CS) is a risk factor for inflammatory diseases, such as atherosclerosis. CS condensate (CSC) contains lipophilic components that may represent a systemic cardiac risk factor. To better understand CSC effects, we incubated mouse and human aortic smooth muscle cells (SMCs) with CSC. We evaluated specific markers for contractile [i.e., actin, aortic smooth muscle (ACTA2), calponin-1 (CNN1), the Kruppel-like factor 4 (KLF4), and myocardin (MYOCD) genes] and inflammatory [i.e., IL-1 beta, and IL-6, IL-8, and galectin-3 (LGALS-3) genes] phenotypes. CSC increased the expression of inflammatory markers and reduced the contractile ones in both cell types, with KLF4 modulating the SMC phenotypic switch. Next, we performed a mass spectrometry-based differential proteomic approach on human SMCs and could show 11 proteins were significantly affected by exposition to CSC (FC >= 2.7, p <= 0.05). These proteins are active in signaling pathways related to expression of pro-inflammatory cytokines and IFN, inflammasome assembly and activation, cy-toskeleton regulation and SMC contraction, mitochondrial integrity and cellular response to oxidative stress, proteostasis control via ubiquitination, and cell proliferation and epithelial-to-mesenchymal transition. Through specific bioinformatics resources, we showed their tight functional correlation in a close interaction niche mainly orchestrated by the interferon-induced double-stranded RNA-activated protein kinase (alternative name: protein kinase RNA-activated; PKR) (EIF2AK2/PKR). Finally, by combining gene expression and protein abundance data we obtained a hybrid network showing reciprocal integration of the CSC-deregulated factors and indicating KLF4 and PKR as the most relevant factors
Can translation invariant systems exhibit a Many-Body Localized phase?
This note is based on a talk by one of us, F. H., at the conference PSPDE II,
Minho 2013. We review some of our recent works related to (the possibility of)
Many-Body Localization in the absence of quenched disorder (in particular
arXiv:1305.5127,arXiv:1308.6263,arXiv:1405.3279). In these works, we provide
arguments why systems without quenched disorder can exhibit `asymptotic'
localization, but not genuine localization.Comment: To appear in the Proceedings of the conference Particle systems and
PDE's - II, held at the Center of Mathematics of the University of Minho in
December 201
Lines and continuum sky emission in the near infrared: observational constraints from deep high spectral resolution spectra with GIANO-TNG
Aims Determining the intensity of lines and continuum airglow emission in the
H-band is important for the design of faint-object infrared spectrographs.
Existing spectra at low/medium resolution cannot disentangle the true
sky-continuum from instrumental effects (e.g. diffuse light in the wings of
strong lines). We aim to obtain, for the first time, a high resolution infrared
spectrum deep enough to set significant constraints on the continuum emission
between the lines in the H-band. Methods During the second commissioning run of
the GIANO high-resolution infrared spectrograph at La Palma Observatory, we
pointed the instrument directly to the sky and obtained a deep spectrum that
extends from 0.97 to 2.4 micron. Results The spectrum shows about 1500 emission
lines, a factor of two more than in previous works. Of these, 80% are
identified as OH transitions; half of these are from highly excited molecules
(hot-OH component) that are not included in the OH airglow emission models
normally used for astronomical applications. The other lines are attributable
to O2 or unidentified. Several of the faint lines are in spectral regions that
were previously believed to be free of line emission. The continuum in the
H-band is marginally detected at a level of about 300
photons/m^2/s/arcsec^2/micron, equivalent to 20.1 AB-mag/arcsec^2. The observed
spectrum and the list of observed sky-lines are published in electronic format.
Conclusions Our measurements indicate that the sky continuum in the H-band
could be even darker than previously believed. However, the myriad of airglow
emission lines severely limits the spectral ranges where very low background
can be effectively achieved with low/medium resolution spectrographs. We
identify a few spectral bands that could still remain quite dark at the
resolving power foreseen for VLT-MOONS (R ~6,600).Comment: 7 pages, 4 figures, to be published in Astronomy & Astrophysic
On the origin of the non-detection of metastable HeI in the upper atmosphere of the hot Jupiter WASP-80b
We aim to narrow down the origin of the non-detection of the metastable HeI
triplet at about 10830 A obtained for the hot Jupiter WASP-80b. We measure the
X-ray flux of WASP-80 from archival observations and use it as input to scaling
relations accounting for the coronal [Fe/O] abundance ratio to infer the
extreme-ultraviolet (EUV) flux in the 200-504 A range, which controls the
formation of metastable HeI. We run three dimensional (magneto) hydrodynamic
simulations of the expanding planetary upper atmosphere interacting with the
stellar wind to study the impact on the HeI absorption of the stellar
high-energy emission, the He/H abundance ratio, the stellar wind, and the
possible presence of a planetary magnetic field up to 1 G. For a low stellar
EUV emission, which is favoured by the measured logR'HK value, the HeI
non-detection can be explained by a solar He/H abundance ratio in combination
with a strong stellar wind, or by a sub-solar He/H abundance ratio, or by a
combination of the two. For a high stellar EUV emission, the non-detection
implies a sub-solar He/H abundance ratio. A planetary magnetic field is
unlikely to be the cause of the non-detection. The low EUV stellar flux, driven
by the low [Fe/O] coronal abundance, is the likely primary cause of the HeI
non-detection. High-quality EUV spectra of nearby stars are urgently needed to
improve the accuracy of high-energy emission estimates, which would then enable
one to employ the observations to constrain the planetary He/H abundance ratio
and the stellar wind strength. This would greatly enhance the information that
can be extracted from HeI atmospheric characterisation observations.Comment: Accepted for publication on A&A, 20 page
The GAPS Programme with HARPS-N at TNG XV. A substellar companion around a K giant star identified with quasi-simultaneous HARPS-N and GIANO measurements
Context. Identification of planetary companions of giant stars is made
difficult because of the astrophysical noise, that may produce radial velocity
(RV) variations similar to those induced by a companion. On the other hand any
stellar signal is wavelength dependent, while signals due to a companion are
achromatic. Aims. Our goal is to determine the origin of the Doppler periodic
variations observed in the thick disk K giant star TYC 4282-605-1 by HARPS-N at
the Telescopio Nazionale Galileo (TNG) and verify if they can be due to the
presence of a substellar companion. Methods. Several methods have been used to
exclude the stellar origin of the observed signal including detailed analysis
of activity indicators and bisector and the analysis of the photometric light
curve. Finally we have conducted an observational campaign to monitor the near
infrared (NIR) RV with GIANO at the TNG in order to verify whether the NIR
amplitude variations are comparable with those observed in the visible.
Results. Both optical and NIR RVs show consistent variations with a period at
101 days and similar amplitude, pointing to the presence of a companion
orbiting the target. The main orbital properties obtained for our giant star
with a derived mass of M=0.97+-0.03M_sun are
M_Psini=10.78+-0.12MJ;P=101.54+-0.05days;e=0.28+-0.01 and a=0.422+-0.009AU. The
chemical analysis shows a significant enrichment in the abundance of Nai, Mgi,
Ali and S i while the rest of analyzed elements are consistent with the solar
value demonstrating that the chemical composition corresponds with an old K
giant (age = 10.1 Gyr) belonging to local thick disk. Conclusions. We conclude
that the substellar companion hypothesis for this K giant is the best
explanation for the observed periodic RV variation. This study also shows the
high potential of multi-wavelength RV observations for the validation of planet
candidates.Comment: Accepted in Journal reference A&A 14/06/201
NetKet 3: Machine Learning Toolbox for Many-Body Quantum Systems
We introduce version 3 of NetKet, the machine learning toolbox for many-body quantum physics. NetKet is built around neural-network quantum states and provides efficient algorithms for their evaluation and optimization. This new version is built on top of JAX, a differentiable programming and accelerated linear algebra framework for the Python programming language. The most significant new feature is the possibility to define arbitrary neural network ansätze in pure Python code using the concise notation of machine-learning frameworks, which allows for just-in-time compilation as well as the implicit generation of gradients thanks to automatic differentiation. NetKet 3 also comes with support for GPU and TPU accelerators, advanced support for discrete symmetry groups, chunking to scale up to thousands of degrees of freedom, drivers for quantum dynamics applications, and improved modularity, allowing users to use only parts of the toolbox as a foundation for their own code
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