| 21. |
- Ade, P. A. R., et al.
(författare)
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XXIV. Cosmology from Sunyaev-Zeldovich cluster counts
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 594
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Tidskriftsartikel (refereegranskat)abstract
- We present cluster counts and corresponding cosmological constraints from the Planck full mission data set. Our catalogue consists of 439 clusters detected via their Sunyaev-Zeldovich (SZ) signal down to a signal-to-noise ratio of 6, and is more than a factor of 2 larger than the 2013 Planck cluster cosmology sample. The counts are consistent with those from 2013 and yield compatible constraints under the same modelling assumptions. Taking advantage of the larger catalogue, we extend our analysis to the two-dimensional distribution in redshift and signal-to-noise. We use mass estimates from two recent studies of gravitational lensing of background galaxies by Planck clusters to provide priors on the hydrostatic bias parameter, (1 - b). In addition, we use lensing of cosmic microwave background (CMB) temperature fluctuations by Planck clusters as an independent constraint on this parameter. These various calibrations imply constraints on the present-day amplitude of matter fluctuations in varying degrees of tension with those from the Planck analysis of primary fluctuations in the CMB; for the lowest estimated values of (1 b) the tension is mild, only a little over one standard deviation, while it remains substantial (3.7 sigma) for the largest estimated value. We also examine constraints on extensions to the base flat Lambda CDM model by combining the cluster and CMB constraints. The combination appears to favour non-minimal neutrino masses, but this possibility does little to relieve the overall tension because it simultaneously lowers the implied value of the Hubble parameter, thereby exacerbating the discrepancy with most current astrophysical estimates. Improving the precision of cluster mass calibrations from the current 10%-level to 1% would significantly strengthen these combined analyses and provide a stringent test of the base Lambda CDM model.
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| 22. |
- Dremov, Viacheslav V., et al.
(författare)
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Local Josephson vortex generation and manipulation with a Magnetic Force Microscope
- 2019
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Josephson vortices play an essential role in superconducting quantum electronics devices. Often seen as purely conceptual topological objects, 2π-phase singularities, their observation and manipulation are challenging. Here we show that in Superconductor—Normal metal—Superconductor lateral junctions Josephson vortices have a peculiar magnetic fingerprint that we reveal in Magnetic Force Microscopy (MFM) experiments. Based on this discovery, we demonstrate the possibility of the Josephson vortex generation and manipulation by the magnetic tip of a MFM, thus paving a way for the remote inspection and control of individual nano-components of superconducting quantum circuits.
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| 23. |
- Usachov, Dmitry Yu, et al.
(författare)
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Probing surface and bulk ground states of lanthanides: 4f moment orientation through 4d x-ray absorption spectroscopy
- 2024
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 110:7
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of the ground state of lanthanides (Ln) in Ln-based materials is fundamental for understanding their properties, particularly those related to magnetism. In crystalline materials, the magnitude and orientation of 4f magnetic moments are often strongly influenced by the crystal electric field (CEF), making them challenging to predict ab initio. This complexity is intensified in low-dimensional systems and nanostructures, where the CEF may vary significantly near surfaces and at interfaces. The related variations of the 4f ground state should be probed by methods with adjustable surface sensitivity. Here, we apply x-ray absorption spectroscopy (XAS) at the Ln 4d edge, along with modeling of XAS spectra, to probe the 4f ground state of Ln atoms both at the surface and in the bulk of LnRh2Si2 layered crystals. Our results explicitly reveal significant changes of the 4f ground state, which may lead to the reorientation of 4f moments at the surface compared to the bulk, driven by alterations of the CEF. We also provide a comprehensive database of calculated Ln 4d XAS spectra in numeric format for all lanthanides. Our findings will facilitate studies of Ln-based materials and molecular complexes by enabling comprehensive analysis of XAS data, including those obtained through magnetic linear and circular dichroism techniques, as well as related spectromicroscopy studies.
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| 24. |
- Golod, Taras, et al.
(författare)
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Reconfigurable Josephson Phase Shifter
- 2021
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 21:12, s. 5240-5246
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Tidskriftsartikel (refereegranskat)abstract
- Phase shifter is one of the key elements of quantum electronics. In order to facilitate operation and avoid decoherence, it has to be reconfigurable, persistent, and nondissipative. In this work, we demonstrate prototypes of such devices in which a Josephson phase shift is generated by coreless superconducting vortices. The smallness of the vortex allows a broad-range tunability by nanoscale manipulation of vortices in a micron-size array of vortex traps. We show that a phase shift in a device containing just a few vortex traps can be reconfigured between a large number of quantized states in a broad [−3π, +3π] range.
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| 25. |
- Grebenchuk, Sergey Yu, et al.
(författare)
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Observation of interacting Josephson vortex chains by magnetic force microscopy
- 2020
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Ingår i: Physical Review Research. - 2643-1564. ; 2:2
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Tidskriftsartikel (refereegranskat)abstract
- The ability to control Josephson vortices is instrumental for development of superconducting cryoelectronics. However, direct visualization of multivortex states in Josephson junctions is a challenging task. Here, we employ a magnetic force microscopy (MFM) for the analysis of planar Josephson junctions. We observe a specific MFM response, seen as a chain of small rings. By changing the applied field, we show that the number of rings is equal to the number of flux quanta in the junction. Therefore, each ring represents an individual vortex in a one-dimensional vortex chain within the junction. Our observation demonstrates that the MFM technique can be used for visualization of Josephson vortices and for probing their spatial configurations and mutual interaction.
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| 26. |
- Hartley, Philippa, et al.
(författare)
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SKA Science Data Challenge 2: analysis and results
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 523:2, s. 1967-1993
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Tidskriftsartikel (refereegranskat)abstract
- The Square Kilometre Array Observatory (SKAO) will explore the radio sky to new depths in order to conduct transformational science. SKAO data products made available to astronomers will be correspondingly large and complex, requiring the application of advanced analysis techniques to extract key science findings. To this end, SKAO is conducting a series of Science Data Challenges, each designed to familiarize the scientific community with SKAO data and to drive the development of new analysis techniques. We present the results from Science Data Challenge 2 (SDC2), which invited participants to find and characterize 233 245 neutral hydrogen (H i) sources in a simulated data product representing a 2000 h SKA-Mid spectral line observation from redshifts 0.25-0.5. Through the generous support of eight international supercomputing facilities, participants were able to undertake the Challenge using dedicated computational resources. Alongside the main challenge, 'reproducibility awards' were made in recognition of those pipelines which demonstrated Open Science best practice. The Challenge saw over 100 participants develop a range of new and existing techniques, with results that highlight the strengths of multidisciplinary and collaborative effort. The winning strategy - which combined predictions from two independent machine learning techniques to yield a 20 per cent improvement in overall performance - underscores one of the main Challenge outcomes: that of method complementarity. It is likely that the combination of methods in a so-called ensemble approach will be key to exploiting very large astronomical data sets.
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| 27. |
- Hedenmalm, Håkan, 1961-, et al.
(författare)
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Sharpening Holder's inequality
- 2018
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Ingår i: Journal of Functional Analysis. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0022-1236 .- 1096-0783. ; 275:5, s. 1280-1319
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Tidskriftsartikel (refereegranskat)abstract
- We strengthen Holder's inequality. The new family of sharp inequalities we obtain might be thought of as an analog of the Pythagorean theorem for the L-p-spaces. Our treatment of the subject matter is based on Bellman functions of four variables.
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| 28. |
- Salami, H., et al.
(författare)
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Spectroscopic observations, spin-orbit functions, and coupled-channel deperturbation analysis of data on the A (1)Sigma(+)(u) and b (3)Pi(u) states of Rb-2
- 2009
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 80:2
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Tidskriftsartikel (refereegranskat)abstract
- We present experimentally derived potential curves and spin-orbit interaction functions for the strongly perturbed A (1)Sigma(+)(u) and b (3)Pi(u) states of the rubidium dimer. The results are based on laser-induced fluorescence and optical-optical double-resonance polarization spectroscopy measurements combined with earlier laser-induced fluorescence data. We used an analytic potential (Hannover form) incorporated in a discrete variable representation of the Hamiltonian matrix for numerical energy-level calculation. A previous vibrational assignment of the A levels is confirmed, and very probable vibrational assignment for the b levels is also obtained. Currently, the rms residual of our fit is 0.053 cm(-1) as compared to the typical experimental uncertainties that are estimated to be 0.005 cm(-1). Fitted diagonal and off-diagonal spin-orbit functions are obtained and compared with ab initio calculations by all electrons and effective core pseudopotential methods. Analysis of the computational results yields an explanation for the ubiquitous single minima in these spin-orbit functions, which can be represented approximately by Morse-type functions.
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