| 1. |
- Forssen, Christian, 1974, et al.
(författare)
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The Ab Initio No-core Shell Model
- 2009
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 1432-5411 .- 0177-7963. ; 45:2, s. 111-
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Konferensbidrag (refereegranskat)abstract
- This contribution reviews a number of applications of the ab initio no-core shell model (NCSM) within nuclear physics and beyond. We will highlight a nuclear-structure study of the A = 12 isobar using a chiral NN + 3NF interaction. In the spirit of this workshop we will also mention the new development of the NCSM formalism to describe open channels and to approach the problem of nuclear reactions. Finally, we will illustrate the universality of the many-body problem by presenting the recent adaptation of the NCSM effective-interaction approach to study the many-boson problem in an external trapping potential with short-range interactions.This article is based on the presentation by C. Forssén at the Fifth Workshop on Critical Stability, Erice, Sicily.
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| 2. |
- Peralle, Cindy, 1993, et al.
(författare)
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Monolithic cavity for optomechanics featuring a bound state in the continuum
- 2023
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Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023.
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Konferensbidrag (refereegranskat)abstract
- Due to their low mass and high reflectivity, photonic-crystal membranes are excellent candidates for vibrating end mirrors in optomechanical cavities. Cavities with photonic-crystal membranes can support a quasi-bound state in the continuum (BIC), i.e., a resonance exhibiting an optical quality factor only limited by dissipative loss. Such cavities promise to access new regimes in optomechanics [1], e.g., the single-photon strong-coupling regime for applications in precision sensing [2] and quantum information processing [3]. However, previously proposed designs turned out to be difficult to fabricate with state-of-the-art nanolithography techniques. Furthermore, it is difficult to find new nanophotonic structures with a bound state in the continuum, in particular if a substrate breaks the mirror symmetry of the cavity.
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| 3. |
- Pankin, A. Y., et al.
(författare)
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UNDERSTANDING AND PREDICTION OF INTERNAL TRANSPORT BARRIERS IN TOKAMAKS USING INTEGRATED MODELING
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Internal transport barriers (ITBs) are regions of plasmas in tokamak discharges with strongly reduced anomalous transport. The ITB formation can lead to the improvement of energy and particle confinement. Some advanced tokamak scenarios rely on the ITB formation in the plasma core. In particular, the high beta poloidal scenario that has been recently studied on the DIII-D and EAST tokamaks depends on the ITB formation at large radii 1 . It is generally believed that ITBs are triggered by a large ExB flow shear and by a small or reversed magnetic shear. However, the analysis of DIII-D experimental data shows that the ExB flow shear plays a small role in the ITB formation in high β p discharges. Using the integrated modeling approach, we demonstrate that the ITBs in these discharges require a combination of large Shafranov shift and reversed magnetic shear. The ExB flow shear indeed does not play a role in the ITB triggering. In addition, it is demonstrated that the ITB formation depends on the q profiles. An increased plasma current can result in a disappearance of ITB. The dependences of ITB on the Shafranov shift, magnetic shear, and q-profiles can be explained from the analysis of the anomalous transport in high beta poloidal discharges. Theory-based Weiland transport model 2 that predict the anomalous transport driven by ion-temperature gradient driven modes, trapped electron modes and some other MHD modes shows a significant quenching effect from the Shafranov shift. The q-profiles are also found important for the formation of transport barriers in the high beta poloidal DIII-D discharges. The gyro-kinetic GTC simulation confirms the anomalous transport trends observed with the theory-based Weiland model. The observed requirements for the ITB formation can be used in the integrated predictive modeling to optimize the high beta poloidal discharge scenarios in DIII-D, EAST and other tokamaks.
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| 4. |
- Tanaka, Kei E. I., et al.
(författare)
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Multiple Feedback in Low-Metallicity Massive Star Formation
- 2019
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 14:S344, s. 190-194
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Konferensbidrag (refereegranskat)abstract
- We theoretically investigate the impact of feedback and its metallicity dependence in massive star formation from prestellar cores at all metallicity range. We include the feedback by MHD disk winds, radiation pressure, and photoevaporation solving the evolution of protostars and accretion flows self-consistently. Interestingly, we find that the feedback does not set the upper mass limit of stellar birth mass at any metallicity. At the solar metallicity, the MHD disk wind is the dominant feedback to set the star formation efficiencies (SFEs) from the prestellar cores similar to low-mass star formation. The SFE is found to be lower at lower surface density environment. The photoevaporation becomes significant at the low metallicity of Z < 10(-2) Z(circle dot). Considering this efficient photoevaporation, we conclude that the IMF slope is steeper, i.e., massive stars are rarer at the extremely metal-poor environment of 10(-5)-10(-3)Z(circle dot). Our study raises a question on the common assumption of the universal IMF with a truncated at 100M(circle dot). Since the total feedback strength in the cluster/galaxy scale is sensitive to the number fraction of massive stars, the re-evaluations of IMF at various environments are necessary.
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| 5. |
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| 6. |
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| 7. |
- Chang, Tsu Chi, et al.
(författare)
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Lasing Action in GaN-Based VCSELs with top High-Contrast Grating Reflectors
- 2018
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Ingår i: Conference Digest - IEEE International Semiconductor Laser Conference. - 0899-9406. ; 2018-September, s. 191-192
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Konferensbidrag (refereegranskat)abstract
- We report a GaN-based VCSEL with a high-contrast grating (HCG) as the top mirror. The HCG consisted of TiO2 and rested directly on the n-GaN without an airgap or the use of any DBR layers to boost the reflectivity. The full VCSEL structure was optically pumped at room temperature and showed a lasing threshold of approximately 0.99 MW/cm2 and a lasing wavelength at 369.8 nm. The demonstration of HCG GaN-based VCSEL opens up the possibility to explore all the potential benefits of HCGs in the blue and ultraviolet spectral regime.
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| 8. |
- Ciers, Anastasiia, 1992, et al.
(författare)
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Integrated free-space optomechanics with AlGaAs heterostructures
- 2021
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Ingår i: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We fabricated and characterized suspended bi-layered photonic crystal slabs in AlGaAs heterostructures. Our approach allows to create integrated, closely spaced membranes, which can exhibit photonic bound states in the continuum to increase light-matter interaction.
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| 9. |
- Frigerio, Jacopo, et al.
(författare)
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Mid-infrared second harmonic generation in Ge/SiGe coupled quantum wells
- 2020
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Ingår i: 2020 IEEE Photonics Conference, IPC 2020 - Proceedings. ; September 2020
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Konferensbidrag (refereegranskat)abstract
- We present the theoretical investigation and the experimental demonstration of second harmonic generation in the mid-infrared by hole-doped Ge/SiGe asymmetric quantum wells.
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| 10. |
- Frigerio, Jacopo, et al.
(författare)
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Mid-infrared second harmonic generation with Ge quantum wells
- 2021
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Ingår i: IEEE International Conference on Group IV Photonics GFP. - 1949-2081. ; 2021-December
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Konferensbidrag (refereegranskat)abstract
- We present the experimental demonstration of second harmonic generation in the mid-infrared by hole-doped Ge/SiGe asymmetric quantum wells.
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