--- _id: '14931' abstract: - lang: eng text: We prove an upper bound on the ground state energy of the dilute spin-polarized Fermi gas capturing the leading correction to the kinetic energy resulting from repulsive interactions. One of the main ingredients in the proof is a rigorous implementation of the fermionic cluster expansion of Gaudin et al. (1971) [15]. acknowledgement: A.B.L. would like to thank Johannes Agerskov and Jan Philip Solovej for valuable discussions. We thank Alessandro Giuliani for helpful discussions and for pointing out the reference [18]. Funding from the European Union's Horizon 2020 research and innovation programme under the ERC grant agreement No 694227 is acknowledged. Financial support by the Austrian Science Fund (FWF) through project number I 6427-N (as part of the SFB/TRR 352) is gratefully acknowledged. article_number: '110320' article_processing_charge: Yes (via OA deal) article_type: original author: - first_name: Asbjørn Bækgaard full_name: Lauritsen, Asbjørn Bækgaard id: e1a2682f-dc8d-11ea-abe3-81da9ac728f1 last_name: Lauritsen orcid: 0000-0003-4476-2288 - first_name: Robert full_name: Seiringer, Robert id: 4AFD0470-F248-11E8-B48F-1D18A9856A87 last_name: Seiringer orcid: 0000-0002-6781-0521 citation: ama: 'Lauritsen AB, Seiringer R. Ground state energy of the dilute spin-polarized Fermi gas: Upper bound via cluster expansion. Journal of Functional Analysis. 2024;286(7). doi:10.1016/j.jfa.2024.110320' apa: 'Lauritsen, A. B., & Seiringer, R. (2024). Ground state energy of the dilute spin-polarized Fermi gas: Upper bound via cluster expansion. Journal of Functional Analysis. Elsevier. https://doi.org/10.1016/j.jfa.2024.110320' chicago: 'Lauritsen, Asbjørn Bækgaard, and Robert Seiringer. “Ground State Energy of the Dilute Spin-Polarized Fermi Gas: Upper Bound via Cluster Expansion.” Journal of Functional Analysis. Elsevier, 2024. https://doi.org/10.1016/j.jfa.2024.110320.' ieee: 'A. B. Lauritsen and R. Seiringer, “Ground state energy of the dilute spin-polarized Fermi gas: Upper bound via cluster expansion,” Journal of Functional Analysis, vol. 286, no. 7. Elsevier, 2024.' ista: 'Lauritsen AB, Seiringer R. 2024. Ground state energy of the dilute spin-polarized Fermi gas: Upper bound via cluster expansion. Journal of Functional Analysis. 286(7), 110320.' mla: 'Lauritsen, Asbjørn Bækgaard, and Robert Seiringer. “Ground State Energy of the Dilute Spin-Polarized Fermi Gas: Upper Bound via Cluster Expansion.” Journal of Functional Analysis, vol. 286, no. 7, 110320, Elsevier, 2024, doi:10.1016/j.jfa.2024.110320.' short: A.B. Lauritsen, R. Seiringer, Journal of Functional Analysis 286 (2024). date_created: 2024-02-04T23:00:53Z date_published: 2024-01-24T00:00:00Z date_updated: 2024-03-28T10:54:02Z day: '24' department: - _id: RoSe doi: 10.1016/j.jfa.2024.110320 ec_funded: 1 external_id: arxiv: - '2301.04894' intvolume: ' 286' issue: '7' language: - iso: eng main_file_link: - open_access: '1' url: https://doi.org/10.1016/j.jfa.2024.110320 month: '01' oa: 1 oa_version: Published Version project: - _id: 25C6DC12-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '694227' name: Analysis of quantum many-body systems - _id: bda63fe5-d553-11ed-ba76-a16e3d2f256b grant_number: I06427 name: Mathematical Challenges in BCS Theory of Superconductivity publication: Journal of Functional Analysis publication_identifier: eissn: - 1096--0783 issn: - 0022-1236 publication_status: epub_ahead publisher: Elsevier quality_controlled: '1' scopus_import: '1' status: public title: 'Ground state energy of the dilute spin-polarized Fermi gas: Upper bound via cluster expansion' type: journal_article user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87 volume: 286 year: '2024' ... --- _id: '12183' abstract: - lang: eng text: We consider a gas of n bosonic particles confined in a box [−ℓ/2,ℓ/2]3 with Neumann boundary conditions. We prove Bose–Einstein condensation in the Gross–Pitaevskii regime, with an optimal bound on the condensate depletion. Moreover, our lower bound for the ground state energy in a small box [−ℓ/2,ℓ/2]3 implies (via Neumann bracketing) a lower bound for the ground state energy of N bosons in a large box [−L/2,L/2]3 with density ρ=N/L3 in the thermodynamic limit. acknowledgement: Funding from the European Union’s Horizon 2020 research and innovation programme under the ERC grant agreement No 694227 is gratefully acknowledged. article_processing_charge: No article_type: original author: - first_name: Chiara full_name: Boccato, Chiara id: 342E7E22-F248-11E8-B48F-1D18A9856A87 last_name: Boccato - first_name: Robert full_name: Seiringer, Robert id: 4AFD0470-F248-11E8-B48F-1D18A9856A87 last_name: Seiringer orcid: 0000-0002-6781-0521 citation: ama: Boccato C, Seiringer R. The Bose Gas in a box with Neumann boundary conditions. Annales Henri Poincare. 2023;24:1505-1560. doi:10.1007/s00023-022-01252-3 apa: Boccato, C., & Seiringer, R. (2023). The Bose Gas in a box with Neumann boundary conditions. Annales Henri Poincare. Springer Nature. https://doi.org/10.1007/s00023-022-01252-3 chicago: Boccato, Chiara, and Robert Seiringer. “The Bose Gas in a Box with Neumann Boundary Conditions.” Annales Henri Poincare. Springer Nature, 2023. https://doi.org/10.1007/s00023-022-01252-3. ieee: C. Boccato and R. Seiringer, “The Bose Gas in a box with Neumann boundary conditions,” Annales Henri Poincare, vol. 24. Springer Nature, pp. 1505–1560, 2023. ista: Boccato C, Seiringer R. 2023. The Bose Gas in a box with Neumann boundary conditions. Annales Henri Poincare. 24, 1505–1560. mla: Boccato, Chiara, and Robert Seiringer. “The Bose Gas in a Box with Neumann Boundary Conditions.” Annales Henri Poincare, vol. 24, Springer Nature, 2023, pp. 1505–60, doi:10.1007/s00023-022-01252-3. short: C. Boccato, R. Seiringer, Annales Henri Poincare 24 (2023) 1505–1560. date_created: 2023-01-15T23:00:52Z date_published: 2023-05-01T00:00:00Z date_updated: 2023-08-16T11:34:03Z day: '01' department: - _id: RoSe doi: 10.1007/s00023-022-01252-3 ec_funded: 1 external_id: arxiv: - '2205.15284' isi: - '000910751800002' intvolume: ' 24' isi: 1 language: - iso: eng main_file_link: - open_access: '1' url: https://doi.org/10.48550/arXiv.2205.15284 month: '05' oa: 1 oa_version: Preprint page: 1505-1560 project: - _id: 25C6DC12-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '694227' name: Analysis of quantum many-body systems publication: Annales Henri Poincare publication_identifier: issn: - 1424-0637 publication_status: published publisher: Springer Nature quality_controlled: '1' scopus_import: '1' status: public title: The Bose Gas in a box with Neumann boundary conditions type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 24 year: '2023' ... --- _id: '12430' abstract: - lang: eng text: We study the time evolution of the Nelson model in a mean-field limit in which N nonrelativistic bosons weakly couple (with respect to the particle number) to a positive or zero mass quantized scalar field. Our main result is the derivation of the Bogoliubov dynamics and higher-order corrections. More precisely, we prove the convergence of the approximate wave function to the many-body wave function in norm, with a convergence rate proportional to the number of corrections taken into account in the approximation. We prove an analogous result for the unitary propagator. As an application, we derive a simple system of partial differential equations describing the time evolution of the first- and second-order approximations to the one-particle reduced density matrices of the particles and the quantum field, respectively. article_number: '2350006' article_processing_charge: No article_type: original author: - first_name: Marco full_name: Falconi, Marco last_name: Falconi - first_name: Nikolai K full_name: Leopold, Nikolai K id: 4BC40BEC-F248-11E8-B48F-1D18A9856A87 last_name: Leopold orcid: 0000-0002-0495-6822 - first_name: David Johannes full_name: Mitrouskas, David Johannes id: cbddacee-2b11-11eb-a02e-a2e14d04e52d last_name: Mitrouskas - first_name: Sören P full_name: Petrat, Sören P id: 40AC02DC-F248-11E8-B48F-1D18A9856A87 last_name: Petrat orcid: 0000-0002-9166-5889 citation: ama: Falconi M, Leopold NK, Mitrouskas DJ, Petrat SP. Bogoliubov dynamics and higher-order corrections for the regularized Nelson model. Reviews in Mathematical Physics. 2023;35(4). doi:10.1142/S0129055X2350006X apa: Falconi, M., Leopold, N. K., Mitrouskas, D. J., & Petrat, S. P. (2023). Bogoliubov dynamics and higher-order corrections for the regularized Nelson model. Reviews in Mathematical Physics. World Scientific Publishing. https://doi.org/10.1142/S0129055X2350006X chicago: Falconi, Marco, Nikolai K Leopold, David Johannes Mitrouskas, and Sören P Petrat. “Bogoliubov Dynamics and Higher-Order Corrections for the Regularized Nelson Model.” Reviews in Mathematical Physics. World Scientific Publishing, 2023. https://doi.org/10.1142/S0129055X2350006X. ieee: M. Falconi, N. K. Leopold, D. J. Mitrouskas, and S. P. Petrat, “Bogoliubov dynamics and higher-order corrections for the regularized Nelson model,” Reviews in Mathematical Physics, vol. 35, no. 4. World Scientific Publishing, 2023. ista: Falconi M, Leopold NK, Mitrouskas DJ, Petrat SP. 2023. Bogoliubov dynamics and higher-order corrections for the regularized Nelson model. Reviews in Mathematical Physics. 35(4), 2350006. mla: Falconi, Marco, et al. “Bogoliubov Dynamics and Higher-Order Corrections for the Regularized Nelson Model.” Reviews in Mathematical Physics, vol. 35, no. 4, 2350006, World Scientific Publishing, 2023, doi:10.1142/S0129055X2350006X. short: M. Falconi, N.K. Leopold, D.J. Mitrouskas, S.P. Petrat, Reviews in Mathematical Physics 35 (2023). date_created: 2023-01-29T23:00:59Z date_published: 2023-01-09T00:00:00Z date_updated: 2023-08-16T11:47:27Z day: '09' department: - _id: RoSe doi: 10.1142/S0129055X2350006X external_id: arxiv: - '2110.00458' isi: - '000909760300001' intvolume: ' 35' isi: 1 issue: '4' language: - iso: eng main_file_link: - open_access: '1' url: ' https://doi.org/10.48550/arXiv.2110.00458' month: '01' oa: 1 oa_version: Preprint publication: Reviews in Mathematical Physics publication_identifier: issn: - 0129-055X publication_status: published publisher: World Scientific Publishing quality_controlled: '1' scopus_import: '1' status: public title: Bogoliubov dynamics and higher-order corrections for the regularized Nelson model type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 35 year: '2023' ... --- _id: '14374' abstract: - lang: eng text: "Superconductivity has many important applications ranging from levitating trains over qubits to MRI scanners. The phenomenon is successfully modeled by Bardeen-Cooper-Schrieffer (BCS) theory. From a mathematical perspective, BCS theory has been studied extensively for systems without boundary. However, little is known in the presence of boundaries. With the help of numerical methods physicists observed that the critical temperature may increase in the presence of a boundary. The goal of this thesis is to understand the influence of boundaries on the critical temperature in BCS theory and to give a first rigorous justification of these observations. On the way, we also study two-body Schrödinger operators on domains with boundaries and prove additional results for superconductors without boundary.\r\n\r\nBCS theory is based on a non-linear functional, where the minimizer indicates whether the system is superconducting or in the normal, non-superconducting state. By considering the Hessian of the BCS functional at the normal state, one can analyze whether the normal state is possibly a minimum of the BCS functional and estimate the critical temperature. The Hessian turns out to be a linear operator resembling a Schrödinger operator for two interacting particles, but with more complicated kinetic energy. As a first step, we study the two-body Schrödinger operator in the presence of boundaries.\r\nFor Neumann boundary conditions, we prove that the addition of a boundary can create new eigenvalues, which correspond to the two particles forming a bound state close to the boundary.\r\n\r\nSecond, we need to understand superconductivity in the translation invariant setting. While in three dimensions this has been extensively studied, there is no mathematical literature for the one and two dimensional cases. In dimensions one and two, we compute the weak coupling asymptotics of the critical temperature and the energy gap in the translation invariant setting. We also prove that their ratio is independent of the microscopic details of the model in the weak coupling limit; this property is referred to as universality.\r\n\r\nIn the third part, we study the critical temperature of superconductors in the presence of boundaries. We start by considering the one-dimensional case of a half-line with contact interaction. Then, we generalize the results to generic interactions and half-spaces in one, two and three dimensions. Finally, we compare the critical temperature of a quarter space in two dimensions to the critical temperatures of a half-space and of the full space." alternative_title: - ISTA Thesis article_processing_charge: No author: - first_name: Barbara full_name: Roos, Barbara id: 5DA90512-D80F-11E9-8994-2E2EE6697425 last_name: Roos orcid: 0000-0002-9071-5880 citation: ama: Roos B. Boundary superconductivity in BCS theory. 2023. doi:10.15479/at:ista:14374 apa: Roos, B. (2023). Boundary superconductivity in BCS theory. Institute of Science and Technology Austria. https://doi.org/10.15479/at:ista:14374 chicago: Roos, Barbara. “Boundary Superconductivity in BCS Theory.” Institute of Science and Technology Austria, 2023. https://doi.org/10.15479/at:ista:14374. ieee: B. Roos, “Boundary superconductivity in BCS theory,” Institute of Science and Technology Austria, 2023. ista: Roos B. 2023. Boundary superconductivity in BCS theory. Institute of Science and Technology Austria. mla: Roos, Barbara. Boundary Superconductivity in BCS Theory. Institute of Science and Technology Austria, 2023, doi:10.15479/at:ista:14374. short: B. Roos, Boundary Superconductivity in BCS Theory, Institute of Science and Technology Austria, 2023. date_created: 2023-09-28T14:23:04Z date_published: 2023-09-30T00:00:00Z date_updated: 2023-10-27T10:37:30Z day: '30' ddc: - '515' - '539' degree_awarded: PhD department: - _id: GradSch - _id: RoSe doi: 10.15479/at:ista:14374 ec_funded: 1 file: - access_level: open_access checksum: ef039ffc3de2cb8dee5b14110938e9b6 content_type: application/pdf creator: broos date_created: 2023-10-06T11:35:56Z date_updated: 2023-10-06T11:35:56Z file_id: '14398' file_name: phd-thesis-draft_pdfa_acrobat.pdf file_size: 2365702 relation: main_file - access_level: closed checksum: 81dcac33daeefaf0111db52f41bb1fd0 content_type: application/x-zip-compressed creator: broos date_created: 2023-10-06T11:38:01Z date_updated: 2023-10-06T11:38:01Z file_id: '14399' file_name: Version5.zip file_size: 4691734 relation: source_file file_date_updated: 2023-10-06T11:38:01Z has_accepted_license: '1' language: - iso: eng license: https://creativecommons.org/licenses/by-nc-sa/4.0/ month: '09' oa: 1 oa_version: Published Version page: '206' project: - _id: 25C6DC12-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '694227' name: Analysis of quantum many-body systems - _id: bda63fe5-d553-11ed-ba76-a16e3d2f256b grant_number: I06427 name: Mathematical Challenges in BCS Theory of Superconductivity publication_identifier: issn: - 2663 - 337X publication_status: published publisher: Institute of Science and Technology Austria related_material: record: - id: '13207' relation: part_of_dissertation status: public - id: '10850' relation: part_of_dissertation status: public status: public supervisor: - first_name: Robert full_name: Seiringer, Robert id: 4AFD0470-F248-11E8-B48F-1D18A9856A87 last_name: Seiringer orcid: 0000-0002-6781-0521 title: Boundary superconductivity in BCS theory tmp: image: /images/cc_by_nc_sa.png legal_code_url: https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode name: Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) short: CC BY-NC-SA (4.0) type: dissertation user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9 year: '2023' ... --- _id: '13207' abstract: - lang: eng text: We consider the linear BCS equation, determining the BCS critical temperature, in the presence of a boundary, where Dirichlet boundary conditions are imposed. In the one-dimensional case with point interactions, we prove that the critical temperature is strictly larger than the bulk value, at least at weak coupling. In particular, the Cooper-pair wave function localizes near the boundary, an effect that cannot be modeled by effective Neumann boundary conditions on the order parameter as often imposed in Ginzburg–Landau theory. We also show that the relative shift in critical temperature vanishes if the coupling constant either goes to zero or to infinity. acknowledgement: We thank Egor Babaev for encouraging us to study this problem, and Rupert Frank for many fruitful discussions. scussions. Funding. Funding from the European Union’s Horizon 2020 research and innovation programme under the ERC grant agreement No. 694227 (Barbara Roos and Robert Seiringer) is gratefully acknowledged. article_processing_charge: No article_type: original author: - first_name: Christian full_name: Hainzl, Christian last_name: Hainzl - first_name: Barbara full_name: Roos, Barbara id: 5DA90512-D80F-11E9-8994-2E2EE6697425 last_name: Roos orcid: 0000-0002-9071-5880 - first_name: Robert full_name: Seiringer, Robert id: 4AFD0470-F248-11E8-B48F-1D18A9856A87 last_name: Seiringer orcid: 0000-0002-6781-0521 citation: ama: Hainzl C, Roos B, Seiringer R. Boundary superconductivity in the BCS model. Journal of Spectral Theory. 2023;12(4):1507–1540. doi:10.4171/JST/439 apa: Hainzl, C., Roos, B., & Seiringer, R. (2023). Boundary superconductivity in the BCS model. Journal of Spectral Theory. EMS Press. https://doi.org/10.4171/JST/439 chicago: Hainzl, Christian, Barbara Roos, and Robert Seiringer. “Boundary Superconductivity in the BCS Model.” Journal of Spectral Theory. EMS Press, 2023. https://doi.org/10.4171/JST/439. ieee: C. Hainzl, B. Roos, and R. Seiringer, “Boundary superconductivity in the BCS model,” Journal of Spectral Theory, vol. 12, no. 4. EMS Press, pp. 1507–1540, 2023. ista: Hainzl C, Roos B, Seiringer R. 2023. Boundary superconductivity in the BCS model. Journal of Spectral Theory. 12(4), 1507–1540. mla: Hainzl, Christian, et al. “Boundary Superconductivity in the BCS Model.” Journal of Spectral Theory, vol. 12, no. 4, EMS Press, 2023, pp. 1507–1540, doi:10.4171/JST/439. short: C. Hainzl, B. Roos, R. Seiringer, Journal of Spectral Theory 12 (2023) 1507–1540. date_created: 2023-07-10T16:35:45Z date_published: 2023-05-18T00:00:00Z date_updated: 2023-10-27T10:37:29Z day: '18' ddc: - '530' department: - _id: GradSch - _id: RoSe doi: 10.4171/JST/439 ec_funded: 1 external_id: arxiv: - '2201.08090' isi: - '000997933500008' file: - access_level: open_access checksum: 5501da33be010b5c81440438287584d5 content_type: application/pdf creator: alisjak date_created: 2023-07-11T08:19:15Z date_updated: 2023-07-11T08:19:15Z file_id: '13208' file_name: 2023_EMS_Hainzl.pdf file_size: 304619 relation: main_file success: 1 file_date_updated: 2023-07-11T08:19:15Z has_accepted_license: '1' intvolume: ' 12' isi: 1 issue: '4' language: - iso: eng license: https://creativecommons.org/licenses/by/4.0/ month: '05' oa: 1 oa_version: Published Version page: 1507–1540 project: - _id: 25C6DC12-B435-11E9-9278-68D0E5697425 call_identifier: H2020 grant_number: '694227' name: Analysis of quantum many-body systems publication: Journal of Spectral Theory publication_identifier: eissn: - 1664-0403 issn: - 1664-039X publication_status: published publisher: EMS Press quality_controlled: '1' related_material: record: - id: '14374' relation: dissertation_contains status: public status: public title: Boundary superconductivity in the BCS model tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8 volume: 12 year: '2023' ...