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  1. Article ; Online: Chemically Accurate Potential Curves for H

    Volkmann, Hakon / Sathyanarayanan, Raamamurthy / Saenz, Alejandro / Jansen, Karl / Kühn, Stefan

    Journal of chemical theory and computation

    2024  Volume 20, Issue 3, Page(s) 1244–1251

    Abstract: With the recent advances in the development of devices capable of performing quantum computations, a growing interest in finding near-term applications has emerged in many areas of science. In the era of nonfault tolerant quantum devices, algorithms that ...

    Abstract With the recent advances in the development of devices capable of performing quantum computations, a growing interest in finding near-term applications has emerged in many areas of science. In the era of nonfault tolerant quantum devices, algorithms that only require comparably short circuits accompanied by high repetition rates are considered to be a promising approach for assisting classical machines with finding a solution on computationally hard problems. The ADAPT approach previously introduced in Nat. Commun.
    Language English
    Publishing date 2024-01-12
    Publishing country United States
    Document type Journal Article
    ISSN 1549-9626
    ISSN (online) 1549-9626
    DOI 10.1021/acs.jctc.3c01281
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Book: Quasi-Monte Carlo methods for lattice systems

    Jansen, Karl

    a first look

    (DESY ; 13,022)

    2013  

    Author's details K. Jansen ... Deutsches Elektronen-Synchrotron, DESY
    Series title DESY ; 13,022
    Language English
    Size 22 S, 30 cm
    Publisher DESY
    Publishing place Zeuthen ;Hamburg
    Document type Book
    Database Former special subject collection: coastal and deep sea fishing

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  3. Book: A first look at quasi-Monte Carlo for lattice field theory problems

    Jansen, Karl

    (DESY ; 12,211)

    2012  

    Author's details K. Jansen.Deutsches Elektronen-Synchrotron, DESY
    Series title DESY ; 12,211
    Language English
    Size [6] Bl, graph. Darst, 30 cm
    Publisher DESY
    Publishing place Zeuthen ;Hamburg
    Document type Book
    Database Former special subject collection: coastal and deep sea fishing

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  4. Article ; Online: Flavor Decomposition for the Proton Helicity Parton Distribution Functions.

    Alexandrou, Constantia / Constantinou, Martha / Hadjiyiannakou, Kyriakos / Jansen, Karl / Manigrasso, Floriano

    Physical review letters

    2021  Volume 126, Issue 10, Page(s) 102003

    Abstract: We present, for the first time, an ab initio calculation of the individual up, down, and strange quark helicity parton distribution functions for the proton. The calculation is performed within the twisted mass clover-improved fermion formulation of ... ...

    Abstract We present, for the first time, an ab initio calculation of the individual up, down, and strange quark helicity parton distribution functions for the proton. The calculation is performed within the twisted mass clover-improved fermion formulation of lattice QCD. The analysis is performed using one ensemble of dynamical up, down, strange, and charm quarks with a pion mass of 260 MeV. The lattice matrix elements are nonperturbatively renormalized and the final results are presented in the MS[over ¯] scheme at a scale of 2 GeV. We give results for Δu^{+}(x), Δd^{+}(x) Δu^{-}(x), Δd^{-}(x), including disconnected quark loop contributions, as well as for Δs^{+}(x) and Δs^{-}(x). For the latter we achieve unprecedented precision compared to the phenomenological estimates.
    Language English
    Publishing date 2021-03-30
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.126.102003
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Book ; Online: Detecting and Mitigating Mode-Collapse for Flow-based Sampling of Lattice Field Theories

    Nicoli, Kim A. / Anders, Christopher J. / Hartung, Tobias / Jansen, Karl / Kessel, Pan / Nakajima, Shinichi

    2023  

    Abstract: We study the consequences of mode-collapse of normalizing flows in the context of lattice field theory. Normalizing flows allow for independent sampling. For this reason, it is hoped that they can avoid the tunneling problem of local-update MCMC ... ...

    Abstract We study the consequences of mode-collapse of normalizing flows in the context of lattice field theory. Normalizing flows allow for independent sampling. For this reason, it is hoped that they can avoid the tunneling problem of local-update MCMC algorithms for multi-modal distributions. In this work, we first point out that the tunneling problem is also present for normalizing flows but is shifted from the sampling to the training phase of the algorithm. Specifically, normalizing flows often suffer from mode-collapse for which the training process assigns vanishingly low probability mass to relevant modes of the physical distribution. This may result in a significant bias when the flow is used as a sampler in a Markov-Chain or with Importance Sampling. We propose a metric to quantify the degree of mode-collapse and derive a bound on the resulting bias. Furthermore, we propose various mitigation strategies in particular in the context of estimating thermodynamic observables, such as the free energy.

    Comment: 10 pages, 7 figures, 6 pages of supplement material
    Keywords High Energy Physics - Lattice ; Computer Science - Machine Learning ; Physics - Computational Physics
    Publishing date 2023-02-27
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Book ; Online: Stout smearing for twisted mass fermions

    Jansen, Karl

    (DESY ; 07,157 ; Proceedings of Science)

    2007  

    Author's details Karl Jansen
    Series title DESY ; 07,157
    Proceedings of Science
    Language English
    Size Online-Ressource (7 S., 296 KB), graph. Darst
    Edition v1, 27 Sep 2007
    Publisher Technische Informationsbibliothek u. Universitätsbibliothek ; DESY
    Publishing place Hannover ; Zeuthen
    Document type Book ; Online
    Note Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden
    Database Library catalogue of the German National Library of Science and Technology (TIB), Hannover

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  7. Book: Stout smearing for twisted mass fermions

    Jansen, Karl

    (DESY ; 07,157)

    2007  

    Author's details K. Jansen
    Series title DESY ; 07,157
    Language English
    Size 7 S., graph. Darst., 30 cm
    Publisher DESY
    Publishing place Zeithen ;Hamburg
    Document type Book
    Database Library catalogue of the German National Library of Science and Technology (TIB), Hannover

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  8. Article: Causticum: Neue Wege zu einer alten Wahrheit

    Jansen, Karl Heinz / Quak, Dirk Thomas

    Allgemeine Homöopathische Zeitung

    2018  Volume 263, Issue 04, Page(s) 22–36

    Abstract: Das von Hahnemann beschriebene Arzneibild von Causticum ist, aufgrund der Vermischung der Symptome der „Tinctura acris sine kali“ mit denen des später in den chronischen Krankheiten beschriebenen Causticum-Destillats, bis heute mit Unsicherheiten belegt. ...

    Abstract Das von Hahnemann beschriebene Arzneibild von Causticum ist, aufgrund der Vermischung der Symptome der „Tinctura acris sine kali“ mit denen des später in den chronischen Krankheiten beschriebenen Causticum-Destillats, bis heute mit Unsicherheiten belegt. Aber auch die Substanzen, die bei Hahnemanns Causticum-Synthesen entstanden, sind chemisch nicht eindeutig definiert. Wir wiederholten deshalb mehrfach in einem modernen Forschungslabor Hahnemanns Herstellungsprozedur von Causticum unter verschiedenen Bedingungen und analysierten die Destillationen mit aufwendigen chemischen Untersuchungen, deren Ergebnisse wesentliche und neue Aspekte in die Diskussion bringen.
    Keywords Causticum ; Hydras caustici ; Silikate ; Ammoniumsilikate ; Spurenanalytik ; Causticum ; hydras caustici ; silicates ; ammonium silicates ; trace analysis
    Language German
    Publishing date 2018-07-01
    Publisher © Georg Thieme Verlag KG
    Publishing place Stuttgart ; New York
    Document type Article
    ZDB-ID 2124175-2
    ISSN 1439-8990 ; 1438-2563
    ISSN (online) 1439-8990
    ISSN 1438-2563
    DOI 10.1055/a-0628-5781
    Database Thieme publisher's database

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  9. Article: Die Entschlüsselung des Causticumrätsels

    Jansen, Karl Heinz / Quak, Dirk Thomas

    Homöopathie konkret

    2018  Volume -, Issue 1, Page(s) 20

    Language German
    Document type Article
    ZDB-ID 2430848-1
    ISSN 1866-8542
    Database Current Contents Medicine

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  10. Book ; Online: Multilevel Monte Carlo for quantum mechanics on a lattice

    Jansen, Karl / Müller, Eike Hermann / Scheichl, Robert

    2020  

    Abstract: Monte Carlo simulations of quantum field theories on a lattice become increasingly expensive as the continuum limit is approached since the cost per independent sample grows with a high power of the inverse lattice spacing. Simulations on fine lattices ... ...

    Abstract Monte Carlo simulations of quantum field theories on a lattice become increasingly expensive as the continuum limit is approached since the cost per independent sample grows with a high power of the inverse lattice spacing. Simulations on fine lattices suffer from critical slowdown, the rapid growth of autocorrelations in the Markov chain. This causes a strong increase in the number of lattice configurations that have to be generated to obtain statistically significant results. This paper discusses hierarchical sampling methods to tame the growth in autocorrelations. Combined with multilevel variance reduction, this significantly reduces the computational cost of simulations for given tolerances $\epsilon_{\text{disc}}$ on the discretisation error and $\epsilon_{\text{stat}}$ on the statistical error. For observables with lattice errors of order $\alpha$ and integrated autocorrelation times that grow like $\tau_{\mathrm{int}}\propto a^{-z}$, multilevel Monte Carlo (MLMC) reduces the cost from $\mathcal{O}(\epsilon_{\text{stat}}^{-2}\epsilon_{\text{disc}}^{-(1+z)/\alpha})$ to $\mathcal{O}(\epsilon_{\text{stat}}^{-2}\vert\log \epsilon_{\text{disc}} \vert^2+\epsilon_{\text{disc}}^{-1/\alpha})$ or $\mathcal{O}(\epsilon_{\text{stat}}^{-2}+\epsilon_{\text{disc}}^{-1/\alpha})$. Higher gains are expected for simulations of quantum field theories in $D$ dimensions. The efficiency of the approach is demonstrated on two model systems, including a topological oscillator that is badly affected by critical slowdown from topological charge freezing. On fine lattices, the new methods are orders of magnitude faster than standard Hybrid Monte Carlo sampling. For high resolutions, MLMC can be used to accelerate even the cluster algorithm for the topological oscillator. Performance is further improved through perturbative matching which guarantees efficient coupling of theories on the multilevel hierarchy.

    Comment: 23 pages, 17 figures, 5 tables
    Keywords High Energy Physics - Lattice ; Mathematics - Numerical Analysis ; Physics - Computational Physics ; 81-08 ; 81T25 ; 65Y20 ; 60J22 ; F.2 ; J.2
    Subject code 612
    Publishing date 2020-08-07
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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