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  1. Article ; Online: Synchronization in epidemic growth and the impossibility of selective containment.

    Budich, Jan C / Bergholtz, Emil J

    Mathematical medicine and biology : a journal of the IMA

    2021  Volume 38, Issue 4, Page(s) 467–473

    Abstract: Containment, aiming to prevent the epidemic stage of community-spreading altogether, and mitigation, aiming to merely 'flatten the curve' of a wide-ranged outbreak, constitute two qualitatively different approaches to combating an epidemic through non- ... ...

    Abstract Containment, aiming to prevent the epidemic stage of community-spreading altogether, and mitigation, aiming to merely 'flatten the curve' of a wide-ranged outbreak, constitute two qualitatively different approaches to combating an epidemic through non-pharmaceutical interventions. Here, we study a simple model of epidemic dynamics separating the population into two groups, namely a low-risk group and a high-risk group, for which different strategies are pursued. Due to synchronization effects, we find that maintaining a slower epidemic growth behaviour for the high-risk group is unstable against any finite coupling between the two groups. More precisely, the density of infected individuals in the two groups qualitatively evolves very similarly, apart from a small time delay and an overall scaling factor quantifying the coupling between the groups. Hence, selective containment of the epidemic in a targeted (high-risk) group is practically impossible whenever the surrounding society implements a mitigated community-spreading. We relate our general findings to the ongoing COVID-19 pandemic.
    MeSH term(s) COVID-19 ; Humans ; Pandemics ; Risk Factors ; SARS-CoV-2
    Language English
    Publishing date 2021-10-25
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2119786-6
    ISSN 1477-8602 ; 0265-0746 ; 1477-8599
    ISSN (online) 1477-8602
    ISSN 0265-0746 ; 1477-8599
    DOI 10.1093/imammb/dqab013
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Cologne/Königswinter

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    bis Jg. 2021: Bestellungen von Artikeln über das Online-Bestellformular
    ab Jg. 2022: Lesesaal (EG)

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  2. Article ; Online: Dynamically Induced Exceptional Phases in Quenched Interacting Semimetals.

    Lehmann, Carl / Schüler, Michael / Budich, Jan Carl

    Physical review letters

    2021  Volume 127, Issue 10, Page(s) 106601

    Abstract: We report on the dynamical formation of exceptional degeneracies in basic correlation functions of nonintegrable one- and two-dimensional systems quenched to the vicinity of a critical point. Remarkably, fine-tuned semimetallic points in the phase ... ...

    Abstract We report on the dynamical formation of exceptional degeneracies in basic correlation functions of nonintegrable one- and two-dimensional systems quenched to the vicinity of a critical point. Remarkably, fine-tuned semimetallic points in the phase diagram of the considered systems are thereby promoted to topologically robust non-Hermitian (NH) nodal phases emerging in the coherent time evolution of a dynamically equilibrating system. Using nonequilibrium Green's function methods within the conserving second Born approximation, we predict observable signatures of these NH nodal phases both in equilibrated spectral functions and in the nonequilibrium dynamics of momentum distribution functions.
    Language English
    Publishing date 2021-05-31
    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.127.106601
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    In stock of ZB MED Bonn / Germany

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  3. Article ; Online: Entanglement transfer from electrons to photons in quantum dots: an open quantum system approach.

    Budich, Jan C / Trauzettel, Björn

    Nanotechnology

    2010  Volume 21, Issue 27, Page(s) 274001

    Abstract: We investigate entanglement transfer from a system of two spin-entangled electron-hole pairs, each placed in a separate single mode cavity, to the photons emitted due to cavity leakage. Dipole selection rules and a splitting between the light hole and ... ...

    Abstract We investigate entanglement transfer from a system of two spin-entangled electron-hole pairs, each placed in a separate single mode cavity, to the photons emitted due to cavity leakage. Dipole selection rules and a splitting between the light hole and the heavy hole subbands are the crucial ingredients establishing a one-to-one correspondence between electron spins and circular photon polarizations. To account for the measurement of the photons as well as dephasing effects, we choose a stochastic Schrödinger equation and a conditional master equation approach, respectively. The influence of interactions with the environment as well as asymmetries in the coherent couplings on the photon entanglement is analysed for two concrete measurement schemes. The first one is designed to violate the Clauser-Horne-Shimony-Holt (CHSH) inequality, while the second one employs the visibility of interference fringes to prove the entanglement of the photons. Because of the spatial separation of the entangled electronic system over two quantum dots, a successful verification of entangled photons emitted by this system would imply the detection of nonlocal spin entanglement of massive particles in a solid state structure.
    Language English
    Publishing date 2010-07-09
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1362365-5
    ISSN 1361-6528 ; 0957-4484
    ISSN (online) 1361-6528
    ISSN 0957-4484
    DOI 10.1088/0957-4484/21/27/274001
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  4. Article ; Online: Topological aspects of π phase winding junctions in superconducting wires.

    Spånslätt, Christian / Ardonne, Eddy / Budich, Jan Carl / Hansson, T H

    Journal of physics. Condensed matter : an Institute of Physics journal

    2015  Volume 27, Issue 40, Page(s) 405701

    Abstract: We theoretically investigate Josephson junctions with a phase shift of π in various proximity induced one-dimensional superconductor models. One of the salient experimental signatures of topological superconductors, namely the fractionalized 4π periodic ... ...

    Abstract We theoretically investigate Josephson junctions with a phase shift of π in various proximity induced one-dimensional superconductor models. One of the salient experimental signatures of topological superconductors, namely the fractionalized 4π periodic Josephson effect, is closely related to the occurrence of a characteristic zero energy bound state in such junctions. We make a detailed analysis of a more general type of π-junctions coined 'phase winding junctions' where the phase of the order parameter rotates by an angle π while its absolute value is kept finite. Such junctions have different properties, also from a topological viewpoint, and there are no protected zero energy modes. We compare the phenomenology of such junctions in topological (p-wave) and trivial (s-wave) superconducting wires, and briefly discuss possible experimental probes. Furthermore, we propose a topological field theory that gives a minimal description of a wire with defects corresponding to π-junctions. This effective theory is a one-dimensional version of similar theories describing Majorana bound states in half-vortices of two-dimensional topological superconductors.
    Language English
    Publishing date 2015-10-14
    Publishing country England
    Document type Journal Article
    ZDB-ID 1472968-4
    ISSN 1361-648X ; 0953-8984
    ISSN (online) 1361-648X
    ISSN 0953-8984
    DOI 10.1088/0953-8984/27/40/405701
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  5. Book ; Online: Tunable quantum spin Hall effect in double quantum wells

    Michetti, Paolo / Budich, Jan C. / Novik, Elena G. / Recher, Patrik

    2011  

    Abstract: The field of topological insulators (TIs) is rapidly growing. Concerning possible applications, the search for materials with an easily controllable TI phase is a key issue. The quantum spin Hall effect, characterized by a single pair of helical edge ... ...

    Abstract The field of topological insulators (TIs) is rapidly growing. Concerning possible applications, the search for materials with an easily controllable TI phase is a key issue. The quantum spin Hall effect, characterized by a single pair of helical edge modes protected by time-reversal symmetry, has been demonstrated in HgTe-based quantum wells (QWs) with an inverted bandgap. We analyze the topological properties of a generically coupled HgTe-based double QW (DQW) and show how in such a system a TI phase can be driven by an inter-layer bias voltage, even when the individual layers are non-inverted. We argue, that this system allows for similar (layer-)pseudospin based physics as in bilayer graphene but with the crucial absence of a valley degeneracy.

    Comment: 9 pages, 8 figures, extended version (accepted Phys. Rev. B)
    Keywords Condensed Matter - Mesoscale and Nanoscale Physics ; Condensed Matter - Materials Science
    Publishing date 2011-07-20
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Book ; Online: Observation of a dynamical topological phase transition

    Fläschner, Nick / Vogel, Dominik / Tarnowski, Matthias / Rem, Benno S. / Lühmann, Dirk-Sören / Heyl, Markus / Budich, Jan Carl / Mathey, Ludwig / Sengstock, Klaus / Weitenberg, Christof

    2016  

    Abstract: Phase transitions are a fundamental concept in science describing diverse phenomena ranging from, e.g., the freezing of water to Bose-Einstein condensation. While the concept is well-established in equilibrium, similarly fundamental concepts for systems ... ...

    Abstract Phase transitions are a fundamental concept in science describing diverse phenomena ranging from, e.g., the freezing of water to Bose-Einstein condensation. While the concept is well-established in equilibrium, similarly fundamental concepts for systems far from equilibrium are just being explored, such as the recently introduced dynamical phase transition (DPT). Here we report on the first observation of a DPT in the dynamics of a fermionic many-body state after a quench between two lattice Hamiltonians. With time-resolved state tomography in a system of ultracold atoms in optical lattices, we obtain full access to the evolution of the wave function. We observe the appearance, movement, and annihilation of vortices in reciprocal space. We identify their number as a dynamical topological order parameter, which suddenly changes its value at the critical times of the DPT. Our observation of a DPT is an important step towards a more comprehensive understanding of non-equilibrium dynamics in general.
    Keywords Condensed Matter - Quantum Gases ; Condensed Matter - Mesoscale and Nanoscale Physics ; Quantum Physics
    Subject code 612
    Publishing date 2016-08-19
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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