Approximating local observables on projected entangled pair states

Tensor network states are for good reasons believed to capture ground states of gapped local Hamiltonians arising in the condensed matter context, states which are in turn expected to satisfy an entanglement area law. However, the computational hardness of contracting projected entangled pair states in two and higher dimensional systems is often seen as a significant obstacle when devising higher-dimensional variants of the density-matrix renormalisation group method. In this work, we show that for those projected entangled pair states that are expected to provide good approximations of such ground states of local Hamiltonians, one can compute local expectation values in quasi-polynomial time. We therefore provide a complexity-theoretic justification of why state-of-the-art numerical tools work so well in practice. We comment on how the transfer operators of such projected entangled pair states have a gap and discuss notions of local topological quantum order. We finally turn to the computation of local expectation values on quantum computers, providing a meaningful application for a small-scale quantum computer.Comment: 7 pages, 1 figure, minor changes in v

Duality Symmetry in the Schwarz-Sen Model

The continuous extension of the discrete duality symmetry of the Schwarz-Sen model is studied. The corresponding infinitesimal generator $Q$ turns out to be local, gauge invariant and metric independent. Furthermore, $Q$ commutes with all the conformal group generators. We also show that $Q$ is equivalent to the non---local duality transformation generator found in the Hamiltonian formulation of Maxwell theory. We next consider the Batalin--Fradkin-Vilkovisky formalism for the Maxwell theory and demonstrate that requiring a local duality transformation lead us to the Schwarz--Sen formulation. The partition functions are shown to be the same which implies the quantum equivalence of the two approaches.Comment: 10 pages, latex, small changes, final version to appear in Phys. Rev.

Zero-Mode Dynamics of String Webs

At sufficiently low energy the dynamics of a string web is dominated by zero modes involving rigid motion of the internal strings. The dimension of the associated moduli space equals the maximal number of internal faces in the web. The generic web moduli space has boundaries and multiple branches, and for webs with three or more faces the geometry is curved. Webs can also be studied in a lift to M-theory, where a string web is replaced by a membrane wrapped on a holomorphic curve in spacetime. In this case the moduli space is complexified and admits a Kaehler metric.Comment: LaTeX, 17 pages, 5 eps figures; v2: references adde

Intertwining Laplace Transformations of Linear Partial Differential Equations

We propose a generalization of Laplace transformations to the case of linear partial differential operators (LPDOs) of arbitrary order in R^n. Practically all previously proposed differential transformations of LPDOs are particular cases of this transformation (intertwining Laplace transformation, ILT). We give a complete algorithm of construction of ILT and describe the classes of operators in R^n suitable for this transformation. Keywords: Integration of linear partial differential equations, Laplace transformation, differential transformationComment: LaTeX, 25 pages v2: minor misprints correcte

String Network and U-Duality

We discuss the generalization of recently discovered BPS configurations, corresponding to the planar string networks, to non-planar ones by considering the U-duality symmetry of type II string theory in various dimensions. As an explicit example, we analyze the string solutions in 8-dimensional space-time, carrying SL(3) charges, and show that by aligning the strings along various directions appropriately, one can obtain a string network which preserves 1/8 supersymmetry.Comment: 8 pages, latex, references added, minor modification

Evaluation of the Lidar/Radiometer Inversion Code (LIRIC) to determine microphysical properties of volcanic and desert dust

© Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 LicenseThe Lidar/Radiometer Inversion Code (LIRIC) combines the multiwavelength lidar technique with sun/sky photometry and allows us to retrieve vertical profiles of particle optical and microphysical properties separately for fine-mode and coarse-mode particles. After a brief presentation of the theoretical background, we evaluate the potential of LIRIC to retrieve the optical and microphysical properties of irregularly shaped dust particles. The method is applied to two very different aerosol scenarios: a strong Saharan dust outbreak towards central Europe and an Eyjafjallajökull volcanic dust event. LIRIC profiles of particle mass concentrations for the coarse-mode as well as for the non-spherical particle fraction are compared with results for the non-spherical particle fraction as obtained with the polarization-lidar- based POLIPHON method. Similar comparisons for fine-mode and spherical particle fractions are presented also. Acceptable agreement between the different dust mass concentration profiles is obtained. LIRIC profiles of optical properties such as particle backscatter coefficient, lidar ratio, Ångström exponent, and particle depolarization ratio are compared with direct Raman lidar observations. Systematic deviations between the LIRIC retrieval products and the Raman lidar measurements of the desert dust lidar ratio, depolarization ratio, and spectral dependencies of particle backscatter and lidar ratio point to the applied spheroidal-particle model as main source for these uncertainties in the LIRIC results.Peer reviewe

« C’est normal qu’on mollisse ou qu’on vieillisse » : faut-il aborder le déclin fonctionnel avec les personnes âgées en médecine de famille ?

Pour répondre au vieillissement de la population, des initiatives de dépistage et de prise en charge des problèmes de santé liés à l’âge sont mises en place, notamment en médecine de famille. Les résultats préliminaires d’une étude qualitative suggèrent que les personnes âgées sont ambivalentes face à la notion d’anticipation des problèmes, tendent à les banaliser et à être réticentes à en parler spontanément à leur médecin. Cependant, elles trouvent pertinent que ce dernier aborde le sujet avec des questions spécifiques, ceci permettant d’initier une discussion sur des problématiques sensibles. Les possibilités de prise en charge des syndromes gériatriques et du déclin fonctionnel semblent peu connues des patient-e-s. Le dépistage permet donc d’aborder ces problématiques et d’informer les patient-e-s au sujet de solutions existantes. [Among the health strategies to respond to the aging of the population, initiatives for the screening and management of age-related health issues are implemented, including in family medicine. Preliminary results of a qualitative study suggest that elderly people are ambivalent about anticipating age-related issues, tend to trivialize them and to be reluctant to discuss them spontaneously with their doctors. However, they find relevant that their family doctor brings up the topic with specific questions, because that allows initiating a discussion about some of these sensitive issue. It appears that the awareness of the existing management of geriatric syndromes and functional decline possibilities is rather low. A screening initiative is therefore an opportunity to address these different issues and to inform patients about existing solutions.]]]> fre oai:serval.unil.ch:BIB_7917561D1F2C 2022-05-07T01:20:55Z <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> https://serval.unil.ch/notice/serval:BIB_7917561D1F2C Good and Bad Days: Fluctuations in the Burden of Informal Dementia Caregivers, an Experience Sampling Study. info:doi:10.1097/NNR.0000000000000243 info:eu-repo/semantics/altIdentifier/doi/10.1097/NNR.0000000000000243 info:eu-repo/semantics/altIdentifier/pmid/29095373 Pihet, S. Moses Passini, C. Eicher, M. info:eu-repo/semantics/article article 2017 Nursing research, vol. 66, no. 6, pp. 421-431 info:eu-repo/semantics/altIdentifier/eissn/1538-9847 urn:issn:0029-6562 <![CDATA[Informal dementia caregivers (IDCs) are often confronted with important fluctuations in care-related burden, commonly described as "good and bad days." These fluctuations are overlooked by traditional questionnaires focusing on the average experience. The experience sampling method (ESM) is based on the repeated collection of data in everyday life, thereby allowing the description of day-to-day fluctuations in IDC burden, and the identification of their correlates. ESM studies are still scarce among IDCs, with none focusing on day-to-day fluctuations in burden. This ESM study aimed to examine day-to-day fluctuations in the burden of IDCs and test their associations with six moment-to-moment predictors. Primary IDCs (N = 26, median age = 68 years, 77% women, 73% spouses) volunteered to answer questions about their daily burdens, patients' memories and behavioral problems (MBP), caregivers' MBP-related distress, psychological distress, self-efficacy and positive affects, and relationship quality; volunteers did this every evening for 2 weeks on a touchpad, resulting in 206 measures. Data were analyzed with multilevel linear regression. Day-to-day fluctuations covered about two thirds of the total variance for most study variables. All six predictors had a significant bivariate relation with daily burden, explaining 15%-32% of its fluctuations, with significant differences between caregivers in the strength of these relations. The best multivariate model explained 51% of the day-to-day fluctuations in burden. It included caregiver MBP-related distress, psychological distress, and relationship quality. This innovative study of IDC burden shows that day-to-day fluctuations are an important part of caregivers' real-life experiences and that half of this variability is predicted by currently understudied factors. Inviting caregivers to monitor clinical outcomes daily over 1 or 2 weeks could help tailor interventions to their individual needs and also empower them

Decay rate measurement of the first vibrationally excited state of MgH+^+ in a cryogenic Paul trap

We present a method to measure the decay rate of the first excited vibrational state of simple polar molecular ions being part of a Coulomb crystal in a cryogenic linear Paul trap. Specifically, we have monitored the decay of the $|\nu$=$1,J$=$1 \rangle_X$ towards the $|\nu$=$0,J$=$0 \rangle_X$ level in MgH$^+$ by saturated laser excitation of the $|\nu$=$0,J$=$2 \rangle_X$-$|\nu$=$1,J$=$1 \rangle_X$ transition followed by state selective resonance enhanced two-photon dissociation out of the $|\nu$=$0,J$=$2 \rangle_X$ level. The technique enables the determination of decay rates, and thus absorption strengths, with an accuracy at the few percent level.Comment: 5 pages, 4 figure

Scale Factor Duality: A Quantum Cosmological Approach

We consider the minisuperspace model arising from the lowest order string effective action containing the graviton and the dilaton and study solutions of the resulting Wheeler-Dewitt equation. The scale factor duality symmetry is discussed in the context of our quantum cosmological model.Comment: 10 pages, plain tex, uses panda.tex (appended