The Experts below are selected from a list of 35322 Experts worldwide ranked by ideXlab platform
Chris R Brewin - One of the best experts on this subject based on the ideXlab platform.
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contextualisation in the revised Dual Representation theory of ptsd a response to pearson and colleagues
2014Co-Authors: Chris R Brewin, Neil BurgessAbstract:Three recent studies (Pearson, 2012; Pearson, Ross, & Webster, 2012) purported to test the revised Dual Representation theory of posttraumatic stress disorder (Brewin, Gregory, Lipton, & Burgess, 2010) by manipulating the amount of additional information accompanying traumatic stimulus materials and assessing the effect on subsequent intrusive memories. Here we point out that these studies involve a misunderstanding of the meaning of “contextual” within the theory, such that the manipulation would be unlikely to have had the intended effect and the results are ambiguous with respect to the theory. Past and future experimental tests of the theory are discussed.
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acute effects of alcohol on intrusive memory development and viewpoint dependence in spatial memory support a Dual Representation model
2010Co-Authors: James A Bisby, Chris R Brewin, Neil Burgess, John A King, Valerie H CurranAbstract:Background A Dual Representation model of intrusive memory proposes that personally experienced events give rise to two types of Representation: an image-based, egocentric Representation based on sensory-perceptual features; and a more abstract, allocentric Representation that incorporates spatiotemporal context. The model proposes that intrusions reflect involuntary reactivation of egocentric Representations in the absence of a corresponding allocentric Representation. We tested the model by investigating the effect of alcohol on intrusive memories and, concurrently, on egocentric and allocentric spatial memory. Methods With a double-blind independent group design participants were administered alcohol (.4 or .8 g/kg) or placebo. A virtual environment was used to present objects and test recognition memory from the same viewpoint as presentation (tapping egocentric memory) or a shifted viewpoint (tapping allocentric memory). Participants were also exposed to a trauma video and required to detail intrusive memories for 7 days, after which explicit memory was assessed. Results There was a selective impairment of shifted-view recognition after the low dose of alcohol, whereas the high dose induced a global impairment in same-view and shifted-view conditions. Alcohol showed a dose-dependent inverted ”U”-shaped effect on intrusions, with only the low dose increasing the number of intrusions, replicating previous work. When same-view recognition was intact, decrements in shifted-view recognition were associated with increases in intrusions. Conclusions The differential effect of alcohol on intrusive memories and on same/shifted-view recognition support a Dual Representation model in which intrusions might reflect an imbalance between two types of memory Representation. These findings highlight important clinical implications, given alcohol's involvement in real-life trauma.
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a cognitive neuroscience account of posttraumatic stress disorder and its treatment
2001Co-Authors: Chris R BrewinAbstract:Recent research in the areas of animal conditioning, the neural systems underlying emotion and memory, and the effect of fear on these systems is reviewed. This evidence points to an important distinction between hippocampally-dependent and non-hippocampally-dependent forms of memory that are differentially affected by extreme stress. The cognitive science perspective is related to a recent model of posttraumatic stress disorder, Dual Representation theory, that also posits separate memory systems underlying vivid reexperiencing versus ordinary autobiographical memories of trauma. This view is compared with other accounts in the literature of traumatic memory processes in PTSD, and the contrasting implications for therapy are discussed.
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a Dual Representation theory of posttraumatic stress disorder
1996Co-Authors: Chris R Brewin, Tim Dalgleish, Stephen JosephAbstract:A cognitive theory of post traumatic stress disorder (PTSD) is proposed that assumes traumas experienced after early childhood give rise to 2 sorts of memory, 1 verbally accessible and 1 automatically accessible through appropriate situational cues. These different types of memory are used to explain the complex phenomenology of PTSD, including the experiences of reliving the traumatic event and of emotionally processing the trauma. The theory considers 3 possible outcomes of the emotional processing of trauma, successful completion, chronic processing, and premature inhibition of processing. We discuss the implications of the theory for research design, clinical practice, and resolving contradictions in the empirical data.
Christof Gattringer - One of the best experts on this subject based on the ideXlab platform.
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Dual Representation of lattice qcd with worldlines and worldsheets of abelian color fluxes
2018Co-Authors: Carlotta Marchis, Christof GattringerAbstract:We present a new Dual Representation for lattice QCD in terms of wordlines and worldsheets. The exact reformulation is carried out using the recently developed abelian color flux method where the action is decomposed into commuting minimal terms that connect different colors on neighboring sites. Expanding the Boltzmann factors for these commuting terms allows one to reorganize the gauge field contributions according to links such that the gauge fields can be integrated out in closed form. The emerging constraints give the Dual variables the structure of worldlines for the fermions and worldsheets for the gauge degrees of freedom. The partition sum has the form of a strong coupling expansion and with the abelian color flux approach discussed here all coefficients of the expansion are known in closed form. We present the Dual form for three cases: pure SU(3) lattice gauge theory, strong coupling QCD and full QCD, and discuss in detail the constraints for the color fluxes and their physical interpretation.
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solving the sign problems of the massless lattice schwinger model with a Dual formulation
2015Co-Authors: Christof Gattringer, Thomas Kloiber, Vasily SazonovAbstract:Abstract We derive an exact Representation of the massless Schwinger model on the lattice in terms of Dual variables which are configurations of loops, dimers and plaquette occupation numbers. When expressed with the Dual variables the partition sum has only real and positive terms also when a chemical potential or a topological term are added – situations where the conventional Representation has a complex action problem. The Dual Representation allows for Monte Carlo simulations without restrictions on the values of the chemical potential or the vacuum angle.
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scalar qed _2 with a topological term a lattice study in a Dual Representation
2014Co-Authors: Thomas Kloiber, Christof GattringerAbstract:We present a Dual Representation for the partition function of 2-dimensional scalar quantum electrodynamics with a topological term (q -term). In the Dual Representation the complex action problem at non-zero q is absent, which is an obstacle for Monte Carlo simulations in the conventional form of the model. We discuss the technical aspects of the Dual Representation and show that a Dual Monte Carlo simulation can be implemented. As a first application we demonstrate how the 2p-periodicity of physical observables is recovered in a suitable continuum limit.
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Dual lattice simulation of the abelian gauge higgs model at finite density an exploratory proof of concept study
2013Co-Authors: Ydalia Delgado Mercado, Christof Gattringer, Albrecht SchmidtAbstract:The U(1) gauge-Higgs model with two flavors of opposite charge and a chemical potential is mapped exactly to a Dual Representation where matter fields correspond to loops of flux and the gauge fields are represented by surfaces. The complex action problem of the conventional formulation at finite chemical potential μ is overcome in the Dual Representation, and the partition sum has only real and nonzero contributions. We simulate the model in the Dual Representation using a generalized worm algorithm, explore the phase diagram, and study condensation phenomena at finite μ.
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monte carlo simulation of abelian gauge higgs lattice models using Dual Representation
2012Co-Authors: Albrecht Schmidt, Ydalia Delgado Mercado, Christof GattringerAbstract:We study abelian gauge-Higgs models on the lattice and consider gauge groups Z(3) and U(1). For both cases the partition sums are mapped exactly to a Dual Representation where the degrees of freedom are surfaces for the gauge fields and loops of flux that may serve as boundaries for the surfaces represent the matter fields. Also at finite chemical potential the Dual partition sums have only real and positive contributions and the complex action problem of the conventional Representation is overcome in the Dual approach. We apply a local Metropolis update for the Dual degrees of freedom, as well as a generalization of the worm algorithm to bounded surfaces. Results that illustrate condensation phenomena as a function of chemical potential are discussed.
Prashant Kumar - One of the best experts on this subject based on the ideXlab platform.
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numerical study of a Dual Representation of the integer quantum hall transition
2021Co-Authors: Kevin S Huang, Srinivas Raghu, Prashant KumarAbstract:We study the critical properties of the noninteracting integer quantum Hall to insulator transition (IQHIT) in a "Dual" composite-fermion (CF) Representation. A key advantage of the CF Representation over electron coordinates is that at criticality CF states are delocalized at all energies. The CF approach thus enables us to study the transition from a new vantage point. Using a lattice Representation of CF mean-field theory, we compute the critical and multifractal exponents of the IQHIT. We obtain ν=2.56±0.02 and η=0.51±0.01, both of which are consistent with the predictions of the Chalker-Coddington network model formulated in the electron Representation.
Liangpei Zhang - One of the best experts on this subject based on the ideXlab platform.
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Learning Attraction Field Representation for Robust Line Segment Detection
2019Co-Authors: Nan Xue, Song Bai, Fudong Wang, Gui-song Xia, Liangpei ZhangAbstract:This paper presents a region-partition based attraction field Dual Representation for line segment maps, and thus poses the problem of line segment detection (LSD) as the region coloring problem. The latter is then addressed by learning deep convolutional neural networks (ConvNets) for accuracy, robustness and efficiency. For a 2D line segment map, our Dual Representation consists of three components: (i) A region-partition map in which every pixel is assigned to one and only one line segment; (ii) An attraction field map in which every pixel in a partition region is encoded by its 2D projection vector w.r.t. the associated line segment; and (iii) A squeeze module which squashes the attraction field to a line segment map that almost perfectly recovers the input one. By leveraging the Duality, we learn ConvNets to compute the attraction field maps for raw in-put images, followed by the squeeze module for LSD, in an end-to-end manner. Our method rigorously addresses several challenges in LSD such as local ambiguity and class imbalance. Our method also harnesses the best practices developed in ConvNets based semantic segmentation methods such as the encoder-decoder architecture and the a-trous convolution. In experiments, our method is tested on the WireFrame dataset and the YorkUrban dataset with state-of-the-art performance obtained. Especially, we advance the performance by 4.5 percents on the WireFramedataset. Our method is also fast with 6.6~10.4 FPS, outperforming most of existing line segment detectors.
Wolfgang Unger - One of the best experts on this subject based on the ideXlab platform.
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new Dual Representation for staggered lattice qcd
2020Co-Authors: Giuseppe Gagliardi, Wolfgang UngerAbstract:We propose a new strategy to evaluate the partition function of lattice QCD with Wilson gauge action coupled to staggered fermions, based on a strong coupling expansion in the inverse bare gauge coupling $\beta= 2N/g^{2}$. Our method makes use of the recently developed formalism to evaluate the ${\rm SU}(N)$ $1-$link integrals and consists in an exact rewriting of the partition function in terms of a set of additional Dual degrees of freedom which we call "Decoupling Operator Indices" (DOI). The method is not limited to any particular number of dimensions or gauge group ${\rm U}(N)$, ${\rm SU}(N)$. In terms of the DOI the system takes the form of a Tensor Network which can be simulated using Worm-like algorithms. Higher order $\beta$-corrections to strong coupling lattice QCD can be, in principle, systematically evaluated, helping to answer the question whether the finite density sign problem remains mild when plaquette contributions are included. Issues related to the complexity of the description and strategies for the stochastic evaluation of the partition function are discussed.
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new Dual Representation for staggered lattice qcd
2020Co-Authors: Giuseppe Gagliardi, Wolfgang UngerAbstract:We propose a new strategy to evaluate the partition function of lattice QCD with Wilson gauge action coupled to staggered fermions, based on a strong coupling expansion in the inverse bare gauge coupling $\ensuremath{\beta}=2N/{g}^{2}$. Our method makes use of the recently developed formalism to evaluate the $\mathrm{SU}(N)$ 1-link integrals and consists in an exact rewriting of the partition function in terms of a set of additional Dual degrees of freedom which we call ``decoupling operator indices'' (DOI). The method is not limited to any particular number of dimensions or gauge group $\mathrm{U}(N)$, $\mathrm{SU}(N)$. In terms of the DOI, the system takes the form of a tensor network which can be simulated using wormlike algorithms. Higher order $\ensuremath{\beta}$-corrections to strong coupling lattice QCD can be, in principle, systematically evaluated, helping to answer the question whether the finite density sign problem remains mild when plaquette contributions are included. Issues related to the complexity of the description and strategies for the stochastic evaluation of the partition function are discussed.
