The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Hilbert J. Kappen - One of the best experts on this subject based on the ideXlab platform.
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Path Integral control and state dependent feedback
Physical Review E, 2015Co-Authors: Sep Thijssen, Hilbert J. KappenAbstract:: In this paper we address the problem of computing state-dependent feedback controls for Path Integral control problems. To this end we generalize the Path Integral control formula and utilize this to construct parametrized state-dependent feedback controllers. In addition, we show a relation between control and importance sampling: Better control, in terms of control cost, yields more efficient importance sampling, in terms of effective sample size. The optimal control provides a zero-variance estimate.
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policy search for Path Integral control
European conference on Machine Learning, 2014Co-Authors: Vicenc Gomez, Hilbert J. Kappen, Jan Peters, Gerhard NeumannAbstract:Path Integral (PI) control defines a general class of control problems for which the optimal control computation is equivalent to an inference problem that can be solved by evaluation of a Path Integral over state trajectories. However, this potential is mostly unused in real-world problems because of two main limitations: first, current approaches can typically only be applied to learn open-loop controllers and second, current sampling procedures are inefficient and not scalable to high dimensional systems. We introduce the efficient Path Integral Relative-Entropy Policy Search (PI-REPS) algorithm for learning feedback policies with PI control. Our algorithm is inspired by information theoretic policy updates that are often used in policy search. We use these updates to approximate the state trajectory distribution that is known to be optimal from the PI control theory. Our approach allows for a principled treatment of different sampling distributions and can be used to estimate many types of parametric or non-parametric feedback controllers. We show that PI-REPS significantly outperforms current methods and is able to solve tasks that are out of reach for current methods.
Muxin Han - One of the best experts on this subject based on the ideXlab platform.
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a Path Integral for the master constraint of loop quantum gravity
Classical and Quantum Gravity, 2010Co-Authors: Muxin HanAbstract:In the present paper, we start from the canonical theory of loop quantum gravity and the master constraint program. The physical inner product is expressed by using the group averaging technique for a single self-adjoint master constraint operator. By the standard technique of skeletonization and the coherent state Path Integral, we derive a Path-Integral formula from the group averaging for the master constraint operator. Our derivation in this paper suggests there exists a direct link connecting the canonical loop quantum gravity with a Path-Integral quantization or a spin-foam model of general relativity.
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a Path Integral for the master constraint of loop quantum gravity
arXiv: General Relativity and Quantum Cosmology, 2009Co-Authors: Muxin HanAbstract:In the present paper, we start from the canonical theory of loop quantum gravity and the master constraint programme. The physical inner product is expressed by using the group averaging technique for a single self-adjoint master constraint operator. By the standard technique of skeletonization and the coherent state Path-Integral, we derive a Path-Integral formula from the group averaging for the master constraint operator. Our derivation in the present paper suggests there exists a direct link connecting the canonical Loop quantum gravity with a Path-Integral quantization or a spin-foam model of General Relativity.
K L Sebastian - One of the best experts on this subject based on the ideXlab platform.
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Path Integral representation for fractional brownian motion
Journal of Physics A, 1995Co-Authors: K L SebastianAbstract:Fractional Brownian motion (FBM) is a generalization of the usual Brownian motion. A Path Integral representation that has recently been suggested for it is shown to be not for the FBM but for a different generalization of the Brownian motion. A new Path Integral representation is given and its measure has fractional derivatives of the Path in it. The measure shows that the process is Gaussian but is, in general, non-Markovian, even though Brownian motion itself is Markovian. It is shown how the propagator for the motion of free FBM may be evaluated. This is somewhat more complex than for the usual Path Integrals, due to the occurrence of fractional derivatives. We also find the propagator in the presence of a linear absorption (potential), and for FBM on a ring.
Enrique Muñoz - One of the best experts on this subject based on the ideXlab platform.
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The stepwise Path Integral of the relativistic point particle
The European Physical Journal C, 2018Co-Authors: Benjamin Koch, Enrique MuñozAbstract:In this paper we present a stepwise construction of the Path Integral over relativistic orbits in Euclidean spacetime. It is shown that the apparent problems of this Path Integral, like the breakdown of the naive Chapman–Kolmogorov relation, can be solved by a careful analysis of the overcounting associated with local and global symmetries. Based on this, the direct calculation of the quantum propagator of the relativistic point particle in the Path Integral formulation results from a simple and purely geometric construction.
Yuki Yokokura - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamical Path Integral and emergent symmetry.
Physical Review E, 2019Co-Authors: Shin-ichi Sasa, Sho Sugiura, Yuki YokokuraAbstract:We investigate a thermally isolated quantum many-body system with an external control represented by a step protocol of a parameter. The propagator at each step of the parameter change is described by thermodynamic quantities under some assumptions. For the time evolution of such systems, we formulate a Path Integral over the trajectories in the thermodynamic state space. In particular, for quasistatic operations, we derive an effective action of the thermodynamic entropy and its canonically conjugate variable. Then, the symmetry for the uniform translation of the conjugate variable emerges in the Path Integral. This leads to the entropy as a Noether invariant in quantum mechanics.
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Thermal pure state Path Integral and emergent symmetry
arXiv: Statistical Mechanics, 2016Co-Authors: Shin-ichi Sasa, Yuki Yokokura, Sho SugiuraAbstract:We investigate a thermally isolated quantum many-body system with an external control represented by a time-dependent parameter. We formulate a Path Integral in terms of thermal pure states and derive an effective action for trajectories in a thermodynamic state space, where the entropy appears with its conjugate variable. In particular, for quasi-static operations, the symmetry for the uniform translation of the conjugate variable emerges in the Path Integral. This leads to the entropy as a Noether invariant.
