The Experts below are selected from a list of 21309 Experts worldwide ranked by ideXlab platform
Kaushik Bhattacharya - One of the best experts on this subject based on the ideXlab platform.
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evolution of scalar and vector cosmological perturbations through a bounce in metric f r gravity in flat flrw spacetime
Journal of Cosmology and Astroparticle Physics, 2019Co-Authors: Pritha Bari, Kaushik BhattacharyaAbstract:In the present work we present the full treatment of scalar and vector cosmological perturbations in a non-singular bouncing universe in the context of metric $f(R)$ cosmology. Scalar metric perturbations in $f(R)$ cosmology were previously calculated in the Jordan Frame, in the present paper we successfully use the Einstein Frame to calculate the scalar metric perturbations where the cosmological bounce takes place in the Jordan Frame. The Einstein Frame Picture presented corrects and completes a previous calculation of scalar perturbations and adds new information. Behavior of fluid velocity potential and the pure vector fluid velocity terms are elaborately calculated for the first time in $f(R)$ cosmology for a bouncing universe in presence of exponential gravity. It is shown that the vector perturbations can remain bounded and almost constant during the non-singular bounce in $f(R)$ gravity unlike general relativistic models where we expect the vector perturbations to be growing during the contracting phase and decaying during the expanding phase. The paper shows that the Einstein Frame can be used for calculation of scalar and vector metric perturbations in a bouncing universe for most of the cases except the case of asymmetric non-singular bounces.
Pritha Bari - One of the best experts on this subject based on the ideXlab platform.
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evolution of scalar and vector cosmological perturbations through a bounce in metric f r gravity in flat flrw spacetime
Journal of Cosmology and Astroparticle Physics, 2019Co-Authors: Pritha Bari, Kaushik BhattacharyaAbstract:In the present work we present the full treatment of scalar and vector cosmological perturbations in a non-singular bouncing universe in the context of metric $f(R)$ cosmology. Scalar metric perturbations in $f(R)$ cosmology were previously calculated in the Jordan Frame, in the present paper we successfully use the Einstein Frame to calculate the scalar metric perturbations where the cosmological bounce takes place in the Jordan Frame. The Einstein Frame Picture presented corrects and completes a previous calculation of scalar perturbations and adds new information. Behavior of fluid velocity potential and the pure vector fluid velocity terms are elaborately calculated for the first time in $f(R)$ cosmology for a bouncing universe in presence of exponential gravity. It is shown that the vector perturbations can remain bounded and almost constant during the non-singular bounce in $f(R)$ gravity unlike general relativistic models where we expect the vector perturbations to be growing during the contracting phase and decaying during the expanding phase. The paper shows that the Einstein Frame can be used for calculation of scalar and vector metric perturbations in a bouncing universe for most of the cases except the case of asymmetric non-singular bounces.
Shoushun Chen - One of the best experts on this subject based on the ideXlab platform.
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a dynamic vision sensor with direct logarithmic output and full Frame Picture on demand
International Symposium on Circuits and Systems, 2017Co-Authors: Jing Huang, Menghan Guo, Shoushun ChenAbstract:This paper presents a Dynamic Vision Sensor with a few interesting features. We directly readout the voltage on the logarithmic photo detector as the intensity information of the fired pixel. The computer is able to command the sensor to produce a full-Frame Picture at whatever time it needs. The sensor was implemented using AMS 0.35 μm 2P4M Opto process with an array of 384 × 320 pixels. Each pixel occupies a footprint of 30 × 30 μm2, with 12% fill factor.
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live demonstration a dynamic vision sensor with direct logarithmic output and full Frame Picture on demand
International Symposium on Circuits and Systems, 2016Co-Authors: Menghan Guo, Ruoxi Ding, Shoushun ChenAbstract:We demonstrate a new Dynamic Vision Sensor (DVS) with 192 × 160 pixels. The sensor has a synchronous interface and can operate at 40 MHz. The pixel event packet consists of three elements: pixel address, time stamp and its intensity. The sensor is able to produce full-array Picture-on-demand. These two unique features will favor subsequent signal processing algorithms such as object tracking and optical flow.
Menghan Guo - One of the best experts on this subject based on the ideXlab platform.
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a dynamic vision sensor with direct logarithmic output and full Frame Picture on demand
International Symposium on Circuits and Systems, 2017Co-Authors: Jing Huang, Menghan Guo, Shoushun ChenAbstract:This paper presents a Dynamic Vision Sensor with a few interesting features. We directly readout the voltage on the logarithmic photo detector as the intensity information of the fired pixel. The computer is able to command the sensor to produce a full-Frame Picture at whatever time it needs. The sensor was implemented using AMS 0.35 μm 2P4M Opto process with an array of 384 × 320 pixels. Each pixel occupies a footprint of 30 × 30 μm2, with 12% fill factor.
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live demonstration a dynamic vision sensor with direct logarithmic output and full Frame Picture on demand
International Symposium on Circuits and Systems, 2016Co-Authors: Menghan Guo, Ruoxi Ding, Shoushun ChenAbstract:We demonstrate a new Dynamic Vision Sensor (DVS) with 192 × 160 pixels. The sensor has a synchronous interface and can operate at 40 MHz. The pixel event packet consists of three elements: pixel address, time stamp and its intensity. The sensor is able to produce full-array Picture-on-demand. These two unique features will favor subsequent signal processing algorithms such as object tracking and optical flow.
Bhattacharya Kaushik - One of the best experts on this subject based on the ideXlab platform.
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Evolution of scalar and vector cosmological perturbations through a bounce in metric $f(R)$ gravity in flat FLRW spacetime
'IOP Publishing', 2019Co-Authors: Bari Pritha, Bhattacharya KaushikAbstract:In the present work we present the full treatment of scalar and vector cosmological perturbations in a non-singular bouncing universe in the context of metric $f(R)$ cosmology. Scalar metric perturbations in $f(R)$ cosmology were previously calculated in the Jordan Frame, in the present paper we successfully use the Einstein Frame to calculate the scalar metric perturbations where the cosmological bounce takes place in the Jordan Frame. The Einstein Frame Picture presented corrects and completes a previous calculation of scalar perturbations and adds new information. Behavior of fluid velocity potential and the pure vector fluid velocity terms are elaborately calculated for the first time in $f(R)$ cosmology for a bouncing universe in presence of exponential gravity. It is shown that the vector perturbations can remain bounded and almost constant during the non-singular bounce in $f(R)$ gravity unlike general relativistic models where we expect the vector perturbations to be growing during the contracting phase and decaying during the expanding phase. The paper shows that the Einstein Frame can be used for calculation of scalar and vector metric perturbations in a bouncing universe for most of the cases except the case of asymmetric non-singular bounces.Comment: The new version is accepted for publication in JCAP. Some material is added to the previous version, new references added and some figures are modified. 23 pages, 14 figure
