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X Wu - One of the best experts on this subject based on the ideXlab platform.
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tests of the einstein equivalence principle using tev blazars
The Astrophysical Journal, 2016Co-Authors: Jieshuang Wang, X WuAbstract:The observed time delays between different energy bands from TeV blazars provide a new, interesting way of testing the Einstein Equivalence Principle (EEP). If the whole time delay is assumed to be dominated by the gravitational field of the Milky Way, the conservative upper limit on the EEP can be estimated. Here, we show that the strict limits on the differences of the parameterized post-Newtonian parameter γ values are for Mrk 421 and for Mrk 501, while expanding the scope of the tested EEP energy range out to the TeV–keV range for the first time. With the small time lag from the 0.2–0.8 TeV and >0.8 TeV light curves of PKS 2155-304, a much more severe constraint on γ differences of ~10−6 can be achieved, although the energy difference is of the order of ~TeV. Furthermore, we can combine these limits on the energy dependence of γ with the Bound on the Absolute γ value from light deflection measurements at the optical (eV) bands, and conclude that this Absolute Bound on γ can be extended from optical to TeV energies.
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cosmic transients test einstein s equivalence principle out to gev energies
The Astrophysical Journal, 2015Co-Authors: X Wu, P MeszarosAbstract:The Einstein Equivalence Principle (EEP) can be probed with astrophysical sources emitting simultaneously different types of neutral particles, or particles with varying energies, by testing their time of flight through the same gravitational field. Here we use the time delays between correlated photons from cosmological transients to constrain the accuracy of the EEP. We take data from two gamma-ray bursts as an example and, as a lower limit to the theoretical time delays between different energies, we use delays arising from only the gravitational field of our own galaxy. We then show that the parameterized post-Newtonian parameter gamma is the same for photons over energy ranges between eV and MeV and between MeV and GeV to a part in 10(-7), which is at least one order of magnitude better than previous limits. Combining this Bound on the wavelength dependence of gamma with the Absolute Bound vertical bar gamma - 1 vertical bar < 0.3% from light-deflection measurements at optical (eV) wavelengths, we thus extend this Absolute Bound on gamma to GeV energies.
P Meszaros - One of the best experts on this subject based on the ideXlab platform.
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cosmic transients test einstein s equivalence principle out to gev energies
The Astrophysical Journal, 2015Co-Authors: X Wu, P MeszarosAbstract:The Einstein Equivalence Principle (EEP) can be probed with astrophysical sources emitting simultaneously different types of neutral particles, or particles with varying energies, by testing their time of flight through the same gravitational field. Here we use the time delays between correlated photons from cosmological transients to constrain the accuracy of the EEP. We take data from two gamma-ray bursts as an example and, as a lower limit to the theoretical time delays between different energies, we use delays arising from only the gravitational field of our own galaxy. We then show that the parameterized post-Newtonian parameter gamma is the same for photons over energy ranges between eV and MeV and between MeV and GeV to a part in 10(-7), which is at least one order of magnitude better than previous limits. Combining this Bound on the wavelength dependence of gamma with the Absolute Bound vertical bar gamma - 1 vertical bar < 0.3% from light-deflection measurements at optical (eV) wavelengths, we thus extend this Absolute Bound on gamma to GeV energies.
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cosmic transients test einstein s equivalence principle out to gev energies
arXiv: High Energy Astrophysical Phenomena, 2015Co-Authors: He Gao, P MeszarosAbstract:The Einstein Equivalence Principle (EEP) can be probed with astrophysical sources emitting simultaneously different types of neutral particles, or particles with varying energies, by testing their time of flight through the same gravitational field. Here we use the time delays between correlated photons from cosmological transients to constrain the accuracy of the EEP. We take data from two gamma-ray bursts as an example, and use, as a lower limit to the theoretical time delays between different energies, delays arising from only the gravitational field of our own galaxy. We then show that the parameterized post-Newtonian parameter $\gamma$ is the same for photons over energy ranges between eV and MeV and between MeV and GeV to a part in $10^{-7}$, which is at least one order of magnitude better than previous limits. Combining this Bound on the wavelength dependence of $\gamma$ with the Absolute Bound $|\gamma-1|<0.3\%$ from light-deflection measurements at optical (eV) wavelengths, we thus extend this Absolute Bound on $\gamma$ to GeV energies.
Michel Verleysen - One of the best experts on this subject based on the ideXlab platform.
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blind source separation based on endpoint estimation with application to the mlsp 2006 data competition
Neurocomputing, 2008Co-Authors: John Aldo Lee, Frederic Vrins, Michel VerleysenAbstract:The problem of blind source separation is usually solved by optimizing a contrast function that measures either the independence of several variables or the non-gaussianity of a single variable. If the problem involves Bounded sources, this knowledge can be exploited and the solution can be found with a customized contrast that relies on a simple endpoint estimator. The minimization of the least Absolute endpoint is closely related to and generalizes the minimization of the range, which has already been studied within the framework of blind source extraction. Using the least Absolute endpoint rather than the range applies to a broader class of admissible sources, which includes sources that are Bounded on a single side and, therefore, have an infinite range. This paper describes some properties of a contrast function based on endpoint estimation, such as the discriminacy. This property guarantees that each local minimum of the least Absolute Bound corresponds to the extraction of one source. An endpoint estimator is proposed, along with a specific deflation algorithm that is able to optimize it. This algorithm relies on a loose orthogonality constraint that reduces the accumulation of errors during the deflation process. This allows the algorithm to solve large-scale and ill-conditioned problems, such as those proposed in the MLSP 2006 data competition. Results show that the proposed algorithm outperforms more generic source separation algorithms like FastICA, as the sources involved in the contest are always Bounded on at least one side.
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a least Absolute Bound approach to ica application to the mlsp 2006 competition
2006 16th IEEE Signal Processing Society Workshop on Machine Learning for Signal Processing, 2006Co-Authors: John Aldo Lee, Frederic Vrins, Michel VerleysenAbstract:This paper describes a least Absolute Bound approach as a way to solve the ICA problems proposed in the 2006 MSLP competition. The least Absolute Bound is an ICA contrast closely related to the support width measure, which has been already studied for the blind extraction of Bounded sources. By comparison, the least Absolute Bound applies to a broader class of sources, including those that are Bounded on a single side only. This precisely corresponds to the sources involved in the competition. Practically, the minimization of the least Absolute Bound relies on a specific deflation algorithm with a loose orthogonality constraint. This allows solving large-scale problems without accumulating errors.
John Aldo Lee - One of the best experts on this subject based on the ideXlab platform.
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blind source separation based on endpoint estimation with application to the mlsp 2006 data competition
Neurocomputing, 2008Co-Authors: John Aldo Lee, Frederic Vrins, Michel VerleysenAbstract:The problem of blind source separation is usually solved by optimizing a contrast function that measures either the independence of several variables or the non-gaussianity of a single variable. If the problem involves Bounded sources, this knowledge can be exploited and the solution can be found with a customized contrast that relies on a simple endpoint estimator. The minimization of the least Absolute endpoint is closely related to and generalizes the minimization of the range, which has already been studied within the framework of blind source extraction. Using the least Absolute endpoint rather than the range applies to a broader class of admissible sources, which includes sources that are Bounded on a single side and, therefore, have an infinite range. This paper describes some properties of a contrast function based on endpoint estimation, such as the discriminacy. This property guarantees that each local minimum of the least Absolute Bound corresponds to the extraction of one source. An endpoint estimator is proposed, along with a specific deflation algorithm that is able to optimize it. This algorithm relies on a loose orthogonality constraint that reduces the accumulation of errors during the deflation process. This allows the algorithm to solve large-scale and ill-conditioned problems, such as those proposed in the MLSP 2006 data competition. Results show that the proposed algorithm outperforms more generic source separation algorithms like FastICA, as the sources involved in the contest are always Bounded on at least one side.
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a least Absolute Bound approach to ica application to the mlsp 2006 competition
2006 16th IEEE Signal Processing Society Workshop on Machine Learning for Signal Processing, 2006Co-Authors: John Aldo Lee, Frederic Vrins, Michel VerleysenAbstract:This paper describes a least Absolute Bound approach as a way to solve the ICA problems proposed in the 2006 MSLP competition. The least Absolute Bound is an ICA contrast closely related to the support width measure, which has been already studied for the blind extraction of Bounded sources. By comparison, the least Absolute Bound applies to a broader class of sources, including those that are Bounded on a single side only. This precisely corresponds to the sources involved in the competition. Practically, the minimization of the least Absolute Bound relies on a specific deflation algorithm with a loose orthogonality constraint. This allows solving large-scale problems without accumulating errors.
Jieshuang Wang - One of the best experts on this subject based on the ideXlab platform.
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tests of the einstein equivalence principle using tev blazars
The Astrophysical Journal, 2016Co-Authors: Jieshuang Wang, X WuAbstract:The observed time delays between different energy bands from TeV blazars provide a new, interesting way of testing the Einstein Equivalence Principle (EEP). If the whole time delay is assumed to be dominated by the gravitational field of the Milky Way, the conservative upper limit on the EEP can be estimated. Here, we show that the strict limits on the differences of the parameterized post-Newtonian parameter γ values are for Mrk 421 and for Mrk 501, while expanding the scope of the tested EEP energy range out to the TeV–keV range for the first time. With the small time lag from the 0.2–0.8 TeV and >0.8 TeV light curves of PKS 2155-304, a much more severe constraint on γ differences of ~10−6 can be achieved, although the energy difference is of the order of ~TeV. Furthermore, we can combine these limits on the energy dependence of γ with the Bound on the Absolute γ value from light deflection measurements at the optical (eV) bands, and conclude that this Absolute Bound on γ can be extended from optical to TeV energies.
