The Experts below are selected from a list of 13560 Experts worldwide ranked by ideXlab platform
Salvador Miretartes - One of the best experts on this subject based on the ideXlab platform.
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quantum threshold reflection is not a consequence of a region of the long range attractive potential with rapidly varying de broglie wavelength
Physical Review A, 2018Co-Authors: Jakob Petersen, Eli Pollak, Salvador MiretartesAbstract:Quantum threshold reflection is a well known quantum phenomenon which prescribes that at threshold, except for special circumstances, a quantum Particle scattering from any potential, even if attractive at long range, will be reflected with unit probability. In the past, this property has been associated with the so-called badlands region of the potential, where the semiclassical description of the scattering fails due to a rapid spatial variation of the deBroglie wavelength. This badlands region occurs far from the strong interaction region of the potential and has therefore been used to "explain" the quantum reflection phenomenon. In this paper, we show that the badlands region of the interaction potential is immaterial. The extremely long wavelength of the Scattered Particle at threshold is much longer than the spatial extension of the badlands region which therefore does not affect the scattering. For this purpose, we review the general proof for the existence of quantum threshold reflection to stress that it is only a consequence of continuity and boundary conditions. The nonlocal character of the scattering implies that the whole interaction potential is involved in the phenomenon. We then provide a detailed numerical study of the threshold scattering of a Particle by a Morse potential especially in the time domain. We compare exact quantum computations with incoherent results obtained from a classical Wigner approximation. This study shows that close to threshold the time dependent amplitude of the Scattered Particle is negligible in the badlands region and that the mean flight time of the Particle is not shortened due to a local reflection from the badlands region. This study should serve to definitely rule out the badlands region as a qualitative guide to the properties of quantum threshold reflection.
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quantum threshold reflection is not a consequence of a region of the long range attractive potential with rapidly varying de broglie wavelength
Physical Review A, 2018Co-Authors: Jakob Petersen, Eli Pollak, Salvador MiretartesAbstract:Quantum threshold reflection is a well-known quantum phenomenon which prescribes that at threshold, except for special circumstances, a quantum Particle scattering from any potential, even if attractive at long range, will be reflected with unit probability. In the past, this property had been associated with the so-called badlands region of the potential, where the semiclassical description of the scattering fails due to a rapid spatial variation of the de Broglie wavelength. This badlands region occurs far from the strong interaction region of the potential and has therefore been used to ``explain'' the quantum reflection phenomenon. In this paper we show that the badlands region of the interaction potential is immaterial. The extremely long wavelength of the Scattered Particle at threshold is much longer than the spatial extension of the badlands region, which therefore does not affect the scattering. For this purpose, we review and generalize the proof for the existence of quantum threshold reflection to stress that it is only a consequence of continuity and boundary conditions. The nonlocal character of the scattering implies that the whole interaction potential is involved in the phenomenon. We then provide a detailed numerical study of the threshold scattering of a Particle by a Morse potential and an Eckart potential, especially in the time domain. We compare exact quantum computations with incoherent results obtained from a classical Wigner approximation. This study shows that close to threshold the time-dependent amplitude of the Scattered Particle is negligible in the badlands region and is the same whether the potential has a reflecting wall as in the Morse potential or a steplike structure as in the Eckart smooth step potential. The mean flight time of the Particle is not shortened due to a local reflection from the badlands region or due to the lower density of the wave function at short distances. This study should serve to definitely rule out the badlands region as a qualitative guide to the properties of quantum threshold reflection.
Jakob Petersen - One of the best experts on this subject based on the ideXlab platform.
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quantum threshold reflection is not a consequence of a region of the long range attractive potential with rapidly varying de broglie wavelength
Physical Review A, 2018Co-Authors: Jakob Petersen, Eli Pollak, Salvador MiretartesAbstract:Quantum threshold reflection is a well known quantum phenomenon which prescribes that at threshold, except for special circumstances, a quantum Particle scattering from any potential, even if attractive at long range, will be reflected with unit probability. In the past, this property has been associated with the so-called badlands region of the potential, where the semiclassical description of the scattering fails due to a rapid spatial variation of the deBroglie wavelength. This badlands region occurs far from the strong interaction region of the potential and has therefore been used to "explain" the quantum reflection phenomenon. In this paper, we show that the badlands region of the interaction potential is immaterial. The extremely long wavelength of the Scattered Particle at threshold is much longer than the spatial extension of the badlands region which therefore does not affect the scattering. For this purpose, we review the general proof for the existence of quantum threshold reflection to stress that it is only a consequence of continuity and boundary conditions. The nonlocal character of the scattering implies that the whole interaction potential is involved in the phenomenon. We then provide a detailed numerical study of the threshold scattering of a Particle by a Morse potential especially in the time domain. We compare exact quantum computations with incoherent results obtained from a classical Wigner approximation. This study shows that close to threshold the time dependent amplitude of the Scattered Particle is negligible in the badlands region and that the mean flight time of the Particle is not shortened due to a local reflection from the badlands region. This study should serve to definitely rule out the badlands region as a qualitative guide to the properties of quantum threshold reflection.
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quantum threshold reflection is not a consequence of a region of the long range attractive potential with rapidly varying de broglie wavelength
Physical Review A, 2018Co-Authors: Jakob Petersen, Eli Pollak, Salvador MiretartesAbstract:Quantum threshold reflection is a well-known quantum phenomenon which prescribes that at threshold, except for special circumstances, a quantum Particle scattering from any potential, even if attractive at long range, will be reflected with unit probability. In the past, this property had been associated with the so-called badlands region of the potential, where the semiclassical description of the scattering fails due to a rapid spatial variation of the de Broglie wavelength. This badlands region occurs far from the strong interaction region of the potential and has therefore been used to ``explain'' the quantum reflection phenomenon. In this paper we show that the badlands region of the interaction potential is immaterial. The extremely long wavelength of the Scattered Particle at threshold is much longer than the spatial extension of the badlands region, which therefore does not affect the scattering. For this purpose, we review and generalize the proof for the existence of quantum threshold reflection to stress that it is only a consequence of continuity and boundary conditions. The nonlocal character of the scattering implies that the whole interaction potential is involved in the phenomenon. We then provide a detailed numerical study of the threshold scattering of a Particle by a Morse potential and an Eckart potential, especially in the time domain. We compare exact quantum computations with incoherent results obtained from a classical Wigner approximation. This study shows that close to threshold the time-dependent amplitude of the Scattered Particle is negligible in the badlands region and is the same whether the potential has a reflecting wall as in the Morse potential or a steplike structure as in the Eckart smooth step potential. The mean flight time of the Particle is not shortened due to a local reflection from the badlands region or due to the lower density of the wave function at short distances. This study should serve to definitely rule out the badlands region as a qualitative guide to the properties of quantum threshold reflection.
Gabriele Travaglini - One of the best experts on this subject based on the ideXlab platform.
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eikonal phase matrix deflection angle and time delay in effective field theories of gravity
Physical Review D, 2020Co-Authors: Manuel Accettulli Huber, Andreas Brandhuber, Stefano De Angelis, Gabriele TravagliniAbstract:The eikonal approximation is an ideal tool to extract classical observables in gauge theory and gravity directly from scattering amplitudes. Here we consider effective theories of gravity where in addition to the Einstein-Hilbert term we include nonminimal couplings of the type ${R}^{3}$, ${R}^{4}$ and FFR. In particular, we study the scattering of gravitons and photons of frequency $\ensuremath{\omega}$ off heavy scalars of mass $m$ in the limit $m\ensuremath{\gg}\ensuremath{\omega}\ensuremath{\gg}|\stackrel{\ensuremath{\rightarrow}}{q}|$, where $\stackrel{\ensuremath{\rightarrow}}{q}$ is the momentum transfer. The presence of nonminimal couplings induces helicity-flip processes which survive the eikonal limit, thereby promoting the eikonal phase to an eikonal phase matrix. We obtain the latter from the relevant two-to-two helicity amplitudes that we compute up to one-loop order, and confirm that the leading-order terms in $\ensuremath{\omega}$ exponentiate \`a la Amati, Ciafaloni and Veneziano. From the eigenvalues of the eikonal phase matrix we then extract two physical observables, to 2PM order: the classical deflection angle and Shapiro time delay/advance. Whenever the classical expectation of helicity conservation of the massless Scattered Particle is violated, i.e., the eigenvalues of the eikonal matrix are nondegenerate, causality violation due to time advance is a generic possibility for small impact parameter. We show that for graviton scattering in the ${R}^{4}$ and FFR theories, time advance is circumvented if the couplings of these interactions satisfy certain positivity conditions, while it is unavoidable for graviton scattering in the ${R}^{3}$ theory and photon scattering in the FFR theory. The scattering processes we consider mimic the deflection of photons and gravitons off spinless heavy objects such as black holes.
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eikonal phase matrix deflection angle and time delay in effective field theories of gravity
Physical Review D, 2020Co-Authors: Manuel Accettulli Huber, Andreas Brandhuber, Stefano De Angelis, Gabriele TravagliniAbstract:The eikonal approximation is an ideal tool to extract classical observables in gauge theory and gravity directly from scattering amplitudes. Here we consider effective theories of gravity where in addition to the Einstein-Hilbert term we include non-minimal couplings of the type $R^3$, $R^4$ and $FFR$. In particular, we study the scattering of gravitons and photons of frequency $\omega$ off heavy scalars of mass $m$ in the limit $m\gg \omega \gg |\vec{q}\,|$, where $\vec{q}$ is the momentum transfer. The presence of non-minimal couplings induces helicity-flip processes which survive the eikonal limit, thereby promoting the eikonal phase to an eikonal phase matrix. We obtain the latter from the relevant two-to-two helicity amplitudes that we compute up to one-loop order, and confirm that the leading-order terms in $\omega$ exponentiate a la Amati, Ciafaloni and Veneziano. From the eigenvalues of the eikonal phase matrix we then extract two physical observables, to 2PM order: the classical deflection angle and Shapiro time delay/advance. Whenever the classical expectation of helicity conservation of the massless Scattered Particle is violated, i.e. the eigenvalues of the eikonal matrix are non-degenerate, causality violation due to time advance is a generic possibility for small impact parameter. We show that for graviton scattering in the $R^4$ and $FFR$ theories, time advance is circumvented if the couplings of these interactions satisfy certain positivity conditions, while it is unavoidable for graviton scattering in the $R^3$ theory and photon scattering in the $FFR$ theory. The scattering processes we consider mimic the deflection of photons and gravitons off spinless heavy objects such as black~holes.
Eli Pollak - One of the best experts on this subject based on the ideXlab platform.
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quantum threshold reflection is not a consequence of a region of the long range attractive potential with rapidly varying de broglie wavelength
Physical Review A, 2018Co-Authors: Jakob Petersen, Eli Pollak, Salvador MiretartesAbstract:Quantum threshold reflection is a well known quantum phenomenon which prescribes that at threshold, except for special circumstances, a quantum Particle scattering from any potential, even if attractive at long range, will be reflected with unit probability. In the past, this property has been associated with the so-called badlands region of the potential, where the semiclassical description of the scattering fails due to a rapid spatial variation of the deBroglie wavelength. This badlands region occurs far from the strong interaction region of the potential and has therefore been used to "explain" the quantum reflection phenomenon. In this paper, we show that the badlands region of the interaction potential is immaterial. The extremely long wavelength of the Scattered Particle at threshold is much longer than the spatial extension of the badlands region which therefore does not affect the scattering. For this purpose, we review the general proof for the existence of quantum threshold reflection to stress that it is only a consequence of continuity and boundary conditions. The nonlocal character of the scattering implies that the whole interaction potential is involved in the phenomenon. We then provide a detailed numerical study of the threshold scattering of a Particle by a Morse potential especially in the time domain. We compare exact quantum computations with incoherent results obtained from a classical Wigner approximation. This study shows that close to threshold the time dependent amplitude of the Scattered Particle is negligible in the badlands region and that the mean flight time of the Particle is not shortened due to a local reflection from the badlands region. This study should serve to definitely rule out the badlands region as a qualitative guide to the properties of quantum threshold reflection.
-
quantum threshold reflection is not a consequence of a region of the long range attractive potential with rapidly varying de broglie wavelength
Physical Review A, 2018Co-Authors: Jakob Petersen, Eli Pollak, Salvador MiretartesAbstract:Quantum threshold reflection is a well-known quantum phenomenon which prescribes that at threshold, except for special circumstances, a quantum Particle scattering from any potential, even if attractive at long range, will be reflected with unit probability. In the past, this property had been associated with the so-called badlands region of the potential, where the semiclassical description of the scattering fails due to a rapid spatial variation of the de Broglie wavelength. This badlands region occurs far from the strong interaction region of the potential and has therefore been used to ``explain'' the quantum reflection phenomenon. In this paper we show that the badlands region of the interaction potential is immaterial. The extremely long wavelength of the Scattered Particle at threshold is much longer than the spatial extension of the badlands region, which therefore does not affect the scattering. For this purpose, we review and generalize the proof for the existence of quantum threshold reflection to stress that it is only a consequence of continuity and boundary conditions. The nonlocal character of the scattering implies that the whole interaction potential is involved in the phenomenon. We then provide a detailed numerical study of the threshold scattering of a Particle by a Morse potential and an Eckart potential, especially in the time domain. We compare exact quantum computations with incoherent results obtained from a classical Wigner approximation. This study shows that close to threshold the time-dependent amplitude of the Scattered Particle is negligible in the badlands region and is the same whether the potential has a reflecting wall as in the Morse potential or a steplike structure as in the Eckart smooth step potential. The mean flight time of the Particle is not shortened due to a local reflection from the badlands region or due to the lower density of the wave function at short distances. This study should serve to definitely rule out the badlands region as a qualitative guide to the properties of quantum threshold reflection.
Manuel Accettulli Huber - One of the best experts on this subject based on the ideXlab platform.
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eikonal phase matrix deflection angle and time delay in effective field theories of gravity
Physical Review D, 2020Co-Authors: Manuel Accettulli Huber, Andreas Brandhuber, Stefano De Angelis, Gabriele TravagliniAbstract:The eikonal approximation is an ideal tool to extract classical observables in gauge theory and gravity directly from scattering amplitudes. Here we consider effective theories of gravity where in addition to the Einstein-Hilbert term we include nonminimal couplings of the type ${R}^{3}$, ${R}^{4}$ and FFR. In particular, we study the scattering of gravitons and photons of frequency $\ensuremath{\omega}$ off heavy scalars of mass $m$ in the limit $m\ensuremath{\gg}\ensuremath{\omega}\ensuremath{\gg}|\stackrel{\ensuremath{\rightarrow}}{q}|$, where $\stackrel{\ensuremath{\rightarrow}}{q}$ is the momentum transfer. The presence of nonminimal couplings induces helicity-flip processes which survive the eikonal limit, thereby promoting the eikonal phase to an eikonal phase matrix. We obtain the latter from the relevant two-to-two helicity amplitudes that we compute up to one-loop order, and confirm that the leading-order terms in $\ensuremath{\omega}$ exponentiate \`a la Amati, Ciafaloni and Veneziano. From the eigenvalues of the eikonal phase matrix we then extract two physical observables, to 2PM order: the classical deflection angle and Shapiro time delay/advance. Whenever the classical expectation of helicity conservation of the massless Scattered Particle is violated, i.e., the eigenvalues of the eikonal matrix are nondegenerate, causality violation due to time advance is a generic possibility for small impact parameter. We show that for graviton scattering in the ${R}^{4}$ and FFR theories, time advance is circumvented if the couplings of these interactions satisfy certain positivity conditions, while it is unavoidable for graviton scattering in the ${R}^{3}$ theory and photon scattering in the FFR theory. The scattering processes we consider mimic the deflection of photons and gravitons off spinless heavy objects such as black holes.
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eikonal phase matrix deflection angle and time delay in effective field theories of gravity
Physical Review D, 2020Co-Authors: Manuel Accettulli Huber, Andreas Brandhuber, Stefano De Angelis, Gabriele TravagliniAbstract:The eikonal approximation is an ideal tool to extract classical observables in gauge theory and gravity directly from scattering amplitudes. Here we consider effective theories of gravity where in addition to the Einstein-Hilbert term we include non-minimal couplings of the type $R^3$, $R^4$ and $FFR$. In particular, we study the scattering of gravitons and photons of frequency $\omega$ off heavy scalars of mass $m$ in the limit $m\gg \omega \gg |\vec{q}\,|$, where $\vec{q}$ is the momentum transfer. The presence of non-minimal couplings induces helicity-flip processes which survive the eikonal limit, thereby promoting the eikonal phase to an eikonal phase matrix. We obtain the latter from the relevant two-to-two helicity amplitudes that we compute up to one-loop order, and confirm that the leading-order terms in $\omega$ exponentiate a la Amati, Ciafaloni and Veneziano. From the eigenvalues of the eikonal phase matrix we then extract two physical observables, to 2PM order: the classical deflection angle and Shapiro time delay/advance. Whenever the classical expectation of helicity conservation of the massless Scattered Particle is violated, i.e. the eigenvalues of the eikonal matrix are non-degenerate, causality violation due to time advance is a generic possibility for small impact parameter. We show that for graviton scattering in the $R^4$ and $FFR$ theories, time advance is circumvented if the couplings of these interactions satisfy certain positivity conditions, while it is unavoidable for graviton scattering in the $R^3$ theory and photon scattering in the $FFR$ theory. The scattering processes we consider mimic the deflection of photons and gravitons off spinless heavy objects such as black~holes.
