CONSERNING THE REALITY OF VACUUM FIELD (L.R.)
http://www.nature.com/news/2011/110603/full/news.2011.346.html
Moving mirrors make light from nothing
Geoff Brumfiel
Researchers claim to have produced sought-after quantum effect.
A moving mirror can generate light from a vacuum.
Phil.M.Rogers/Alamy
A team of physicists is claiming to have coaxed sparks from the vacuum of empty space1. If verified, the finding would be one of the most unusual experimental proofs of quantum mechanics in recent years and "a significant milestone", says John Pendry, a theoretical physicist at Imperial College London who was not involved in the study.
The researchers, based at the Chalmers University of Technology in Gothenburg, Sweden, will present their findings early next week at a workshop in Padua, Italy. They have already posted a paper on the popular pre-print server arXiv.org, but have declined to talk to reporters because the work has not yet been peer-reviewed. High-profile journals, including Nature, discourage researchers from talking to the press until their findings are ready for publication.
Nevertheless, scientists not directly connected with the group say that the result is impressive. "It is a major development," says Federico Capasso, an experimental physicist at Harvard University in Cambridge, Massachusetts, who has worked on similar quantum effects.
At the heart of the experiment is one of the weirdest, and most important, tenets of quantum mechanics: the principle that empty space is anything but. Quantum theory predicts that a vacuum is actually a writhing foam of particles flitting in and out of existence.
The existence of these particles is so fleeting that they are often described as virtual, yet they can have tangible effects. For example, if two mirrors are placed extremely close together, the kinds of virtual light particles, or photons, that can exist between them can be limited. The limit means that more virtual photons exist outside the mirrors than between them, creating a force that pushes the plates together. This 'Casimir force' is strong enough at short distances for scientists to physically measure it.
From virtual to real
For decades, theorists have predicted that a similar effect can be produced in a single mirror that is moving very quickly. According to theory, a mirror can absorb energy from virtual photons onto its surface and then re-emit that energy as real photons. The effect only works when the mirror is moving through a vacuum at nearly the speed of light — which is almost impossible for everyday mechanical devices.
Per Delsing, a physicist at the Chalmers University of Technology, and his colleagues circumvented this problem using a piece of quantum electronics known as a superconducting quantum interference device (SQUID), which is extraordinarily sensitive to magnetic fields.
The team fashioned a superconducting circuit in which the SQUID effectively acted as a mirror. Passing a magnetic field through the SQUID moved the mirror slightly, and switching the direction of magnetic field several billion times per second caused it to 'wiggle' at around 5% the speed of light, a speed great enough to see the effect.
The result was a shower of microwave photons shaken loose from the vacuum, the team claims. The group's analysis shows that the frequency of the photons was roughly half the frequency at which they wiggled the mirror — as was predicted by quantum theory.
Capasso calls the experiment "very clever". He doubts that the effect has any practical use because it doesn't generate large numbers of photons, but he considers it a nice demonstration of quantum mechanics. He still hopes to see a moving piece of metal generate detectable light from the vacuum, and believes that micromechanical systems may eventually be able to reach such speeds.
Pendry says that the result, if it stands up, is bound to generate excitement. "Work in this area stirs considerable passion in the breasts of physicists."
References
Wilson, C. M. et al.
Preprint at http://arxiv.org/abs/1105.4714 (2010)
http://www.nature.com/news/2011/110603/full/news.2011.346.html
Moving mirrors make light from nothing
Geoff Brumfiel
Researchers claim to have produced sought-after quantum effect.
A moving mirror can generate light from a vacuum.
Phil.M.Rogers/Alamy
A team of physicists is claiming to have coaxed sparks from the vacuum of empty space1. If verified, the finding would be one of the most unusual experimental proofs of quantum mechanics in recent years and "a significant milestone", says John Pendry, a theoretical physicist at Imperial College London who was not involved in the study.
The researchers, based at the Chalmers University of Technology in Gothenburg, Sweden, will present their findings early next week at a workshop in Padua, Italy. They have already posted a paper on the popular pre-print server arXiv.org, but have declined to talk to reporters because the work has not yet been peer-reviewed. High-profile journals, including Nature, discourage researchers from talking to the press until their findings are ready for publication.
Nevertheless, scientists not directly connected with the group say that the result is impressive. "It is a major development," says Federico Capasso, an experimental physicist at Harvard University in Cambridge, Massachusetts, who has worked on similar quantum effects.
At the heart of the experiment is one of the weirdest, and most important, tenets of quantum mechanics: the principle that empty space is anything but. Quantum theory predicts that a vacuum is actually a writhing foam of particles flitting in and out of existence.
The existence of these particles is so fleeting that they are often described as virtual, yet they can have tangible effects. For example, if two mirrors are placed extremely close together, the kinds of virtual light particles, or photons, that can exist between them can be limited. The limit means that more virtual photons exist outside the mirrors than between them, creating a force that pushes the plates together. This 'Casimir force' is strong enough at short distances for scientists to physically measure it.
From virtual to real
For decades, theorists have predicted that a similar effect can be produced in a single mirror that is moving very quickly. According to theory, a mirror can absorb energy from virtual photons onto its surface and then re-emit that energy as real photons. The effect only works when the mirror is moving through a vacuum at nearly the speed of light — which is almost impossible for everyday mechanical devices.
Per Delsing, a physicist at the Chalmers University of Technology, and his colleagues circumvented this problem using a piece of quantum electronics known as a superconducting quantum interference device (SQUID), which is extraordinarily sensitive to magnetic fields.
The team fashioned a superconducting circuit in which the SQUID effectively acted as a mirror. Passing a magnetic field through the SQUID moved the mirror slightly, and switching the direction of magnetic field several billion times per second caused it to 'wiggle' at around 5% the speed of light, a speed great enough to see the effect.
The result was a shower of microwave photons shaken loose from the vacuum, the team claims. The group's analysis shows that the frequency of the photons was roughly half the frequency at which they wiggled the mirror — as was predicted by quantum theory.
Capasso calls the experiment "very clever". He doubts that the effect has any practical use because it doesn't generate large numbers of photons, but he considers it a nice demonstration of quantum mechanics. He still hopes to see a moving piece of metal generate detectable light from the vacuum, and believes that micromechanical systems may eventually be able to reach such speeds.
Pendry says that the result, if it stands up, is bound to generate excitement. "Work in this area stirs considerable passion in the breasts of physicists."
References
Wilson, C. M. et al.
Preprint at http://arxiv.org/abs/1105.4714 (2010)
THE PHYSICAL SENSE OF PLANCK CONSTANT IN MODEL OF "VACUUM CRYSTAL"
Planck constant as energy of unit mode of vacuum field
Planck constant as energy of unit mode of vacuum field
Einstein relation for spectral density of radiation energy ρ in the conditions of thermal balance – is given by:
N2 + B21 ρN2 = B12 ρN1 (1)
Here B12 = B21 = B – probabilities of transitions up and down under the influence of an electromagnetic field, A21 = A – probability of spontaneous transition from upper level on lower one.
Expression (1) can be written in the form:
N2(ρ + A/B) = ρN1 (1a)
Taking account of Boltzman distributions of occupation numbers N1 and N2, and also of Rayleigh-Jeans formula, the relation can be derived:
A/B = 8πһ/λ³ = n(λ)һ (2)
where
n(λ) = 8π/λ³ (3)
– volume density of modes with wave length λ.
Unlike an electromagnetic field which causes transitions both downwards and upwards, the vacuum field is capable to cause only transitions from upper level onto lower one.
Let's try to explain this "asymmetry" of action of a vacuum field by means of the model of "crystal vacuum” or “a world crystal” [1].
This excitation field, which causes spontaneous transitions, can be presented as analogue of phonon field in usual crystal. By assumption “acoustic phonons“ have place here, they can be identified with “longitudinal photons” in quantum electrodynamics which are responsible for Coulomb interaction. But Coulomb field is created by the ordered stream of longitudinal photons from a source whereas spontaneous transitions are caused by fluctuations of a chaotic field of longitudinal photons.
Why the stationary “electronic cloud” in atom does not transit from the upper state onto lower one, in spite of the fact that it is induced to such transition by force of an attraction of kernel?
It is because the wave structure of this "cloud", according to Schroedinger equation, has its spatial form steady against change. The electronic cloud could transit to lower stationary state only after this steady structure has been destabilised, destroyed. However such destroying demands an expense of certain energy.
The model of "vacuum crystal” allows to explain the origin of energy which is necessary for spontaneous transition. The electronic cloud in atom is constantly influenced by a chaotic vacuum phonon field ρvac. Casual phases coincidence of these phonons, creating a fluctuation of certain type, leads to disintegration (decay) of stationary state and to transition of electronic cloud (under Coulomb potential action) in lower stationary state. Such transition is accompanied by emission electromagnetic wave train ("photon") which frequency is equal to a difference of frequencies of stationary conditions.
N2 (ρ + ρvac) = ρN1 (5)
According to this expression, ρvac could be interpreted as volume spectral density of energy of the hypothetical vacuum field responsible for "spontaneous" transitions. As n(λ) according to (3), represents modes density, so Planck constant һ means energy of an individual mode of vacuum “phonon” fields.
The volume density of energy of this field in the range of frequencies ∆ν is:
∆ε = ρvac ∆ν = ρvac ∆(c/λ)
Substitution of (4) and (3) into this expression gives:
dε/dλ = 8πһc/λ(5) (6)
Full energy in volume unit (or the pressure of field P) may be defined by integration on all possible wave lengths. If to denote a vacuum lattice constant as a, the minimum wave length will be: λ0 = 2а. Disregarding reduction of modes density in comparison with (3) when λ → a, it is possible to receive the rough (obviously overrated) estimate of pressure, by means of integration (6) from λ0 to ∞:
P = ∫dε = 4πһс/а(4) (7)
Thus, volume energy density of “phonon” vacuum field (it is the same as the field of "longitudinal photons”) is inverse proportional 4-th degrees of vacuum crystal lattice constant .
If our assumption is true: the lattice knots are formed by quarks – the lattice constant should be several times more than characteristic diameter of quark,
i.e. а ~ 10(-18) m.
Substitution of this value in (7) gives an estimation of energy density:
P ~ 10(31) J/m³ = 10(31) N/m²
Energy of phonon vacuum field in atom volume [ra ≈ 10(-10) m] thus will be Еa ~ 10(20) eV.
Such a great scale of energy cannot serve as a refutation of the offered model: spontaneous transitions are caused not by field itself, but only by field fluctuations.
N2 + B21 ρN2 = B12 ρN1 (1)
Here B12 = B21 = B – probabilities of transitions up and down under the influence of an electromagnetic field, A21 = A – probability of spontaneous transition from upper level on lower one.
Expression (1) can be written in the form:
N2(ρ + A/B) = ρN1 (1a)
Taking account of Boltzman distributions of occupation numbers N1 and N2, and also of Rayleigh-Jeans formula, the relation can be derived:
A/B = 8πһ/λ³ = n(λ)һ (2)
where
n(λ) = 8π/λ³ (3)
– volume density of modes with wave length λ.
Unlike an electromagnetic field which causes transitions both downwards and upwards, the vacuum field is capable to cause only transitions from upper level onto lower one.
Let's try to explain this "asymmetry" of action of a vacuum field by means of the model of "crystal vacuum” or “a world crystal” [1].
This excitation field, which causes spontaneous transitions, can be presented as analogue of phonon field in usual crystal. By assumption “acoustic phonons“ have place here, they can be identified with “longitudinal photons” in quantum electrodynamics which are responsible for Coulomb interaction. But Coulomb field is created by the ordered stream of longitudinal photons from a source whereas spontaneous transitions are caused by fluctuations of a chaotic field of longitudinal photons.
Why the stationary “electronic cloud” in atom does not transit from the upper state onto lower one, in spite of the fact that it is induced to such transition by force of an attraction of kernel?
It is because the wave structure of this "cloud", according to Schroedinger equation, has its spatial form steady against change. The electronic cloud could transit to lower stationary state only after this steady structure has been destabilised, destroyed. However such destroying demands an expense of certain energy.
The model of "vacuum crystal” allows to explain the origin of energy which is necessary for spontaneous transition. The electronic cloud in atom is constantly influenced by a chaotic vacuum phonon field ρvac. Casual phases coincidence of these phonons, creating a fluctuation of certain type, leads to disintegration (decay) of stationary state and to transition of electronic cloud (under Coulomb potential action) in lower stationary state. Such transition is accompanied by emission electromagnetic wave train ("photon") which frequency is equal to a difference of frequencies of stationary conditions.
N2 (ρ + ρvac) = ρN1 (5)
According to this expression, ρvac could be interpreted as volume spectral density of energy of the hypothetical vacuum field responsible for "spontaneous" transitions. As n(λ) according to (3), represents modes density, so Planck constant һ means energy of an individual mode of vacuum “phonon” fields.
The volume density of energy of this field in the range of frequencies ∆ν is:
∆ε = ρvac ∆ν = ρvac ∆(c/λ)
Substitution of (4) and (3) into this expression gives:
dε/dλ = 8πһc/λ(5) (6)
Full energy in volume unit (or the pressure of field P) may be defined by integration on all possible wave lengths. If to denote a vacuum lattice constant as a, the minimum wave length will be: λ0 = 2а. Disregarding reduction of modes density in comparison with (3) when λ → a, it is possible to receive the rough (obviously overrated) estimate of pressure, by means of integration (6) from λ0 to ∞:
P = ∫dε = 4πһс/а(4) (7)
Thus, volume energy density of “phonon” vacuum field (it is the same as the field of "longitudinal photons”) is inverse proportional 4-th degrees of vacuum crystal lattice constant .
If our assumption is true: the lattice knots are formed by quarks – the lattice constant should be several times more than characteristic diameter of quark,
i.e. а ~ 10(-18) m.
Substitution of this value in (7) gives an estimation of energy density:
P ~ 10(31) J/m³ = 10(31) N/m²
Energy of phonon vacuum field in atom volume [ra ≈ 10(-10) m] thus will be Еa ~ 10(20) eV.
Such a great scale of energy cannot serve as a refutation of the offered model: spontaneous transitions are caused not by field itself, but only by field fluctuations.