Matter-gravity couplings and Lorentz violation

Kostelecký, Alan; Tasson, J. D.

doi:10.1103/physrevd.83.016013

Cited by 332 publications

(613 citation statements)

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“…For experiments performed in the Earth's gravitational field, we may neglect such modifications as being common to all experiments. Here, we focus on an isotropic subset of the theory [9] and thereby upon the most poorly constrained flat-space observable (c w ) 00 terms and the (ā w eff ) 0 terms, that are detectable only by gravitational experiments [8,11]. The otherc w − and a w − terms are respectively best constrained by nongravitational experiments or enter the signal as sidereal variations suppressed by 1/c and are neglected here.…”

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confidence: 99%

“…A rigorous comparison between these tests requires the use of a consistent, comprehensive, and predictive phenomenological framework applicable to all experiments. The minimal gravitational SME [8][9][10][11] is just such a framework, and provides the most general way to describe potential low energy Lorentz-and EEPviolating signatures of new physics at high energy scales.…”

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confidence: 99%

“…The superscript w takes the values e, n and p indicating the electron, neutron, and proton, respectively. The motion of a test particle of mass m T , up to O(c −3 ), is that which extremizes the action [9] …”

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confidence: 99%

“…For a quantitative comparison between different redshift tests, we use the standard model extension (SME) [8][9][10][11], which provides the most general way to describe potential low energy Lorentz symmetry-violating (thus EEP-violating) signatures of new physics at high energy scales. We show that all EEP tests are sensitive to the same five terms in the minimal gravitational SME [9][10][11] and, for the first time, comprehensively rule out EEP violation in redshift tests greater than a few parts per million for neutral matter.If two clocks are located at different points in spacetime, they can appear to tick at different frequencies, despite having the same proper frequency ω 0 in their local Lorentz frames. For clocks moving with nonrelativistic velocities v 1 and v 2 in a weak gravitational potential…”

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confidence: 99%

“…Here, we show that the phase accumulated between two atomic wave packets in any interferometer equals the phase between any two clocks running at the atom's Compton frequency following the same paths, proving that atoms are clocks. For a quantitative comparison between different redshift tests, we use the standard model extension (SME) [8][9][10][11], which provides the most general way to describe potential low energy Lorentz symmetry-violating (thus EEP-violating) signatures of new physics at high energy scales. We show that all EEP tests are sensitive to the same five terms in the minimal gravitational SME [9][10][11] and, for the first time, comprehensively rule out EEP violation in redshift tests greater than a few parts per million for neutral matter.…”

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Equivalence Principle and Gravitational Redshift

et al. 2011

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We investigate leading order deviations from general relativity that violate the Einstein equivalence principle in the gravitational standard model extension. We show that redshift experiments based on matter waves and clock comparisons are equivalent to one another. Consideration of torsion balance tests, along with matter wave, microwave, optical, and Mössbauer clock tests, yields comprehensive limits on spin-independent Einstein equivalence principle-violating standard model extension terms at the 10 −6 level.Gravity makes time flow differently in different places. This effect, known as the gravitational redshift, is the original test of the Einstein equivalence principle (EEP) [1] that underlies all of general relativity; its experimental verification [2-6] is fundamental to our confidence in the theory. Atom interferometer (AI) tests of the gravitational redshift [4,6] have a precision 10 000 times better than tests based on traditional clocks [3], but their status as redshift tests has been controversial [7]. Here, we show that the phase accumulated between two atomic wave packets in any interferometer equals the phase between any two clocks running at the atom's Compton frequency following the same paths, proving that atoms are clocks. For a quantitative comparison between different redshift tests, we use the standard model extension (SME) [8][9][10][11], which provides the most general way to describe potential low energy Lorentz symmetry-violating (thus EEP-violating) signatures of new physics at high energy scales. We show that all EEP tests are sensitive to the same five terms in the minimal gravitational SME [9][10][11] and, for the first time, comprehensively rule out EEP violation in redshift tests greater than a few parts per million for neutral matter.If two clocks are located at different points in spacetime, they can appear to tick at different frequencies, despite having the same proper frequency ω 0 in their local Lorentz frames. For clocks moving with nonrelativistic velocities v 1 and v 2 in a weak gravitational potentialThe first term is the gravitational redshift, originally measured [2] by Pound and Rebka in 1960, while the second term is the time dilation due to the clocks' relative motion. The redshift term can be isolated from the time dilation if the clocks' trajectories are known.The state of each clock can be described by a timevarying phase. If two clocks 1 and 2 are synchronized to have identical phase ϕ 0 = 0 at time t = 0, then theirMach-Zehnder clock or atom interferometer. Two otherwise freely falling clocks (or halves of an atomic wavepacket) receive momentum impulses that change their velocity by ±vr. The dashed lines indicate trajectories without gravity.specializing to a homogenous gravitational field so that φ 1 −φ 2 = g· r 12 , with r 12 being the clocks' distance vector and g the local acceleration of free fall. If the clocks are freely falling, then their motion is an extremum of their respective actions [12]Thus δϕ f is proportional to the difference S 1 − S 2 in the...

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Equivalence Principle and Gravitational Redshift

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From Dirac theories in curved space‐times to a variation of Dirac's large–number hypothesis

Jentschura

2014

Annalen der Physik

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Some physicists, even today, may think that it is impossible to connect relativistic quantum mechanics and general relativity [1][2][3]. This impression, however, is false, as demonstrated, among many other recent works, in an article published not long ago in this journal [4]. In order to understand the subtlety, let us remember the meaning of first [5,6], second [7,8], and third quantization (see Refs. [9][10][11]). In first quantization, what was previously a well-defined particle trajectory now becomes smeared and defines a probability density of the quantum mechanical particle. In second quantization, what was previously a well-defined functional value of a physical field at a given space-time point now becomes a field operator, which is subject to quantum fluctuations. E.g., quantum fluctuations about the flat space-time metric can be expressed in terms of the graviton field operator, for which an explicit expression can be found in Eq. (5) of Ref. [8].In third quantization, what was previously a well-defined space-time point now becomes an operator, defining a conceivably noncommutative entity, which describes space-time quantization. E.g., the emergence of the noncommutative Moyal product in quantized string theory is discussed in a particularly clear exposition in Ref. [11], in the derivation leading to Eq. (32) We thus observe that space-time quantization is not necessary, a priori, in order to combine general relativity and quantum mechanics. Indeed, before we could ever conceive to observe effects due to space-time quantization, we should first consider the leading-order coupling of the Dirac particle to a curved spacetime. Space-time curvature is visible on the classical level, and can be treated on the classical level [3]. Deviations from perfect Lorentz symmetry caused by effects other than space-time curvature may result in conceivable anisotropies of spacetime; they have been investigated by Kostelecky et al. in a series of papers (see Refs. [13][14][15] and references therein) and would be visible in tiny deviations of the dispersion relations of the relativistic particles from the predictions of Dirac theory. Measurements on neutrinos [15] can be used in order to constrain the Lorentz-violating parameters. Other recent studies concern the modification of gravitational effects under slight global violations of Lorentz symmetry [16]. Brill and Wheeler [17] were among the first to study the gravitational interactions of Dirac particles, and they put a special emphasis on neutrinos. The motivation can easily be guessed: Neutrinos, at the time, were thought to be massless and transform according to the fundamental ( ) representations of the Lorentz group. Yet, their interactions have a profound impact on cosmology [18]. Being (almost) massless, their gravitational interactions can, in principle, only be formulated on a fully relativistic footing. This situation illustrates a pertinent dilemma: namely, the gravitational potential, unlike the the Coulomb potential, cannot simply be inserted into th...

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