REVIEW
Generalized Lorentz invariance with an invariant energy scale
General Relativity and Quantum Cosmology · Submitted 22 Jul 2002 · 37 references
Pith's verdict: The U-map framework is real and useful, but eq. (63), the example offered as meeting all five requirements, does not actually deliver a maximal momentum or a diverging speed of light.
T0 · AI review
Why Pith says this
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Referee report
The paper
The paper claims
Deformed Lorentz symmetry can keep all inertial frames equal
The reading
What carries the argument
The map $U$ on momentum space, and the conjugated generators $K^i = U^{-1} L^{i0} U$ that it induces. $U$ is the object that carries the whole argument: it converts a proposed dispersion relation into a set of transformation laws, it decides whether an invariant energy or a maximal momentum exists (through the behaviour of $E f_1$ and $E/f_3$), and it fixes how momenta compose. Two conditions on $U$ do the load-bearing work — it must be invertible on a physical sector $P_{phys}$ (typically $E < E_{Planck}$ and/or $|p| < E_{Planck}$), and its image must cover $[0,∞]$ in both energy and momentum, since otherwise some boost parameter is bounded, the group property fails, and a preferred frame appears. The second piece of machinery is the composition rule $p_{(1...n)} = U^{-1}[λ/n] (U[p_1;λ](p_1) + … + U[p_n;λ](p_n))$, which replaces ordinary addition of momenta and rescales the deformation parameter by the number of constituents so that macroscopic bodies recover ordinary Lorentz behaviour.
Extended reading notes
Core claim
The central result is that all five properties the authors list — relativity of inertial frames, an invariant energy scale of order the Planck energy, a raised ultra-high-energy cosmic ray threshold, a varying and preferably diverging speed of light, and a maximal momentum — can coexist in a single theory. The construction rests on writing the modified Lorentz generators as $K^i = U^{-1} L^{i0} U$, where $L^{ab}$ are the standard generators and $U$ is a generally non-unitary, non-linear map of momentum space. Any isotropic dispersion relation $E^2 f_1^2(E;λ) - p^2 f_2^2(E;λ) = m^2$ defines such a map via $U(E,p) = (E f_1, p f_2)$, so the dispersion relation becomes the experimental input and the transformation laws the output. An invariant Planck energy appears when $E f_1$ diverges at some finite $E_P$; a maximal momentum appears when $E/f_3$ has a maximum, with $f_3 = f_2/f_1$, and the authors note this forces the speed of light to diverge somewhere. The paper then shows that a single-scale $f_1$ cannot move a threshold far from its special-relativistic value without putting the scale at the threshold itself, and proposes $f_1 = 1/[(1+λ_1 E)(1-λ E)]$ with $λ_1$ much larger than $λ$, which raises the cosmic ray threshold at $N_p λ_1^{-1} ≈ 10^{11}$ GeV while leaving an invariant positive energy $E_P = λ^{-1}$ of order $10^{19}$ GeV.
Load-bearing premise
The multi-particle composition rule, which rescales the deformation parameter to $λ/n$ and is generalized to an arbitrary function $f(n,λ)$ that the authors say 'can be any function leading to suitable limiting properties' — the cosmic ray threshold formula depends entirely on this postulated rule, and the number of quanta in a proton, $N_p$, is left undetermined pending a QCD treatment.
Editorial extensions
If this is right
- Any proposed deformed dispersion relation can be converted into a full set of transformation laws, so the transformation law no longer has to be guessed independently of the dispersion relation.
- A theory with an invariant Planck energy automatically contains three distinguished high-energy states: photons at the invariant energy, particles of infinite rest mass, and 'infinitions' — finite-mass particles that cannot be brought to rest.
- Because a maximal momentum forces the speed of light to diverge at some energy, a theory with a granular short-distance cutoff and a theory with a rising speed of light are not independent options.
- Energy and momentum conservation survives, but additivity does not: conservation is written $p^a \oplus q^a = p'^a \oplus q'^a$, so a particle near the Planck energy becomes progressively harder to accelerate in a collision.
- Defining spatial coordinates as generators of translations in momentum space yields a commutative spacetime, $[x^a, x^b] = 0$, at the price of an energy-dependent effective Planck constant $\hbar = 1 - λ p_0$ in $[x^i, p^j] = δ^{ij}(1 - λ p_0)$.
Reading between the lines
- The two-scale construction $f_1 = 1/[(1+λ_1 E)(1-λ E)]$ is a template rather than a prediction: any function that is approximately one below the Planck energy and diverges there would do the same job, so the framework predicts a family of threshold behaviours rather than a number.
- The energy-dependent $\hbar$ in the real-space formulation suggests a route to laboratory tests: if $\hbar$ falls with momentum, the uncertainty relations themselves become momentum-dependent, which is in principle a different signature from a modified dispersion relation alone.
- The requirement that $U$'s image cover all energies is a sharp selection rule that any candidate quantum-gravity dispersion relation must pass; it could be applied as a filter to dispersion relations derived from other approaches before asking about their phenomenology.
- The proposal that the deformation parameter scales as $λ/n$ for an $n$-constituent system implies that the same physical body would need a different kinematical description depending on how its internal structure is counted, which is a strong and unusual claim about where the quantum-classical boundary sits.
Original abstract
The hypothesis that the Lorentz transformations may be modified at Planck scale energies is further explored. We present a general formalism for theories which preserve the relativity of inertial frames with a non-linear action of the Lorentz transformations on momentum space. Several examples are discussed in which the speed of light varies with energy and elementary particles have a maximum momenta and/or energy. Energy and momentum conservation are suitably generalized and a proposal is made for how the new transformation laws apply to composite systems. We then use these results to explain the ultra high energy cosmic ray anomaly and we find a form of the theory that explains the anomaly, and leads also to a maximum momentum and a speed of light that diverges with energy. We finally propose that the spatial coordinates be identified as the generators of translation in Minkowski spacetime. In some examples this leads to a commutative geometry, but with an energy dependent Planck constant.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
The hypothesis that the Lorentz transformations may be modified at Planck scale energies is further explored. We present a general formalism for theories which preserve the relativity of inertial frames with a non-linear action of the Lorentz transformations on momentum space. Several examples are discussed in which the speed of light varies with energy and elementary particles have a maximum momenta and/or energy. Energy and momentum conservation are suitably generalized and a proposal is made for how the new transformation laws apply to composite systems. We then use these results to explain the ultra high energy cosmic ray anomaly and we find a form of the theory that explains the anomaly, and leads also to a maximum momentum and a speed of light that diverges with energy. We finally propose that the spatial coordinates be identified as the generators of translation in Minkowski spacetime. In some examples this leads to a commutative geometry, but with an energy dependent Planck constant.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The hypothesis that the Lorentz transformations may be modified at Planck scale energies is further explored. | background 0.96 | 0.22 | 0.04 | hedged possibility 0.94 |
| s1 | We present a general formalism for theories which preserve the relativity of inertial frames with a non-linear action of the Lorentz transformations on momentum space. | contribution 0.96 | 0.92 | 0.17 | asserted 0.99 |
| s2 | Several examples are discussed in which the speed of light varies with energy and elementary particles have a maximum momenta and/or energy. | result 0.68 | 0.64 | 0.10 | asserted 0.95 |
| s3 | Energy and momentum conservation are suitably generalized and a proposal is made for how the new transformation laws apply to composite systems. | contribution 0.89 | 0.90 | 0.09 | asserted 0.79 |
| s4 | We then use these results to explain the ultra high energy cosmic ray anomaly and we find a form of the theory that explains the anomaly, and leads also to a maximum momentum and a speed of light that diverges with energy. | result 0.87 | 0.95 | 0.40 | asserted 1.00 |
| s5 | We finally propose that the spatial coordinates be identified as the generators of translation in Minkowski spacetime. | contribution 0.58 | 0.78 | 0.12 | speculative 0.48 |
| s6 | In some examples this leads to a commutative geometry, but with an energy dependent Planck constant. | result 0.61 | 0.76 | 0.10 | hedged possibility 0.60 |
What was examined, and what was not
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- P abstract
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References
How later papers used it
97 later papers cite it
1 later paper by other authors is listed below: 1 compared its own results with it.
Compares with it 1 of 4 papers with this label
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Compared its own energy-momentum undeformed dispersion relations result, derived from a general noncommutative differential geometry construction, with the Deformed Special Relativity proposed in this paper, also known as DSR2.
Observables and Dispersion Relations in k-Minkowski Spacetime (2017) · 1.00 · paraphrased: the licence does not allow quoting
How the literature uses it
78 arXiv papers cite this in 120 sentences
Papers citing it · 56 sentences without a confident label
Uses its method or tool 3 papers
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In this paper, the model we adopt is DSR2, which was proposed and generalized by Magueijo and Smolin [ref] .
Photon Gas Thermodynamics in Doubly Special Relativity · Modified Dispersion Relation For Photon Gas · 0.80
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Let us start with the all important map [ref] [equation] which in explicit form reads [equation] where $n_μ=(1, 0, 0, 0)$ is introduced to express the map in a covariant way and we use the notation $a_μb^μ=(ab)$, $(n p)=p^0$, $(n P)=P^0$.
Effects of a Maximal Energy Scale in Thermodynamics for Photon Gas and Construction of Path Integral · Deformations in Lorentz symmetry: noncommutative spacetime · 0.96
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By using the non-linear Lorentz transformation in the momentum space, the MDR can be compactly written as [ref]
Black hole complementarity with the generalized uncertainty principle in gravity's rainbow · black hole complementarity with GUP in Gravity's Rainbow · 0.80
Compares with it 3 papers
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Thus the DSR model considered in [ref] has a more theoretical motivation and it can be developed starting from the NC phase space variables [ref] whereas the models considered in [ref] are phenomenological in nature and as far as we know, there is no fundamental phase space structures to describe these models.
Effects of a Maximal Energy Scale in Thermodynamics for Photon Gas and Construction of Path Integral · Thermodynamics of photon gas in $κ$-Minkowski spacetime · 0.82
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Finally, we compare our results with the pioneering approach in [ref] .
Observables and Dispersion Relations in k-Minkowski Spacetime · Introduction · 1.00
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In particular it turns out that the invariant dispersion relation for the four-momentum vector is the same as in SR ($E^2 = p^2 + m^2$), which is not the case in most DSR studies [ref] .
Minimum Length - Maximum Velocity · Reference frame invariance of the GUP formalism · 0.91
Cites it as support 1 paper
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Also the speed of light $c$ is an invariant quantity in the DSR model [ref] .
Effects of a Maximal Energy Scale in Thermodynamics for Photon Gas and Construction of Path Integral · Thermodynamics of photon gas in $κ$-Minkowski spacetime · 0.97
Cites it as background 52 papers
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For this purpose we return here to the simple perspective and formalization of the first studies [ref] which noticed that some known deformations of relativistic symmetries, some of the ones studied within the “doubly-special relativity" research programme (see, e.g., Refs. [ref] ), could result in the property that coincidences of events established by nearby observers might not appear as coincidences of events in the coordinatization of spacetime by distant observers.
Modeling transverse relative locality · Introduction · 0.80
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This modification of Special Relativity, which does not introduce a preferred frame but instead postulates the Planck mass as an observer-independent invariant, has become known as “Deformed Special Relativity” (DSR) [ref] .
The Box-Problem in Deformed Special Relativity · Introduction · 0.90
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On the other hand, a relativistic description for the time delay predictions [ref] , i.e., observer independent, is possible within the Double Special Relativity (DSR) framework introduced in [ref] (see also [ref] ).
Rainbows without unicorns: Metric structures in theories with Modified Dispersion Relations · Introduction · 0.86
Discussion
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