Varying electric charge in multiscale spacetimes

Calcagni, Gianluca; Magueijo, João; Fernández, David Rodríguez

doi:10.1103/physrevd.89.024021

Cited by 23 publications

(76 citation statements)

References 146 publications

(278 reference statements)

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“…We will extend the discussion started in [40] for Abelian gauge fields and electrodynamics to non-Abelian fields.…”

Section: B Goals and Resultsmentioning

confidence: 99%

“…In this context, we focus on theories of multiscale spacetimes [4,[30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. These have been proposed either as stand-alone models of exotic geometry [31,32,40,43] or as an effective means to study, in a controlled manner, the change of dimensionality with the probed scale (known as dimensional flow 1 of these models and of their status).…”

Section: A Dimensional Flow and Multiscale Theoriesmentioning

confidence: 99%

“…The theory with fractional derivatives is most promising especially as far as renormalization is concerned but, apart from a general power-counting argument [32], its physical properties have not been studied yet; this will be done in the near future. The scenario with weighted derivatives and the one with q-derivatives, on both of which we focus here, have been analyzed in greater detail both in quantum field theory [32,38,40,41] and cosmology [43] and a wealth of new phenomenology has begun to emerge.…”

Section: A Dimensional Flow and Multiscale Theoriesmentioning

confidence: 99%

“…These have been proposed either as stand-alone models of exotic geometry [31,32,40,43] or as an effective means to study, in a controlled manner, the change of dimensionality with the probed scale (known as dimensional flow 1 of these models and of their status). The model with ordinary derivatives was the first to be proposed [4,46,47] but it cannot be a fundamental theory due to some issues regarding its momentum space and quantization.…”

Section: A Dimensional Flow and Multiscale Theoriesmentioning

confidence: 99%

“…(B) The theories with weighted and q-derivatives have not yet reached a satisfactory level of maturity and much needs to be done to assess their relevance and viability as physical models beyond the standard lore. For instance, the Standard Model has been formulated only in the electromagnetic sector [40,42], models of cosmic inflation and late-time acceleration have been explored only preliminarily [43] and observational constraints on the fundamental scales of the geometry are either heuristic [32] (based qualitatively on toy models of dimensional regularization) or too weak [40]. Moreover, it is not even clear whether a satisfactory perturbative quantum field theory can be formulated at all in the case with weighted derivatives, due to difficulties in defining a predictive Feynman series of scattering processes [41].…”

Section: A Dimensional Flow and Multiscale Theoriesmentioning

confidence: 99%

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Standard Model in multiscale theories and observational constraints

2016

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We construct and analyze the Standard Model of electroweak and strong interactions in multiscale spacetimes with (i) weighted derivatives and (ii) q-derivatives. Both theories can be formulated in two different frames, called fractional and integer picture. By definition, the fractional picture is where physical predictions should be made. (i) In the theory with weighted derivatives, it is shown that gauge invariance and the requirement of having constant masses in all reference frames make the Standard Model in the integer picture indistinguishable from the ordinary one. Experiments involving only weak and strong forces are insensitive to a change of spacetime dimensionality also in the fractional picture, and only the electromagnetic and gravitational sectors can break the degeneracy. For the simplest multiscale measures with only one characteristic time, length and energy scale t Ã , l Ã and E Ã , we compute the Lamb shift in the hydrogen atom and constrain the multiscale correction to the ordinary result, getting the absolute upper bound t Ã < 10 −23 s. For the natural choice α 0 ¼ 1=2 of the fractional exponent in the measure, this bound is strengthened to t Ã < 10 −29 s, corresponding to l Ã < 10 −20 m and E Ã > 28 TeV. Stronger bounds are obtained from the measurement of the fine-structure constant.(ii) In the theory with q-derivatives, considering the muon decay rate and the Lamb shift in light atoms, we obtain the independent absolute upper bounds t Ã < 10 −13 s and E Ã > 35 MeV. For α 0 ¼ 1=2, the Lamb shift alone yields t Ã < 10

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“…We will extend the discussion started in [40] for Abelian gauge fields and electrodynamics to non-Abelian fields.…”

Section: B Goals and Resultsmentioning

confidence: 99%

Section: A Dimensional Flow and Multiscale Theoriesmentioning

confidence: 99%

Section: A Dimensional Flow and Multiscale Theoriesmentioning

confidence: 99%

Section: A Dimensional Flow and Multiscale Theoriesmentioning

confidence: 99%

Section: A Dimensional Flow and Multiscale Theoriesmentioning

confidence: 99%

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Standard Model in multiscale theories and observational constraints

2016

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Multifractional theories: an unconventional review

Calcagni

2017

J. High Energ. Phys.

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323

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We answer to 72 frequently asked questions about theories of multifractional spacetimes. Apart from reviewing and reorganizing what we already know about such theories, we discuss the physical meaning and consequences of the very recent flow-equation theorem on dimensional flow in quantum gravity, in particular its enormous impact on the multifractional paradigm. We will also get some new theoretical results about the construction of multifractional derivatives and the symmetries in the yet-unexplored theory $T_\gamma$, the resolution of ambiguities in the calculation of the spectral dimension, the relation between the theory $T_q$ with $q$-derivatives and the theory $T_\gamma$ with fractional derivatives, the interpretation of complex dimensions in quantum gravity, the frame choice at the quantum level, the physical interpretation of the propagator in $T_\gamma$ as an infinite superposition of quasiparticle modes, the relation between multifractional theories and quantum gravity, and the issue of renormalization, arguing that power-counting arguments do not capture the exotic properties of extreme UV regimes of multifractional geometry, where $T_\gamma$ may indeed be renormalizable. A careful discussion of experimental bounds and new constraints are also presented.Comment: 1+106 pages, 3 figures, 9 tables, 245 references. Review article (with several important novelties) through 72 questions; in some of them, there is text overlap with papers by the author, all indicated in the text. v2: references added, minor typos corrected, answers to questions 01, 59 and 68 expanded. v3: minor typos correcte

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New Standard Model constraints on the scales and dimension of spacetime

Addazi¹,

Calcagni²,

Marcianò³

2018

J. High Energ. Phys.

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Using known estimates for the kaon-antikaon transitions, the mean lifetime of the muon and the mean lifetime of the tau, we place new and stronger constraints on the scales of the multi-fractional theories with weighted and q-derivatives. These scenarios reproduce a quantum-gravity regime where fields live on a continuous spacetime with a scale-dependent Hausdorff dimension. In the case with weighted derivatives, constraints from the muon lifetime are various orders of magnitude stronger than those from the tau lifetime and the kaon-antikaon transitions. The characteristic energy scale of the theory cannot be greater than E * > 3 × 10 2 TeV, and is tightened to E * > 9 × 10 8 TeV for the typical value α = 1/2 of the fractional exponents in the spacetime measure. We also find an upper bound d H < 2.9 on the spacetime Hausdorff dimension in the ultraviolet. In the case with q-derivatives, the strongest bound comes from the tau lifetime, but it is about 10 orders of magnitude weaker than for the theory with weighted derivatives.

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Varying electric charge in multiscale spacetimes

Cited by 23 publications

References 146 publications

Standard Model in multiscale theories and observational constraints

Standard Model in multiscale theories and observational constraints

Multifractional theories: an unconventional review

New Standard Model constraints on the scales and dimension of spacetime

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