Base units of the SI, fundamental constants and modern quantum physics

2005 ◽  
Vol 363 (1834) ◽  
pp. 2177-2201 ◽  
Author(s):  
Christian J Bordé
Keyword(s):  
Quantum Physics ◽  
Rest Mass ◽  
Structure Constant ◽  
Coupling Constants ◽  
Electron Mass ◽  
Boltzmann Constant ◽  
Fundamental Constants ◽  
Planck Constant ◽  
Definition Of ◽  
Base Units

Over the past 40 years, a number of discoveries in quantum physics have completely transformed our vision of fundamental metrology. This revolution starts with the frequency stabilization of lasers using saturation spectroscopy and the redefinition of the metre by fixing the velocity of light c . Today, the trend is to redefine all SI base units from fundamental constants and we discuss strategies to achieve this goal. We first consider a kinematical frame, in which fundamental constants with a dimension, such as the speed of light c , the Planck constant h , the Boltzmann constant k B or the electron mass m e can be used to connect and redefine base units. The various interaction forces of nature are then introduced in a dynamical frame, where they are completely characterized by dimensionless coupling constants such as the fine structure constant α or its gravitational analogue α G . This point is discussed by rewriting the Maxwell and Dirac equations with new force fields and these coupling constants. We describe and stress the importance of various quantum effects leading to the advent of this new quantum metrology. In the second part of the paper, we present the status of the seven base units and the prospects of their possible redefinitions from fundamental constants in an experimental perspective. The two parts can be read independently and they point to these same conclusions concerning the redefinitions of base units. The concept of rest mass is directly related to the Compton frequency of a body, which is precisely what is measured by the watt balance. The conversion factor between mass and frequency is the Planck constant, which could therefore be fixed in a realistic and consistent new definition of the kilogram based on its Compton frequency. We discuss also how the Boltzmann constant could be better determined and fixed to replace the present definition of the kelvin.

Quantum Metrology of Electrical Quantities and Mass

2021 ◽  
Vol 30 (3) ◽  
pp. 17-25
Author(s):  
Mun-Seog KIM ◽  
Dong-Hun CHAE ◽  
Kwang-Cheol LEE
Keyword(s):  
Quantum Physics ◽  
Josephson Effect ◽  
International System ◽  
Quantum Hall ◽  
Fundamental Constants ◽  
Planck Constant ◽  
System Of Units ◽  
Elementary Charge ◽  
Base Units ◽  
New Si

The new International System of Units (SI) became effective on 20 May 2019. In the new SI, the complete system of units can be traced to seven fixed values of the fundamental constants, not to seven base units as in the old system. Electrical metrology has two important quantum mechanical foundations. Here, we introduce the basics and the metrological applications of the Josephson effect and the quantum Hall effect, which play key roles in linking electrical quantities to the fundamental constants, including the Planck constant h, the elementary charge e, and the transition frequency of cesium 133 ΔνCs. Finally, we discuss the redefinition of the kilogram as one of the important examples of electrical metrology based on quantum physics.

scholarly journals Fundamental physics and the fine-structure constant

2017 ◽  
Vol 5 (2) ◽  
pp. 46 ◽  
Author(s):  
Michael Sherbon
Keyword(s):  
Fine Structure ◽  
Structure Constant ◽  
Fine Structure Constant ◽  
Electron Mass ◽  
Fundamental Constants ◽  
Mass Ratio ◽  
Fundamental Physics ◽  
Weak Force ◽  
Strong Force ◽  
Symmetry Principles

From the exponential function of Euler’s equation to the geometry of a fundamental form, a calculation of the fine-structure constant and its relationship to the proton-electron mass ratio is given. Equations are found for the fundamental constants of the four forces of nature: electromagnetism, the weak force, the strong force and the force of gravitation. Symmetry principles are then associated with traditional physical measures.

SPACE-TIME VARIATION OF COUPLING CONSTANTS AND FUNDAMENTAL MASSES

2009 ◽  
Vol 24 (18n19) ◽  
pp. 3342-3353 ◽  
Author(s):  
V. V. FLAMBAUM ◽  
J. C. BERENGUT
Keyword(s):  
Structure Constant ◽  
Big Bang ◽  
Coupling Constants ◽  
Fine Structure Constant ◽  
Fundamental Constants ◽  
Big Bang Nucleosynthesis ◽  
Temporal And Spatial Variation ◽  
Physical Systems ◽  
Temporal And Spatial ◽  
The Universe

We review recent works discussing the effects of variation of fundamental "constants" on a variety of physical systems. These are motivated by theories unifying gravity with other interactions that suggest the possibility of temporal and spatial variation of the fundamental constants in an expanding Universe. The effects of any potential variation of the fine-structure constant and fundamental masses could be seen in phenomena covering the lifespan of the Universe, from Big Bang nucleosynthesis to quasar absorption spectra to modern atomic clocks. We review recent attempts to find such variations and discuss some of the most promising new systems where huge enhancements of the effects may occur.

scholarly journals The kelvin redefinition and its mise en pratique

2016 ◽  
Vol 374 (2064) ◽  
pp. 20150037 ◽  
Author(s):  
B. Fellmuth ◽  
J. Fischer ◽  
G. Machin ◽  
S. Picard ◽  
P. P. M. Steur ◽  
...  
Keyword(s):  
International System ◽  
Thermodynamic Temperature ◽  
Fundamental Constants ◽  
Primary Thermometry ◽  
A Value ◽  
System Of Units ◽  
Mise En Pratique ◽  
Explicit Constant ◽  
Definition Of ◽  
Base Units

In 2018, it is expected that there will be a major revision of the International System of Units (SI) which will result in all of the seven base units being defined by fixing the values of certain atomic or fundamental constants. As part of this revision, the kelvin, unit of thermodynamic temperature, will be redefined by assigning a value to the Boltzmann constant k . This explicit-constant definition will define the kelvin in terms of the SI derived unit of energy, the joule. It is sufficiently wide to encompass any form of thermometry. The planned redefinition has motivated the creation of an extended mise en pratique (‘practical realization’) of the definition of the kelvin ( MeP -K), which describes how the new definition can be put into practice. The MeP -K incorporates both of the defined International Temperature Scales (ITS-90 and PLTS-2000) in current use and approved primary-thermometry methods for determining thermodynamic temperature values. The MeP -K is a guide that provides or makes reference to the information needed to perform measurements of temperature in accord with the SI at the highest level. In this article, the background and the content of the extended second version of the MeP -K are presented.

scholarly journals The watt balance: determination of the Planck constant and redefinition of the kilogram

2011 ◽  
Vol 369 (1953) ◽  
pp. 3936-3953 ◽  
Author(s):  
M. Stock
Keyword(s):  
International System ◽  
Accurate Determination ◽  
Electrical Power ◽  
Planck Constant ◽  
System Of Units ◽  
Macroscopic Quantum Effects ◽  
Watt Balance ◽  
Definition Of ◽  
Base Units

Since 1889, the international prototype of the kilogram has served as the definition of the unit of mass in the International System of Units (SI). It is the last material artefact to define a base unit of the SI, and it influences several other base units. This situation is no longer acceptable in a time of ever-increasing measurement precision. It is therefore planned to redefine the unit of mass by fixing the numerical value of the Planck constant. At the same time three other base units, the ampere, the kelvin and the mole, will be redefined. As a first step, the kilogram redefinition requires a highly accurate determination of the Planck constant in the present SI system, with a relative uncertainty of the order of 1 part in 10 8 . The most promising experiment for this purpose, and for the future realization of the kilogram, is the watt balance. It compares mechanical and electrical power and makes use of two macroscopic quantum effects, thus creating a relationship between a macroscopic mass and the Planck constant. In this paper, the operating principle of watt balance experiments is explained and the existing experiments are reviewed. An overview is given of all available experimental determinations of the Planck constant, and it is shown that further investigation is needed before the redefinition of the kilogram can take place. Independent of this requirement, a consensus has been reached on the form that future definitions of the SI base units will take.

scholarly journals WMAP 5-year constraints on α and me

2009 ◽  
Vol 5 (H15) ◽  
pp. 307-307 ◽  
Author(s):  
Claudia G. Scóccola ◽  
Susana J. Landau ◽  
Héctor Vucetich
Keyword(s):  
Statistical Analysis ◽  
Power Spectrum ◽  
Fundamental Constant ◽  
Structure Constant ◽  
Neutral Hydrogen ◽  
Fine Structure Constant ◽  
Electron Mass ◽  
Fundamental Constants ◽  
Escape Probability ◽  
Data Set

AbstractWe have studied the role of fundamental constants in an updated recombination scenario. We focus on the time variation of the fine structure constant α, and the electron mass me in the early Universe. In the last years, helium recombination has been studied in great detail revealing the importance of taking new physical processes into account in the calculation of the recombination history. The equations to solve the detailed recombination scenario can be found for example in Wong et al. 2008. In the equation for helium recombination, a term which accounts for the semi-forbidden transition 23p–11s is added. Furthermore, the continuum opacity of HI is taken into account by a modification in the escape probability of the photons that excite helium atoms, with the fitting formulae proposed Kholupenko et al 2007. We have analized the dependences of the quantities involved in the detailed recombination scenario on α and me. We have performed a statistical analysis with COSMOMC to constrain the variation of α and me at the time of neutral hydrogen formation. The observational set used for the analysis was data from the WMAP 5-year temperature and temperature-polarization power spectrum and other CMB experiments such as CBI, ACBAR and BOOMERANG and the power spectrum of the 2dFGRS. Considering the joint variation of α and me we obtain the following bounds: -0.011 < $\frac{&#x0394; &#x03B1;}{&#x03B1;_0}$ < 0.019 and -0.068 < $\frac{&#x0394; m_e}{(m_e)_0$ < 0.030 (68% c.l.). When considering only the variation of one fundamental constant we obtain: -0.010 < $\frac{&#x0394; &#x03B1;}{&#x03B1;_0$ < 0.008 and -0.04 < $\frac{&#x0394; m_e}{(m_e)_0}$ < 0.02 (68% c.l.). We compare these results with the ones presented in Landau et al 2008, which were obtained in the standard recombination scenario and using WMAP 3 year release data. The constraints are tighter in the current analysis, which is an expectable fact since we are working with more accurate data from WMAP. The bounds obtained are consistent with null variation, for both α and me, but in the present analysis, the 68% confidence limits on the variation of both constants have changed. In the case of α, the present limit is more consistent with null variation than the previous one, while in the case of me the single parameters limits have moved toward lower values. To study the origin of this difference, we have performed another statistical analysis, namely the analysis of the standard recombination scenario together with WMAP5 data, the other CMB data sets and the 2dFGRS power spectrum. We see that the change in the obtained results is due to the new WMAP data set, and not to the new recombination scenario. The obtained results for the cosmological parameters are in agreement within 1 σ with the ones obtained by the WMAP collaboration, without considering variation of fundamental constants.

scholarly journals DO THE FUNDAMENTAL CONSTANTS CHANGE WITH TIME?

2008 ◽  
Vol 23 (32) ◽  
pp. 2711-2725 ◽  
Author(s):  
NISSIM KANEKAR
Keyword(s):  
Structure Constant ◽  
Low Energy ◽  
Spectral Lines ◽  
Fine Structure Constant ◽  
Electron Mass ◽  
Fundamental Constants ◽  
Mass Ratio ◽  
Advantages And Disadvantages ◽  
Distant Galaxies ◽  
Systematic Effects

Comparisons between the redshifts of spectral lines from cosmologically-distant galaxies can be used to probe temporal changes in low-energy fundamental constants like the fine structure constant and the proton–electron mass ratio. Here, we review the results from, and the advantages and disadvantages of, the best techniques using this approach, before focussing on a new method, based on conjugate satellite OH lines, that appears to be less affected by systematic effects and hence holds much promise for the future.

HOW MANY FUNDAMENTAL CONSTANTS DOES QUANTUM PHYSICS NEED?

2000 ◽  
Vol 15 (06) ◽  
pp. 875-892 ◽  
Author(s):  
J. W. G. WIGNALL
Keyword(s):  
Quantum Electrodynamics ◽  
Quantum Physics ◽  
Inertial Mass ◽  
Lorentz Factor ◽  
Fundamental Constants ◽  
Constant Quantity ◽  
Quantum Phenomena ◽  
De Broglie Wavelength ◽  
Quantum Equations ◽  
Base Units

Of the four familiar constants c, [Formula: see text], [Formula: see text] and ℏ (expressed in SI or other "ordinary" units) used in quantum mechanics and quantum electrodynamics, only three are independent because [Formula: see text], [Formula: see text] and ℏ occur in quantum equations and their predictions only as the ratios [Formula: see text] and [Formula: see text]. If one defines the inertial mass of any particle absolutely and operationally as its rest frame de Broglie frequency, the constant quantity [Formula: see text], where [Formula: see text] is its measured de Broglie wavelength when it has speed v and Lorentz factor γ, then electric charge becomes dimensionless and ℏ disappears from all quantum expressions; classical and quantum equations can then be written in terms of only three fundamental constants — c, the frequency me and the dimensionless e — and involve only two base units, those of length and time. This suggests that quantization rules, whose "scale" is given by ℏ, can also be eliminated from the theoretical framework and that it is therefore possible to construct a single unified theory of classical and quantum phenomena.

scholarly journals Updated fundamental constant constraints from Planck 2018 data and possible relations to the Hubble tension

2020 ◽  
Vol 493 (3) ◽  
pp. 3255-3263 ◽  
Author(s):  
Luke Hart ◽  
Jens Chluba
Keyword(s):  
Rest Mass ◽  
Fundamental Constant ◽  
Structure Constant ◽  
Acoustic Oscillation ◽  
Fine Structure Constant ◽  
Fundamental Constants ◽  
Microwave Background ◽  
Effective Electron ◽  
Cosmological Recombination ◽  
Local Value

ABSTRACT We present updated constraints on the variation of the fine structure constant, αEM, and effective electron rest mass, me, during the cosmological recombination era. These two fundamental constants directly affect the ionization history at redshift z ≃ 1100 and, thus, modify the temperature and polarization anisotropies of the cosmic microwave background (CMB) measured precisely with Planck . The constraints on αEM tighten slightly due to improved Planck 2018 polarization data but otherwise remain similar to previous CMB analysis. However, a comparison with the 2015 constraints reveals a mildly discordant behaviour for me, which from CMB data alone is found below its local value. Adding baryon acoustic oscillation data brings me back to the fiducial value, $m_{\rm e}=(1.0078\pm 0.0067)\, m_{\rm e,0}$, and also drives the Hubble parameter to H0 = 69.1 ± 1.2(in units of ${\rm km \, s^{-1} \, Mpc^{-1} }$). Further adding supernova data yields $m_{\rm e}=(1.0190\pm 0.0055)\, m_{\rm e,0}$ with H0 = 71.24 ± 0.96. We perform several comparative analyses using the latest cosmological recombination calculations to further understand the various effects. Our results indicate that a single-parameter extension allowing a slightly increased value of me (≃3.5σ above me, 0) could play a role in the Hubble tension.

scholarly journals Testing the weak equivalence principle by differential measurements of fundamental constants in the Magellanic Clouds

2019 ◽  
Vol 487 (4) ◽  
pp. 5175-5187 ◽  
Author(s):  
S A Levshakov ◽  
K-W Ng ◽  
C Henkel ◽  
B Mookerjea ◽  
I I Agafonova ◽  
...  
Keyword(s):  
Dark Matter ◽  
Equivalence Principle ◽  
Structure Constant ◽  
Magellanic Clouds ◽  
Fine Structure Constant ◽  
Weak Equivalence ◽  
Electron Mass ◽  
Fundamental Constants ◽  
Weak Equivalence Principle ◽  
The Masses

ABSTRACT Non-standard fields are assumed to be responsible for phenomena attributed to dark energy and dark matter. Being coupled to ordinary matter, these fields modify the masses and/or charges of the elementary particles, thereby violating the weak equivalence principle. Thus, values of fundamental constants such as the proton-to-electron mass ratio, μ, and/or the fine structure constant, α, measured in different environment conditions can be used as probes for this coupling. Here we perform differential measurements of F = μα2 to test a non-standard coupling in the Magellanic Clouds–dwarf galaxies where the overall mass budget is dominated by dark matter. The analysis is based on [C i] and CO lines observed with the Herschel Space Observatory. Since these lines have different sensitivities to changes in μ and α, the combined α and μ variations can be evaluated through the radial velocity offsets, ΔV, between the CO and [C i] lines. Averaging over nine positions in the Magellanic Clouds, we obtain 〈ΔV〉 = −0.02 ± 0.07 km s−1, leading to |ΔF/F| < 2 × 10−7 (1σ), where ΔF/F = (Fobs − Flab)/Flab. However, for one position observed with five times higher spectral resolution we find ΔV = −0.05 ± 0.02 km s−1, resulting in ΔF/F = (−1.7 ± 0.7) × 10−7. Whether this offset is due to changes in the fundamental constants, due to chemical segregation in the emitting gas, or merely due to Doppler noise requires further investigations.

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