Download G. Fiorentini a

G. Fiorentini
a: a constant that
is not constant?
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The QSO evidence for a  0
What else do we know about a  0 ?
The Oklo natural reactor and the
constancy of a
Ancient meteorites, old stars and a
Possible improvements about a  0
a and other “fundamental constants”
G.Fiorentini
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A Brief History of a
1905 Planck: "it seems to me not completely impossible
that h has the same order of magnitude as e2/c”
1909 Einstein :"It seems to me that we can conclude
from h=e2/c that the same modification of theory that contains
the elementary quantum e as a consequence will also contain the quantum
structure of radiation”
1911 Sommerfeld formally defines a as the ratio of the electrostatic
energy of repulsion between two elementary charges, e, separated
by one Compton wavelength, to the rest energy of a single charge:
e 2 /(  / mc) e 2
1
a


2
mc
c 137
G.Fiorentini
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Garching 2002.
Measurement of a
•Neutron de-Broglie
wavelength
•Quantum Hall effect
•ac Josephson effect
•simple QED bound systems
•electron anomalous magnetic
moment (gold standard)
CODATA [1997]
a(ae)-1=137.03599993(52)
4 p.p.b.
G.Fiorentini
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Inconstant constants:
Dirac ‘Large Number Hypothesis'
In a letter to Nature in 1937 Dirac noted the following
coincidence:
N1 
to
age of universe
39

6

10

e 2 / me c 2
atomic light - crossing time
e2
electric force between proton & electron
N2 
 2.3 1039 
GmN me
Gravitatio nal force between proton & electron
”This suggests that …large numbers are to be regarded not as
constants, but as simple functions of our present epoch,
expressed in atomic units. In this way we avoid the need of
a theory to determine numbers of the order of 1039 “.
Thus if N1 ~N2 one must have varying constants, e.g. G ~ t-1
"...the constancy of the fundamental physical
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constants should be checked G.Fiorentini
in an experiment" - P.A.M Dirac
The QSO evidence for
a  0
•Absorption spectra of
diffuse clouds illuminated
by QSO suggest that
a was smaller in the past:
Da a  10
-5
at 1010y ago
•Assuming linear
dependence:
a / a 
10-15 y-1
G.Fiorentini
J.Webb et al. PRL 87(2001)
Da/a=(0.72+-0.18)10-5
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The method
Obs.
cloud
QSO
Alkali doublet
• Look at absorption spectra of
(fine structure)
P
3/2
diffuse clouds illuminated by QSOs
 mea4
•Identify two (sets of) lines, with
P 1/2
different a dependence,to tell both
 mea2
z and a:
lobs=(1+z) lcloud
•“Alkali” doublets have provided
S 1/2
constraints on Da:
Da /a < 10-4
•Webb et al extended the method to different atomic species,
so as to obtain a larger lever arm (many multiplet method).
G.Fiorentini
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The many
multiplet results
VOLUME 87, NUMBER 9
Many multiplet method: sensitivity gain by observing
lines of different species (e.g. FeII and Mg II).
Lines are in quite different regions: one needs
careful checks for possible miscalibrations
PHYSICAL REVIEW LETTERS
27 AUGUST 2001
Further Evidence for Cosmological Evolution of the Fine Structure Constant
J. K. Webb,' M. T. Murphy,' V V Flambaum,l V A. Dzuba,l J. D. Barrow,2 C. W. Churchill,' J. X.
Prochaska,4 and A. M. Wolfe'
'School of Physics, University of New South Wales, Sydney, NSW 2052, Australia
Z
DAMTP Centre for Mathematical Sciences, Wilberforce Road, Cambridge University, Cambridge CB3 OWA, United Kingdom 'Department of
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Astronomy & Astrophysics, Pennsylvania State University, University Park, Pennsylvania 16802 Carnegie Observatories, 813 Santa Barbara
Street, Pasadena, California 91101
D
Dppartment of Physics and Center for Astrophysics and Space Sciences, University of California, San Diego, C-0424, La
Jolla, California 920923
(Received 29 December 2000; published 9 August 2001)
We describe the results of a search for time variability of the fine structure constant a using
absorption systems in the spectra of distant quasars. Three large optical data sets and two 21 cm and
mm absorption systems provide four independent samples, spanning -23% to 87% of the age of the
universe. Each sample yields a smaller a in the past and the optical sample shows a 40 - deviation: Da/a
= -0.72 -±0.18 X 10-5 over the redshift range 0.5 < z < 3.5. We find no systematic effects which can
explain our results. The only potentially significant systematic effects push Aa/a towards positive
values; i.e., our results would become more significant were we to correct for them.
DOI: 10.1103/PhysRevLett.87.091301
G.Fiorentini
PACS numbers: 98.80.Es, 06.20.Jr, 95.30.Dr, 95.30.Sf
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Summary of information on da/dt
Da/a
Source
Lab
Oklo
Meteorites
2
C
old stars
QSO(doub)
QSO(multi)
CMB
BBN
 4
 
 
 2
 
 4
+ 
 2
 2
Look back
time (Gyr)
4 10-10
1.8
4.5
10
10
11-13
8-12
14
14
z
0
0.1
0.5
1.5
1.5
2-4
1-3
103
109
(da/dt)/a
(y-1)
4 4
 
 
 2
 
 4
+ 
 2
 
t, z connected with Ho=70Km/s/Mpc (WM,WL)=(0.3,0.7)
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Remarks
• Only positive claim from QSO
• Possibly in conflict with Oklo
data
• However:
-non linear evolution of a?
-is a space dependent?
-compensation between changes
of a and of other “fundamental
constants”?
• Radioactive dating of solar system (and/or globular clusters
stars) can reach sensitivity comparable to QSO
G.Fiorentini
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Atomic Clocks
Compare clocks, with frequencies which depend differently on a,
and look for change in relative clock rates.
Best comparison involves H-maser ( HFS of H, n1 a4 )and Hg+
atomic clock (HFS of Hg+, n2 a4 Frel(aZ) ) :
d/dt ln(n1 / n2 ) =(dlna/dt) d/da ln Frel
Measurements over 140 days have given:
(da/dt)/a < 3.7 104 y-1
(Prestage et al PRL 74(1995)3511)
Future measurements should reach 10 y-1 and be capable of
testing the QSO claim.
G.Fiorentini
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Atomic Clocks
in space
Ultimate limit for frequency measurement
is observation time. Cold atoms in lab fall
due to gravity
Atoms in free fall don’t fall, i.e. go to space.
Comparison between atomic clocks
in the Space Station could reach a sensitivity to
(da/dt)/a 10 y-1
and be capable of testing the QSO claim
(ACES: www.cnes.fr/activites/connaissance/physique/aces/1sommaire_aces.htm)
G.Fiorentini
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ACES
Atomic Clocks Ensemble in Space
ACES has been approved to fly on the
International Space Station as an external
payload, starting from 2002 for a period of
one and a half years.
Fundamental physics:
-general relativity tests
-stability of fundamental constants
It consists of the following key elements:
Applications:
•A laser cooled atomic clock "PHARAO" _
contributed to the project by France,
•A microwave link for transfer of time and
-Navigation and positioning
- New concepts for higher performance
GPS systems.
- Geodesy with millimetric precision.
- Precise tracking of remote space
probes.
-Time and frequency metrology
- Comparing and synchronising clocks
frequency _ contributed by ESA
over intercontinental distances to an
•A Hydrogen Maser _ contributed by
Switzerland,
•A laser link for optical transfer of time and
frequency _ contributed by France
www.cnes.fr/activites/connaissance/physique/aces/1
sommaire_aces.htm)
accuracy of 10-16.
G.Fiorentini
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The Oklo phenomenon
•A natural fission reactor
which released about 20 KW
for 700 000 years
about 1.8 Gyr ago
Oklo gives the most strict
bound :

Da/a<10-7
(da/dt)/a <6 10-17
G.Fiorentini
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Footprints of natural fission
•(U235/U238)World= 0.7 %
(U235/U238)OKlo= 0.4 % .
Who has stolen U235?
•U235/U238  3 % 2Gyr ago,
enough for a water moderated
reactor.
•Abundances of Rare Earths
Isotopes at Oklo are similar to
those produced by fission.
G.Fiorentini
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What do we learn
from Oklo ?
Garching 2002.
• Characteristic isotope abundances are due to large sabs of
thermal neutrons (e.g.: n+149Sm-> 150Sm+g)
• sabs large due to resonances near thermal energy*,
• for 149Sm Eres= 97.3 meV today
• At reactor time this resonance was efficient too:
DEres <0.1 eV
• Electromagnetism contributes to nuclear energy levels:
Ecou a/rnuc  MeV.
• Tiny changement of a would spoil the resonance efficiency:
  Da/a < 10-7
* KT = 50 meV at T=600 K
G.Fiorentini
•Shlyakhter Nature (1976), DysonDamour NPB (1996)
Fujii et al NP(2000)
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Oklo and nuclear
clocks
Garching 2002.
•One is comparing nuclear reaction rates now and at Oklo time.
•Essentially one is comparing two nuclear clocks
•These are sensitive both to e.m and nuclear forces:
Ecou a/rnuc
•(Warning: compensation between Da and Drnuc ?)
•Other nuclear clocks are available in nature (reaction rates in
stars, nuclear lifetimes…)
G.Fiorentini
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Garching 2002.
Nuclear lifetimes
and a
• Nuclear lifetimes can depend strongly on a
• e.g.: alpha decay LU238  exp[-104 a]
Nucleus
Decay

(y)
s
1/2
• Merit factor for sensitivity to
9
U
2
10
+120
a
238
change of a is:
9
K
EC
1.3
10
-30
40
s= dln L / dln a
•The highest sensitivity is for
Re187
4 1010 -18000

187Re->187Os+e+n , due to
the very small Q value (2,5 KeV), which depends on the
Coulomb contribution to nuclear levels, which depends on a
Dyson 1972
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Radioactive datings of
the solar system
•The age of old meteorites can be determined
by means of different radioactive methods
(e.g.: U/Th almost insensible to Da, whereas Re/Os strongly
sensitive to Da)
•Each dating determines x= age <Dec_Rate>met.
•One determines age by one method and use the measured
Os/Re value to derive a geochemical value of Re decay rate
•Geochemistry

<L>met. =(2.400.02)10-11 y-1
•Lab.measurement 
Lpres =(2.360.04)10-11 y-1
•Comparison

[apres- <a>met ]/ apres= (1  1)10-6
+ linear evol.

a / a  (0.40.5)10-15 y-1
Sensitivity worse than Oklo, however comparable to QSO
G.Fiorentini
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12C
synthesis
•Our existence relies on a nuclear accident,
a suitably placed 12C excited level which
makes carbon synthesis efficient in stars
at kT10KeV, through
a+a+a-> 12C* -> 12C +g
•We measure now: dm = m12*-3ma =379.5KeV
• dm contains a Coulomb contribution Ecou a/rnuc .
•We see 12C in old stars. This implies the resonance has not
moved by more than kT=10KeV---> Da/a < 10-2
• Conceptually, the same argument as Oklo.
• Sensitivity is worse than Oklo, due to larger kT
• However it probes older times, t 10 Gyr
G.Fiorentini
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Radioactive dating of
old stars
•Radioactive dating has been extended
to the oldest stars in the Galaxy,
essentially by means of Th decay.
•Recently measurement of a stellar age
by means of U decay has been obtained
Cayrel et al.
Nature 409(2001)
•Significant improvement, since U decays
faster and initial abundance is better estimated:
TCayrel = (12.5 +- 3)Gyr
•This nuclear clock depends on a.
G.Fiorentini
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Measurement of stellar
age from U decay
Cayrel et al.
Nature
409(2001)
G.Fiorentini
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Comparison of stellar clocks
•The evolution of globular
cluster provides a standard
chronometer of the Galaxy.
•This method is substantially
insensitive to a changes.
•The agreement with the
nuclear clock within
(errors of) 3 Gyr implies:
Da/a<  at t=12Gyr
G.Fiorentini
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a and the CMB
PHYSICAL REVIEW D, VOLUME 62, 123508
ChangeGarching
a 2002.
change BE
change recomb.time
change z(last scat.)
 change l(peak)
Looking for a varying a in the cosmic microwave background
P. P. Avelino,1,2,* C. J. A. P. Martins,3,1,t G. Rocha,1,4,* and P. Vianal°s°§
1
Centro de Astrofzsica, Universidade do Porto, Run das Estrelas s/n, 4150-762 Porto, Portugal
2
Departamento de Fisica da Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal 3 Department of Applied
Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 OWA, United Kingdom
4
Department of Physics, University of Oxford, Nuclear & Astrophysics Laboratory, Keble Road, Oxford OXI 3RH, United Kingdom
5
Departamento de Matemntica Aplicada da Faculdade de Ciencias da Universidade do Porto, Rua das Taipas 135,
4050 Porto, Portugal
(Received 29 August 2000; published 21 November 2000)
We perform a likelihood analysis of the recently released BOOMERanG and MAXIMA data, allowing
for the possibility of a time-varying fine-structure constant. We find that in general these data prefer a value
of a that was smaller in the past (which is in agreement with measurements of a from quasar observations).
However, there are some interesting degeneracies in the problem which imply that strong statements about a
cannot be made using this method until independent accurate determinations of flbhz and Ho are available. We
also show that a preferred lower value of a comes mainly from the data points around the first Doppler peak,
whereas the main effect of the high-/ data points is to increase the preferred value for flbhz (while also
tightening the constraints on flo and Ho). We comment on some implications of our results.
A lower a seemed preferred by CMB. See however update...
G.Fiorentini
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a and BBN
VOLUME 33, NUMBER 4
PHYSICAL REVIEW D
15 FEBRUARY 1986
Time variation of fundamental constants, primordial nucleosynthesis,
and the size of extra dimensions
E..W. Kolb, M.J. Perry and T.P. Walker
(Received 23 Septeber 1985)
In theories with extra dimensionsm the dependence of fundamental
constants on the volume of the compact space allows one to use
primordial nucleosynthesis to probe the structure of compact
dimensions during the first few minutes after the big bang. Requiring
the yield of primordial 4He to be within acceptable limits, we find
that in ten-dimensional superstring models the size of the extra
dimensions during primordial nucleosynthesis must have been within
0.5% of their current value, while in Kaluza-Klein models the extra
dimensions must have been within 1% of theri current value.
for the possibility of a time-varying fine-structure constant. We find
that in general these data prefer a value of a that was smaller in the
past (which is in agreement with measurements of a from quasar
G.Fiorentini
Change a

change
mn-mp

change Nn
at freezeout

change 4He

Da/a<2
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Garching 2002.
a , CMB and BBN : update
Astro-ph/0102144
Early-universe constraints on a time-varying fine structure
constant
P. P. Avelino 1,2 , S. Esposito 3,4 , G. Mangano 4 , C. J. A. P. Martins' 5 A.
Melchiorri 6 , G. Miele 4 , O. Pisanti 4 , G. Rocha l ,6 , and P.T.P. Viana l J
Higher-dimensional theories have the remarkable feature of
predicting a time (and hence redshift) dependence of the
`fundamental' four dimensional constants on cosmological
timescales. In this paper we update the bounds on a possible
variation of the fine structure constant a at the time of BBN
(z10) and CMB (z10 3). Using the recently-released highresolution CMB anisotropy data and the latest estimates of
primordial abundances of 4 He and D, we do not find evidence
for a varying a at more than one-sigma level at either epoch.
BBN:
CMB:
Da
a
Da
a
 1 10  2
 5 10  2
G.Fiorentini
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a is not alone
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
The idea that several “fundamental constants” can vary on
cosmological scales goes back to Dirac (1937)
Time variations of “fundamental Constants”are natural in
theories with extra dimensions (see Marciano, Dvali,
Zaldarriaga…)
GUT require that an evolution of aem be accompanied by
changes of ai, or GUT is occasional.
G.Fiorentini
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Concluding remarks

Actually unification requires changes of aem to be accompanied
by a much stronger change in strong interaction parameters
(Calmet, Fritsch, Langacker….)
4 Daem/aem
Several consequences, since Mp,nLqcd Mp2Lqcd
DLqcd/Lqcd

• Signal/bounds on daem/dt give info on other interactions
• Analysis have to incorporate DLqcd as well as Daem
• Dedicated experiments are needed
The constancy of the fundamental physical
constants should be checked in an experiment"
- P.A.M Dirac (1937)
G.Fiorentini
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