#### ${{\mathit \gamma}}$ CHARGE

OKUN 2006 has argued that schemes in which all photons are charged are inconsistent. He says that if a neutral photon is also admitted to avoid this problem, then other problems emerge, such as those connected with the emission and absorption of charged photons by charged particles. He concludes that in the absence of a self-consistent phenomenological basis, interpretation of experimental data is at best difficult.
VALUE ($\mathit e$) CHARGE DOCUMENT ID TECN  COMMENT
$\bf{<1 \times 10^{-46}}$ mixed 1
 2007 B
VLBI Aharonov-Bohm effect
$\bf{<1 \times 10^{-35}}$ single 2
 2005
CMB Isotropy constraint
• • We do not use the following data for averages, fits, limits, etc. • •
$<1 \times 10^{-32}$ single 1
 2007 B
VLBI Aharonov-Bohm effect
$<3 \times 10^{-33}$ mixed 3
 2005
VLBI Smear as function of B$\cdot{}E_{{{\mathit \gamma}} }$
$<4 \times 10^{-31}$ single 3
 2005
VLBI Deflection as function of B$\cdot{}E_{{{\mathit \gamma}} }$
$<8.5 \times 10^{-17}$ 4
 2003
Laser light deflection in B-field
$<3 \times 10^{-28}$ single 5
 1995
CMB For $\Omega _{M}$= 0.3, h${}^{2}$= 0.5
$<5 \times 10^{-30}$ 6
 1994
TOF Pulsar $\mathit f_{1}−\mathit f_{2}$
$<2 \times 10^{-28}$ 7
 1992
$<2 \times 10^{-32}$
 1988
TOF Pulsar $\mathit f_{1}−$ $\mathit f_{2}$ TOF
 1 ALTSCHUL 2007B looks for Aharonov-Bohm phase shift in addition to geometric phase shift in radio interference fringes (VSOP mission).
 2 CAPRINI 2005 uses isotropy of the cosmic microwave background to place stringent limits on possible charge asymmetry of the Universe. Charge limits are set on the photon, neutrino, and dark matter particles. Valid if charge asymmetries produced by different particles are not anticorrelated.
 3 KOBYCHEV 2005 considers a variety of observable effects of photon charge for extragalactic compact radio sources. Best limits if source observed through a foreground cluster of galaxies.
 4 SEMERTZIDIS 2003 reports the first laboratory limit on the photon charge in the last 30 years. Straightforward improvements in the apparatus could attain a sensitivity of $10^{-20}~$e.
 5 SIVARAM 1995 requires that CMB photon charge density not overwhelm gravity. Result scales as $\Omega _{M}~$h${}^{2}$.
 6 RAFFELT 1994 notes that COCCONI 1988 neglects the fact that the time delay due to dispersion by free electrons in the interstellar medium has the same photon energy dependence as that due to bending of a charged photon in the magnetic field. His limit is based on the assumption that the entire observed dispersion is due to photon charge. It is a factor of 200 less stringent than the COCCONI 1988 limit.
 7 See COCCONI 1992 for less stringent limits in other frequency ranges. Also see RAFFELT 1994 note.
Conservation Laws:
ELECTRIC CHARGE ($\mathit Q$)
References:
 ALTSCHUL 2007B
PRL 98 261801 Bound on the Photon Charge from the Phase Coherence of Extragalactic Radiation
 Also
ASP 29 290 Astrophysical Bounds on the Photon Charge and Magnetic Moment
 CAPRINI 2005
JCAP 0502 006 Constraints on the Electrical Charge Asymmetry of the Universe
 KOBYCHEV 2005
AL 31 147 Constraints on the Photon Charge Based on Observations of Extragalactic Sources
 SEMERTZIDIS 2003
PR D67 017701 New Laboratory Technique for Measuring the Photon Charge
 SIVARAM 1995
AJP 63 473 Upper Limit on the Photon Electric Charge from the Cosmic Microwave Background
 RAFFELT 1994
PR D50 7729 Pulsar Bound on the Photon Electric Charge Reexamined
 COCCONI 1992
AJP 60 750 Upper Limits on the Electric Charge of the Photon
 COCCONI 1988
PL B206 705 Upper Limit for Electric Charge of the Photons from the Millisecond Pulsar 1937+21 Observation