There is evidence for an excess in cosmic-ray electrons at about 500 GeV energy , that may be related to dark-matter annihilation .
I have calculated the expected electron contributions from a pulsar and from Kaluza-Klein dark matter , based on a realistic treatment of the electron propagation in the Galaxy .
Both pulsars and dark-matter clumps are quasi-pointlike and few , and therefore their electron contributions at Earth generally have spectra that deviate from the average spectrum one would calculate for a smooth source distribution .
I find that pulsars younger than about 10 ^ { 5 } years naturally cause a narrow peak at a few hundred GeV in the locally observed electron spectrum , similar to that observed .
On the other hand , for a density n _ { c } = 10 { kpc ^ { -3 } } of dark-matter clumps the sharp cut-off in the contribution from Kaluza-Klein particles is sometimes more pronounced , but often smoothed out and indistinguishable from a pulsar source , and therefore the spectral shape of the electron excess is insufficient to discriminate a dark-matter origin from more conventional astrophysical explanations .
The amplitude of variations in the spectral feature caused by dark matter predominantly depends on the density of dark-matter clumps , which is not well known .