(mathematics) Of a boundedlinear operator A, the set of scalar values λ such that the operator A—λI, where I denotes the identity operator, does not have a bounded inverse; intended as a generalisation of the linear algebra sense.
“A climatology of aerosol optical and microphysical properties over the Indian subcontinent from 9 years of Multiangle Imaging Spectroradiometer data.”
“Steady-state fluorescence was measured with a SPEX spectrofluorometer with excitation and emission slits providing a bandpass of 7.2 and 3.6 nm, respectively.”
“Photoluminescence spectra were recorded with a Spex Fluorolog-3 spectrofluorometer and optical absorbance spectra with a Specord M-40 spectrophotometer.”
“Princeton University sent a team that was reputed to be the best equipped, with the latest telescopes and spectroscopes needed for the job.”
“We have found five planets orbiting that star, and with our spectroscopes we found one within the star's habitable zone that has an atmosphere.”
“To isolate harmful food, inspectors from 82 municipal laboratories armed with spectroscopes and radiation detectors comb the city's 69 open-air markets.”