Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Searching for a response: the intriguing mystery of Feynman's
  theoretical reference amplifier   We analyze Feynman's work on the response of an amplifier performed at Los
Alamos and described in a technical report of 1946, as well as lectured on at
the Cornell University in 1946-47 during his course on Mathematical Methods.
The motivation for such a work was Feynman's involvement in the Manhattan
Project, for which the necessity emerged of feeding the output pulses of
counters into amplifiers or several other circuits, with the risk of
introducing distortion at each step. In order to deal with such a problem,
Feynman designed a theoretical "reference amplifier", thus enabling a
characterization of the distortion by means of a benchmark relationship between
phase and amplification for each frequency, and providing a standard tool for
comparing the operation of real devices. A general theory was elaborated, from
which he was able to deduce the basic features of an amplifier just from its
response to a pulse or to a sine wave of definite frequency. Moreover, in order
to apply such a theory to practical problems, a couple of remarkable examples
were worked out, both for high-frequency cutoff amplifiers and for
low-frequency ones. A special consideration deserves a mysteriously exceptional
amplifier with best stability behavior introduced by Feynman, for which
different physical interpretations are here envisaged. Feynman's earlier work
then later flowed in the Hughes lectures on Mathematical Methods in Physics and
Engineering of 1970-71, where he also remarked on causality properties of an
amplifier, that is on certain relations between frequency and phase shift that
a real amplifier has to satisfy in order not to allow output signals to appear
before input ones. Quite interestingly, dispersion relations to be satisfied by
the response function were introduced.

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The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
4
The categories of this paper are: cond-mat
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
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The categories of this paper are: math-ph
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: supr-con
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: adap-org