Einstein's theory of special relativity is deeply
connected with the notions of *inertial reference frame*, and of
*inertial observer*; nevertheless, there is a special interest in
the consideration of accelerated observers, even in a
special-relativistic context. First, accelerated frames are
historically the germ from which general relativity was born; second,
there are special topics in relativistic theories (such as the
now-famous Unruh effect and the problem of radiation reaction) where
we gain physical insight by a subjective description *made from the
point of view of accelerated observers*. In this thesis, we study
the physics of accelerated observers from several points of
view.

First, we identify the origin of the Unruh and Hawking
effects in the *classical* principle of *perspectival
semantics*, according to which some familiar notions defined in
special-relativistic theories (such as *particle* and
*radiation*) become blurred when they are transported to
accelerated frames or to curved spacetimes. We support our claim by
presenting a classical analogue of the Unruh effect based on the
noninvariance of the notion of electromagnetic radiation when
switching from inertial to accelerated observers. Second, we propose
a general scheme to build an accelerated system of coordinates
(*Märzke--Wheeler coordinates*) adapted to the motion of a
generic accelerated observer. These coordinates reduce to Lorentz
coordinates in a neighborhood of the observer's worldline, and they
generally provide a smooth and consistent foliation of spacetime into
spacelike surfaces. We employ Märzke--Wheeler coordinates to
clarify the relativistic *paradox of the twins*, and we suggest
that field quantization in these coordinates could solve a well-known
inconsistency in the theory of the *circular* Unruh effect
(quantization in rotating coordinates is inconsistent with the
measurements of a rotating detector). Finally, we review the
perennial debate (among relativists and philosophers of physics alike)
on the conventionality of Einstein simultaneity in special relativity,
and we find that the evidence for the *nonconventionality* of
Einstein synchronization appears very compelling. We extend the
discussion to accelerated observers in special relativity and we we
make the case for the conventionality of *Märzke--Wheeler
simultaneity*.

- Dottorato di Ricerca in Fisica, XIII Ciclo, 1997–2000, Università di Parma, Facoltà di Scienze Matematiche, Fisiche e Naturali.
- Tutor: Prof.
**Massimo Pauri**; Coordinator: Prof.**Roberto Coïsson**. Thesis defended on**December 18, 2000**. - Cite:
*Relativity and Acceleration*

M. Vallisneri

thesis, doctorate in physics (University of Parma, Italy, 2000) 96 pp. [+]

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© M. Vallisneri 2014 — last modified on 2012/10/20