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Small-radius tubular structures have attracted considerable attention in the last few years, and are frequently used in different areas such as Mathematical Physics, Spectral Geometry and Global Analysis.
In this monograph, we analyse Laplace-like operators on thin tubular structures ("graph-like spaces´´), and their natural limits on metric graphs. In particular, we explore norm resolvent convergence, convergence of the spectra and resonances.
Since the underlying spaces in the thin radius limit change, and become singular in the limit, we develop new tools such as
-norm convergence of operators acting in different Hilbert
spaces,
-an extension of the concept of boundary triples to partial
differential operators, and
-an abstract definition of resonances via boundary triples.
These tools are formulated in an abstract framework, independent of the original problem of graph-like spaces, so that they can be applied in many other situations where the spaces are perturbed.

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1 Introduction.- 2 Graphs and associated Laplacians.- 3 Scales of Hilbert space and boundary triples.- 4 Two operators in different Hilbert spaces.- 5 Manifolds, tubular neighbourhoods and their perturbations.- 6 Plumber´s shop: Estimates for star graphs and related spaces.- 7 Global convergence results.

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From the reviews:

"The monograph introduces into the asymptotic analysis of graph-like spaces in the 0-thickness limit and the convergence of associated operators and related objects. ... The author has succeeded to present an extensive self-contained account of a variety of results of both pure and applied character in a way to be very useful for a graduate course or seminar. It is a very successful publication in an active area of interdisciplinary research, where spectral analysis, graph-like spaces and applications interact in a beautiful manner." (Themistocles M. Rassias, Zentralblatt MATH, Vol. 1247, 2012)

"The book represents a valuable contribution to the literature, presenting both its author´s significant contribution to this field and a broad overview of the work done by others. It will be useful to everybody interested in dynamics the quantum one in the first place on such configuration spaces and its numerous applications." (Pavel V. Exner, Mathematical Reviews, January, 2013)

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