@InProceedings{Hypar_JCCGG2009,
AUTHOR = {Erik D. Demaine and Martin L. Demaine and Vi Hart and
Gregory N. Price and Tomohiro Tachi},
TITLE = {(Non)existence of Pleated Folds:
How Paper Folds Between Creases},
BOOKTITLE = {Abstracts from the 7th Japan Conference on Computational
Geometry and Graphs (JCCGG 2009)},
bookurl = {http://www.jaist.ac.jp/~uehara/JCCGG09/},
ADDRESS = {Kanazawa, Ishikawa, Japan},
MONTH = {November 11--13},
YEAR = 2009,
PAGES = {to appear},
length = {2 pages},
papers = {Hypar_GC},
unrefereed = 1,
paperkind = {abstract},
comments = {The full paper is available as
<A HREF="http://arxiv.org/abs/0906.4747">
arXiv:0906.4747</A>.},
withstudent = 1,
}
At the heart of our results is a new structural theorem characterizing uncreased intrinsically flat surfaces—the portions of paper between the creases. Differential geometry has much to say about the local behavior of such surfaces when they are sufficiently smooth, e.g., that they are torsal ruled. But this classic result is simply false in the context of the whole surface. Our structural characterization tells the whole story, and even applies to surfaces with discontinuities in the second derivative. We use our theorem to prove fundamental properties about how paper folds, for example, that straight creases on the piece of paper must remain piecewise-straight by folding.