Monday, May 18, 2015

Welcome Back/Uncrumpling the Blog

Let me explain...

Like many other undergraduates, the authors of this blog suffer from both inexperience and intense workloads. This was never more true than in the past two years, when we both created and proceeded to actively neglect this blog. Having experienced the phenomenon of failure induced by inactivity, or as they say in baseball, "a strikeout looking," I can say that I do not like the taste it leaves in the mouth. 

Now fortunately, many of us have recently become graduate students. Consider us upgraded, more seasoned, but still active and enthusiastic. We now have among us students of astrophysics, QFT, condensed matter, nonlinear dynamics, biophysics-- to be sure, we have a diverse and capable team. I, at least, will begin writing on this blog, for the exercise if nothing else.
For future reference, my current work will be related to mesoscopic systems, including granular media, elastic and elasto-plastic sheets, yarns, and just about anything in between that provides interesting physical problems for us to think about.

Now, for some content...

Today I want to briefly mention a topic (motivated from a review article, just email me if you want to know more) that is so obvious, so menial, that I am relatively confident that you won't expect it.

How does paper crumple?

How indeed, you say, it seems trivial. But when you consider the idea of a 2-D system, exposed to a uniform force, it becomes a curiously rich playground: why do ridges and vertices appear? Why does nature seem to want to concentrate all of that uniform stress into lower-dimensional structures, when it usually tries to distribute energy randomly?

You've only just begun to scratch the surface. These stress focusing phenomena are present in a wide variety of curious systems, from turbulent flows, to galactic accretion, to dielectric breakdown. When and why does nature decide to put all of its eggs in one basket? From the crumpling perspective, it's easy to tell.

Paper is very close to what we call an isometric sheet. This means that paper is much, much easier to bend than it is to stretch. As a consequence, paper tries to eliminate stretching, which requires that it only bend in one direction. Look at a piece of crumpled paper, and you'll realize that this is true. For the most part, shapes on the paper are only curved in one direction, and flat in the other. This is a very hard constraint to satisfy, and what you end up with when you try to confine a large piece of paper in a small area is the familiar network of ridges and vertices that you know as crumpled paper.

This post was a bit of a warm-up, and in the future I'll be bringing in more commentary-based posts on articles from various journals. I am breaking the arxiv trend, because I don't prefer to live by rules.


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