Wolfram Mathematica

### Problem with Get'ting files with << as opposed to Get

When trying to import some files into my Mathematica notebook, I wanted to use ToString to specify the file path. Consider the following MWE, where we export some expression to the directory of the notebook, and immediately import it back: In:= Export]<>"output.txt", 2020]; import1 = Import]<>"output.txt"] Out= "2020" This works ....

Micah: 3 hours ago

Physics

### What opposes a smooth motion of a rubber eraser on a glass surface?

A metal block smoothly moves on a glass surface. But a rubber eraser doesn't move very smoothly on a glass surface. In each of the cases, the surfaces are smooth at the macroscopic scale. If the latter is due to friction at the molecular level, how come a metal block ....

Matthew: 3 hours ago

Math

### Seeking very regular $\mathbb Q$-acyclic complexes

This question was raised from a project with Nati Linial and Yuval Peled We are seeking a $3$-dimensional simplicial complex $K$ on $12$ vertices with the following properties a) $K$ has a complete $2$-dimensional skeleton (namely, every triple of vertices form a 2-face of $K$) and it has $165$ $3$-simplices. ....

Isabella: 3 hours ago

Math

### Berry–Esseen bound for operator norm of matrix averages

Is there a Berry–Esseen bound for operator norm of an average of independent random matrices? Suppose $A_1, \dotsc, A_n$ are independent matrices with $\mathbb{E} = I$ (the identity matrix). Is there a Berry–Esseen bound for properly normalized $\lVert\overline{A} - I\rVert_\text{op}$? ....

Addison: 3 hours ago

Academic

### How familiar should I be with research topics of a potential PhD supervisor?

I'm about to finish my master's degree in physics (theoretical physics). I'm applying for several professors in Europe. I want to do my PhD in another field than my master's thesis, but both fields are theoretical and to some extend related. But, I didn't take some relevant courses on this ....

Layla: 3 hours ago

Wolfram Mathematica

### Update an application on the click of a Button

I am finishing my first program in Wolfram Mathematica 10 and if I have almost completed is essentially thanks to this valuable forum soon where I will try to help too. Basically, now I have this problem: to make work a routine I used Button]. Unfortunately, in this program you ....

Eli: 3 hours ago

Computer Science

### Definition of Lagrange nodes in Gmsh

When gmsh uses higher-order tetrahedral elements, there is an underlying Lagrange basis used to specify the map from reference space to the element. I'm trying to load a gmsh mesh of 3rd degree tetrahedral elements, but I can't seem to find any precise documentation on the location of the nodes ....

Charlotte: 3 hours ago

Physics

### Negative Magnus effect?

Supposedly, the Magnus effect, which is responsible for the curve of a curveball, and is the reason that tennis players hit their ground strokes with topspin, only acts above a critical Reynolds number ($\mathrm{Re}=Ud/\nu$, where $U$ is the velocity, $d$ is the diameter, and $\nu$ is the kinematic viscosity) of ....

Greyson: 3 hours ago

Physics

### Do atoms behave like waves?

I've heard someone state that the double slit experiment can also be done with atoms, not just electrons or photons of light. ....

Aaron: 3 hours ago

Biology

### Are there examples of animals being sexually attracted to another species more than to their own?

I just thought that from the perspective of a female domestic cat, a male bobcat probably looks like the archetype of a perfect mate. As tall, strong, muscular and mighty as it possibly gets. Clearly preferable to any of these boring male domestics. Has anyone ever done any research on ....

Thomas: 3 hours ago