# Quantum Calculus

Calculus without limits
##### Cohomology in six lines
Here is the code to compute a basis elements of the cohomology...
##### Green Star Formula
We found a formula of the green function entries g(x,y). Where g...
When replacing the circle group with the dyadic group of integers, the...
##### A Perron-Frobenius Vector to Wu Characteristic
The Wu characteristic of a simplicial complex is the eigenvalue of an...
##### Is there physics for the connection Laplacian?
The classical potential $V(x,y) = 1/|x-y|$ has infinite range which violently clashes...
##### Quest for a Green Function Formula
A simplicial complex G, a finite set of non-empty sets closed under...
##### More Green Function Values
We have seen that for a finite abstract simplicial complex $G$, the...
##### Isospectral Simplicial Complexes
One can not hear a complex! After some hope that some kind...
##### Wenjun Wu, 1919-2017
According to Wikipedia, the mathematician Wen-Tsun Wu passed away earlier this year....
##### Hearing the shape of a simplicial complex
A finite abstract simplicial complex has a natural connection Laplacian which is...
##### Aspects of Discrete Geometry
The area of discrete geometry is a maze. There are various flavors.
##### Symmetry via Ergodic Theory
One of the attempts to quantize space without losing too much symmetry...
##### What is geometry?
In the context of quantum calculus one is interested in discrete structures...
##### Jones Calculus
The mathematics of evolving fields with two complex components is known already...
##### A quaternion valued elliptic complex
This blog entry delivers an other example of an elliptic complex which...
##### Discrete Atiyah-Singer and Atiyah-Bott
As a follow-up note to the strong ring note, I tried between...
##### Strong Ring of Simplicial Complexes
The strong ring is a category of geometric objects G which are...
##### The Dirac operator of Products
Implementing the Dirac operator D for products $latex G \times H$ of...
##### Do Geometry and Calculus have to die?
In the book 'This Idea Must Die: Scientific Theories That Are Blocking...
##### The Two Operators
The strong ring The strong ring generated by simplicial complexes produces a...
##### Space and Particles
Elements in the strong ring within the Stanley-Reisner ring still can be...
##### Graph limits with Mass Gap
The graph limit We can prove now that the graph limit of...
##### One ring to rule them all
Arithmetic with networks The paper "On the arithmetic of graphs" is posted....
##### Three Kepler Problems
Depending on scale, there are three different Kepler problems: the Hydrogen atom,...
##### More about the ring of networks
The dual multiplication of the ring of networks is topological interesting as...
##### Unique prime factorization for Zykov addition
We give two proofs that the additive Zykov monoid on the category...
##### Hardy-Littlewood Prime Race
The Hardy-Littlewood race has been running now for more than a year...
##### The Hydrogen trace of a complex
Motivated by the Hamiltonian of the Hydrogen atom, we can look at...
##### The quantum plane
Update of May 27, 2017: I dug out some older unpublished slides...
##### A mass gap in the Barycentric limit
The Barycentric limit of the density of states of the connection Laplacian...
##### Tensor Products Everywhere
The tensor product is defined both for geometric objects as well as...
##### Functional integrals on finite geometries
We look at examples of functional integrals on finite geometries.
##### The finitist bunker
As Goedel has shown, mathematics can not tame the danger that some...
##### The Helmholtz Hamiltonian System
As we have an internal energy for simplicial complexes and more generally...
##### Energy theorem for Grothendieck ring
Energy theorem The energy theorem tells that given a finite abstract simplicial...
##### From Affinity over Vis Viva to Energy
The history of the developent of energy and entropy is illustrated. This...
##### Helmholtz free energy for simplicial complexes
Over spring break, the Helmholtz paper [PDF] has finished. (Posted now on...
##### Who is this famous person?
A rather unfamiliar picture of a famous mathematician/physisist.
##### Energy, Entropy and Gibbs free Energy
Energy U and Entropy S are fundamental functionals on a simplicial complex...
##### Shannon Entropy and Euler Characteristic
Entropy is the most important functional in probability theory, Euler characteristic is...
##### A Gauss-Bonnet connection
An experimental observation : the sum over all Green function values is...
##### Sphere spectrum paper
The sphere spectrum paper is submitted to the ArXiv. A local copy....
##### Spectra of Sums of Networks
What happens with the spectrum of the Laplacian $latex L$ if we...
##### A ring of networks
Assuming the join operation to be the addition, we found a multiplication...
##### Arithmetic with networks
The join operation on graphs produces a monoid on which one can...
##### Sphere Spectrum
This is a research in progress note while finding a proof of...
##### Partial differential equations on graphs
During the summer and fall of 2016, Annie Rak did some URAF...
##### Unimodularity theorem slides
Here are some slides about the paper. By the way, an appendix...
##### From the Christmas Theorem to Particle Physics
The Christmas Theorem Because Pierre de Fermat announced his two square theorem...
##### The unimodularity theorem proof
The proof of the unimodularity theorem is finished.
##### Dimension: from discrete to general metric spaces
This is an informal overview over definitions of dimension, both in the...
##### Euler and Fredholm
The following picture illustrates the Euler and Fredholm theme in the special...
##### The Unimodularity Theorem for CW Complexes
The unimodularity theorem equates a fredholm determinant with a product of indices....
##### Quantum calculus talk of 2013
Just uploaded a larger version of my 2013 Pecha-Kucha talk "If Archimedes...
##### On Bowen-Lanford Zeta Functions
Zeta functions are ubiquitous in mathematics. One of the many zeta functions,...
##### The Kustaanheimo prime
Paul Kustaanheimo (1924-1997) was a Finnish astronomer and mathematician. In celestial mechanics,...
##### Particles and Primes, Counting and Cohomology
Source: Pride and Prejudice, 2005 Judy Dench plays the role of Lady...
##### Counting and Cohomology
There are various cohomologies for finite simplicial complexes. If the complex is...
##### Quaternions and Particles
The standard model of particle physics is not so pretty, but it...
##### Bosonic and Fermionic Calculus
Traditional calculus often mixes up different spaces, mostly due to pedagogical reasons....
##### Interaction cohomology
Classical calculus we teach in single and multi variable calculus courses has...
##### Wu Characteristic
Update: March 8, 2016: Handout for a mathtable talk on Wu characteristic....
##### Barycentric refinement
A finite graph has a natural Barycentric limiting space which can serve...
##### Level surfaces and Lagrange
How to define level surfaces or solve extremization problems in a graph....
##### Why quantum calculus?
Quantum calculus is easy to learn, allows experimentation with small worlds and...
##### Calculus on graphs
Calculus on graphs is a natural coordinate free frame work for discrete...

## Isospectral Simplicial Complexes

One can not hear a complex! After some hope that some kind of algebraic miracle allows to recover the complex from the spectrum (for example by looking for the minimal polynomial which an eigenvalue has and expecting that the factorization reflects some order structure in the abstract simplicial complex), I wondered whether there is an argument proving that that there … ….

## Wenjun Wu, 1919-2017

According to Wikipedia, the mathematician Wen-Tsun Wu passed away earlier this year. I encountered some mathematics developed by Wu when working on Wu characteristic. See the Slides and the paper on multi-linear valuations. There is an other paper on this in preparation, especially dealing with the cohomology belonging to Wu characteristics. Just as a reminder, the Wu characteristic of a … ….

## Hearing the shape of a simplicial complex

A finite abstract simplicial complex has a natural connection Laplacian which is unimodular. The energy of the complex is the sum of the Green function entries. We see that the energy is also the number of positive eigenvalues minus the number of negative eigenvalues. One can therefore hear the Euler characteristic. Does the spectrum determine the complex?