Posts tagged with complex numbers

> plot( polyroot(choose(131,14:29)) ,pch=19,col='red')
> plot( polyroot(choose(131,14:39)) ,pch=19,col='red')
> plot( polyroot(choose(131,14:59)) ,pch=19,col='red')
> plot( polyroot(choose(131,14:79)) ,pch=19,col='red')
> plot( polyroot(choose(131,14:99)) ,pch=19,col='red')
> plot( polyroot(choose(131,14:119)) ,pch=19,col='red')
> plot( polyroot(choose(131,14:139)) ,pch=19,col='red')










ratios and products of polynomials, exp, log, simple sums and differences of those. Code sketch here.

with Wegert, series and other terrible stuff becomes fun!










playing along with Elias Wegert in R:

X <- matrix(1:100,100,100)                  #grid
X <- X * complex(imaginary=.05) + t(X)/20    #twist & shout
X <- X - complex(real=2.5,imaginary=2.5)     #recentre
plot(X, col=hcl(h=55*Arg(sin(X)), c=Mod(sin(X))*40 ) ,        pch=46, cex=6)

Found it was useful to define these few functions:

arg <- function(z) (Arg(z)+pi)/2/pi*360     #for HCL colour input
ring <- function(C) C[.8 < Mod(C) &   Mod(C) < 1.2]        #focus on the unit circle
lev <- function(x) ceiling(log(x)) - log(x)
m <- function(z) lev(Mod(z))
plat <- function(domain, FUN) plot( domain, col= hcl( h=arg(FUN(domain)), l=70+m(domain)), pch=46, cex=1.5, main=substitute(FUN) )           #say it directly

NB, hcl's hue[0,360] so phase or arg needs to be matched to that.




























The Swift Luminescent Energy Drink of the Psyche, or, When Goorialla Whirls and Whorls and Roars

(por diproton)




Suppose you are an intellectual impostor with nothing to say, but with strong ambitions to succeed in academic life, collect a coterie of reverent disciples and have students around the world anoint your pages with respectful yellow highlighter. What kind of literary style would you cultivate?

Not a lucid one, surely, for clarity would expose your lack of content. The chances are that you would produce something like the following:

We can clearly see that there is no bi-univocal correspondence between linear signifying links or archi-writing, depending on the author, and this multireferential, multi-dimensional machinic catalysis. The symmetry of scale, the transversality, the pathic non-discursive character of their expansion: all these dimensions remove us from the logic of the excluded middle and reinforce us in our dismissal of the ontological binarism we criticised previously.

This is a quotation from the psychoanalyst Félix Guattari, one of many fashionable French ‘intellectuals’ outed….

scientist and polemicist Richard Dawkins, Postmodernism Disrobed. A review of Intellectual Impostures published in Nature 9 July 1998, vol. 394, pp. 141-143.

 

Above we read an assertion without evidence. Dawkins posits that an intellectual impostor with nothing to say would write in a certain way. But where’s the proof? I guess whoever’s reading this book review is assumed to already know what Dawkins (Sokal/Bricmont) are talking about and agree with his implications: namely, that postmodernists have nothing to say, and that they cultivate an obtuse literary style to obscure the fact (and that this somehow also attracts followers).

Who says “chances are”? Dawkins’ attack amounts to a flame.

 

Here is a not-unusual passage written in that other famously obtuse jargon, mathematics:

The prototypical example of a C*-algebra is the algebra B(H) of bounded (equivalently continuous) linear operators defined on a complex Hilbert space H; here x* denotes the adjoint operator of the operator x: H → H. In fact every C* algebra, A, is *-isomorphic to a norm-closed adjoint closed subalgebra of B(H)….

That’s from Wikipedia’s article on C* algebras. I think the language is similarly impenetrable to Guattari’s. But mathematics = science = good and humanities = not science = bad, at least in the minds of some.

Here is an excerpt (via @wtnelson) written for teachers of 4–12-year-olds, 40 years ago, by Zoltán Pál Dienes:

psychologically speaking, relating an object to another object is a very different matter from relating a set of objects to another set of objects. In the first case, perceptual judgment can be made on whether the relation holds or not in most cases, whereas in the case of sets, a certain amount of conceptual activity is necessary before such a judgment can take place. For example, we might need to count how many of a certain number of things there are in the set and how many of a certain number of these or of other things there are in another set before we can decide whether the first and the second sets are or are not related by a certain particular relation to each other.

Clear as mud! Clearly Z. P. Dienes was an intellectual impostor with ambitions to collect a coterie of reverent disciples.

 

I don’t know enough about postmodernism to opine on it. I just get annoyed when putatively sceptical people casually wave it off without proving their point.

(And if you’re going to point me to the Sokal Affair or Postmodernism Generator CGI, I’ll point you to At Whom Are We Laughing?.)

 

In Lacan: A Beginner’s Guide, Lionel Bailly describes his subject as “a thinker whose productions are sometimes irritatingly obscure”. He goes on:

Most Lacanian theory [comes from his]  spoken teachings…developed in discourse with…pupils…. [Various modes of presentation which are appropriate in speech] make frustrating reading. …leading the reader toward an idea, but never becoming absolutely explicit…difficult to discover what he actually said…thought on his feet—the ideas…in his seminars were never intended to be cast in stone…freely ascribes to common words new meanings within his theoretical model…Lacan, despite the fuzziness of his communication style, strove desperately hard for intellectual rigour….at the end of the day, it is … clinical relevance that validates Lacan’s model. [Lacan being a psychoanalyst and his ideas coming out of that work.]

So there’s an alternative hypothesis from an authority. Bailly admits the communication style was poor and gives reasons why it was. But rather than judging the work on rhetorical grounds, we should judge it on clinical merit—the ultimate empirical test!

Compare this to Dawkins. Besides the suppositions I already mentioned, he chooses words like: “intellectuals” within scare quotes; ‘anoint’, ‘revere’, ‘coterie’—to undermine the intellectual seriousness of his targets. Who are the empiricists here and who relies on rhetoric?

(Source: members.multimania.nl)




Consider ℂ, the field of complex numbers, as a 1-dimensional vector space. The balanced sets are ℂ itself, the empty set and the open and closed discs centered at 0 (visualizing complex numbers as points in the plane). Contrariwise, in the two dimensional Euclidean space there are many more balanced sets: any line segment with midpoint at (0,0) will do.

As a result, ℂ and ℝ² are entirely different as far as their vector space structure is concerned.

(Source: Wikipedia)




A road map of mathematical objects by Max Tegmark, via intothecontinuum:

The arrows generally indicate addition of new symbols and/or axioms. Arrows that meet indicate the combination of structures.
For instance, an algebra is a vector space that is also a ring, and a Lie group is a group that is also a manifold.

A road map of mathematical objects by Max Tegmark, via intothecontinuum:

The arrows generally indicate addition of new symbols and/or axioms. Arrows that meet indicate the combination of structures.

For instance, an algebra is a vector space that is also a ring, and a Lie group is a group that is also a manifold.


hi-res




Just playing with z² / z² + 2z + 2

g(z)=\frac{z^2}{z^2+2z+2}

on WolframAlpha. That’s Wikipedia’s example of a function with two poles (= two singularities = two infinities). Notice how “boring” line-only pictures are compared to the the 3-D ℂ→>ℝ picture of the mapping (the one with the poles=holes). That’s why mathematicians say ℂ uncovers more of “what’s really going on”.

As opposed to normal differentiability, ℂ-differentiability of a function implies:

  • infinite descent into derivatives is possible (no chain of C¹ ⊂ C² ⊂ C³ ... Cω like usual)

  • nice Green’s-theorem type shortcuts make many, many ways of doing something equivalent. (So you can take a complicated real-world situation and validly do easy computations to understand it, because a squibbledy path computes the same as a straight path.)
  

Pretty interesting to just change things around and see how the parts work.

  • The roots of the denominator are 1+i and 1−i (of course the conjugate of a root is always a root since i and −i are indistinguishable)
  • you can see how the denominator twists
  • a fraction in ℂ space maps lines to circles, because lines and circles are turned inside out (they are just flips of each other: see also projective geometry)
  • if you change the z^2/ to a z/ or a 1/ you can see that.
  • then the Wikipedia picture shows the poles (infinities) 

Complex ℂ→ℂ maps can be split into four parts: the input “real”⊎”imaginary”, and the output “real"⊎"imaginary”. Of course splitting them up like that hides the holistic truth of what’s going on, which comes from the perspective of a “twisted” plane where the elements z are mod z • exp(i • arg z).

a conformal map (angle-preserving map)

ℂ→ℂ mappings mess with my head…and I like it.