# Eikonal Blog

## 2010.07.28

### Security tools

2011.02.28: This post was getting too large, so I broke it into smaller pieces:

There are still some smaller islands of content that do not yet deserve separate postings:

• GFI Languard
• NSS
• Lumension
• EndPoint

Sites:

## Misc

Sources:

### Version control systems

Filed under: tools — Tags: , , , , — sandokan65 @ 10:25

## 2010.07.22

### Scripting user interfaces

Filed under: web tools — Tags: , , , , , — sandokan65 @ 13:32

Browser scripting:

### Volume of the ball

Filed under: geometry — Tags: , — sandokan65 @ 13:12
• The “volume” $\Omega_n :\equiv \hbox{Vol}(B^n)$ of the ball $B^n :\equiv \{x \in {\Bbb R}^n | s/t |x|<1\}$ is given by $\Omega_n = \frac{\pi^{n/2}}{\Gamma(1+\frac{n}2)}$.
• The “surface area” $\omega_n :\equiv \hbox{Area}({\Bbb S}^{n-1})$ of the sphere ${\Bbb S}^{n-1} :\equiv \{x \in {\Bbb R}^n | s/t |x|=1\} = \partial B^n$ is given by $\omega_n = (n+1) \Omega_{n+1}$.

Note: $\Omega_{n+2} = \frac{\pi}{n+1}\Omega_n$, so: $\Omega_{2n} = \frac{\pi^n}{(2n-1)!!}$ and $\Omega_{2n+1} = \frac{8 \pi^n}{3(2n)!!}$.

Examples:
$\begin{array}{ | c | c | c | c | c | c | c | c |} \hline n & 2 & 3 & 4 & 5 & 6 & 7 & 8 \\ \hline \Omega_n & \pi & \frac{4\pi}{3} & \frac{\pi^2}2 & \frac{\pi^2}3 & \frac{\pi^3}{10} & \frac{\pi^3}{18} & \frac{\pi^4}{70} \\ \hline \omega_{n-1} & 2\pi & 4\pi & 2\pi^2 & \frac{5\pi^2}{3} & \frac{3\pi^3}5 & \frac{7\pi^3}{18} & \frac{4\pi^4}{35} \\ \hline \end{array}$

Alzer’s inequalities (as cited in [1]):

• $a \Omega_{n+1}^{\frac{n}{n+1}} \le \Omega_n \le b \Omega_{n+1}^{\frac{n}{n+1}}$, where $a=\frac{2}{\sqrt{2}} = 1.128,37\cdots$, $b=\sqrt{e}=1.648,72\cdots$;
• $\sqrt{\frac{n+A}{2\pi}} \le \frac{\Omega_{n-1}}{\Omega_n} \le \sqrt{\frac{n+B}{2\pi}}$, where $A=\frac12$ and $B=\frac\pi2-1=0.570,79\cdots$;
• $\left(1+\frac1{n}\right)^\alpha \le \frac{\Omega_n^2}{\Omega_{n-1}\Omega_{n+1}} \le \left(1+\frac1{n}\right)^\beta$, where $\alpha=2-\frac{\ln(\pi)}{\ln(2)} = 0.348,50\cdots$ and $\beta=\frac12$.

Sources:

1. [1] “Topics in Special Functions” by G. D. Anderson, M. K. Vamanamurthy, M. Vuorinen – http://arxiv.org/abs/0712.3856

### Library of metrics

Filed under: General relativity, geometry — Tags: , , — sandokan65 @ 09:42

In $D=1+3$ dimensions the ADM (Arnowitt-Deser-Misner) split of the metric is given by ($i,j\in\overline{1,3}$, $\mu,\nu\in\overline{0,3}$):

$ds^2 = -N^2 dt^2 + g_{ij}^{(3)}(dx^i+N^i dt)(dx^j+N^j dt)$
where $N$ is the lapse variable, $N^i$ is the shift 3-vector.

Here:

• $R = K_{ij}K^{ij} - K^2 + R^{(3)} + 2\nabla_\mu (n^\mu \nabla_\nu n^\nu - n^\nu \nabla_\nu n^\mu)$ is the Ricci scalar,
• $K_{ij} :\equiv \frac1{2N} (\dot{g}_{ij}^{(3)} - \nabla_i^{(3)} N_j - \nabla_j^{(3)} N_i)$ is the extrinsic curvature, $K :\equiv g^{ij}K_{ij}$.

Source: “Unifying inflation with dark energy in modified F(R) Horava-Lifshitz gravity” by E. Elizalde, S. Nojiri, S. D. Odintsov, D. Saez-Gomez; arXiv.org > hep-th > arXiv:1006.3387 (http://arxiv4.library.cornell.edu/abs/1006.3387).

More:

## 2010.07.20

### Vector bases for 3D kinematics

Filed under: mathematics — Tags: — sandokan65 @ 16:02

## Relevant sets of basis vectors

There are four relevant sets of orthonormal basis vectors (=triads) here:

• ${\cal B}_1 :\equiv \{\underline{e}_x,\underline{e}_y,\underline{e}_x\}$ – orts corresponding to the Cartesian coordinates $\{x,y,z\}$,
• ${\cal B}_3 :\equiv \{\underline{n},\underline{p},\underline{q}\}$, defined by:
• $\underline{n} :\equiv \frac1{r}\underline{r} = (\cos(\theta)\cos(\varphi),\cos(\theta)\sin(\varphi),\sin(\theta)) ,$
• $\underline{p} :\equiv \frac{\partial}{\partial \theta} \underline{n} = (-\sin(\theta)\cos(\varphi),-\sin(\theta)\sin(\phi),\cos(\theta)),$
• $\underline{q} :\equiv \frac1{\cos(\theta)}\frac{\partial}{\partial \varphi} \underline{n} = (-\sin(\varphi),\cos(\phi),0),$

Note that here: $\underline{n}\times\underline{p} = - \underline{q}$, ie. that this basis is left-handed.

• ${\cal B}_3 :\equiv \{\underline{n},\underline{m},\underline{k}\}$ – radius-based basis, defined by:
• $\underline{n} :\equiv \frac1{r}\underline{r},$
• $\underline{m} :\equiv \hbox{Normalized}(\underline{n}')$,
• $\underline{k} :\equiv \underline{n}\times\underline{m}$.
• ${\cal B}_4 :\equiv \{\underline{T},\underline{O},\underline{B}\}$ – tangent-based basis (“frame”), defined by:
• $\underline{T} :\equiv \hbox{Normalized}(\underline{r}') = \frac1{v}\underline{v} = \frac{r'}{v} \underline{n} + \frac{r \Phi'}{v} \underline{m}$,
• $\underline{N} :\equiv \hbox{Normalized}(\underline{T}')$
• $\underline{B} :\equiv \underline{T}\times\underline{N}$.

where $\underline{v} :\equiv \underline{r}' = r' \underline{n} + r \Phi' \underline{m}$ and $v(t) = \sqrt{r'^2+r^2\Phi'^2}$.
Note that $\underline{N} \ne \underline{n}$.

${\cal B}_2$:

• $\underline{n}' = \theta' \underline{p} + \cos(\theta)\varphi' \underline{q}$,
• $\underline{p}' = -\theta' \underline{n} - \sin(\theta)\varphi' \underline{q}$,
• $\underline{q}' = -\cos(\theta) \theta' \underline{n} + \sin(\theta)\varphi' \underline{p}$.

${\cal B}_3$:

• $\underline{n}' = \Phi' \underline{m}$,
• $\underline{m}' = -\Phi' \underline{n} + \Theta' \underline{k}$,
• $\underline{k}' = -\Theta' \underline{m}$.

Note that $\Phi$ and $\Theta$ are not the same as $\varphi$ and $\theta$. They are defined by these equations.

A vector $\underline{A} = A_n\underline{n}+A_m\underline{m}+A_k\underline{k}$ evolves according to:
$\underline{A}' = [A'_n - \Phi' A_m]\underline{n} + [A'_m + \Phi' A_n - \Theta' A_k]\underline{m} + [A'_k + \Theta' A_m]\underline{k}$.

${\cal B}_4$ is guided by the Frenet–Serret formulas:

• $\frac{d}{ds}\underline{T} = \kappa \underline{N}$,
• $\frac{d}{ds}\underline{N} = -\kappa \underline{T} + \tau \underline{B}$,
• $\frac{d}{ds}\underline{B} = -\tau \underline{N}$.

where $s(t) :\equiv \int_0^t dt' v(t')$.

${\cal B}_3$ in terms of ${\cal B}_2$:

• $\underline{n} = \underline{n}$,
• $\underline{p} = \frac{\theta'}{\Phi'} \underline{m} + \cos(\theta)\frac{\varphi'}{\Phi'} \underline{k}$,
• $\underline{q} = \cos(\theta) \frac{\varphi'}{\Phi'} \underline{m} - \frac{\theta'}{\Phi'} \underline{k}$.

${\cal B}_2$ in terms of ${\cal B}_3$:

• $\underline{n} = \underline{n}$,
• $\underline{m} = \frac{\theta'}{\Phi'} \underline{p} + \cos(\theta)\frac{\varphi'}{\Phi'} \underline{q}$,
• $\underline{k} = \cos(\theta) \frac{\varphi'}{\Phi'} \underline{p} - \frac{\theta'}{\Phi'} \underline{q}$.

Note: Here

• $\Phi'^2 :\equiv \theta'^2 + \cos(\theta)^2 \varphi'^2$,
• $\Theta' :\equiv \sin(\theta) \varphi' \left(1+\frac{\theta'^2}{\Phi'^2}\right) + \cos(\theta) \frac{\theta''\varphi'-\theta'\varphi''}{\Phi'^2}$.

Note: if we replace $t$ with $\Phi$, then

• $\left(\frac{d\theta}{d\Phi}\right)^2 + \cos(\theta)^2 \left(\frac{d\varphi}{d\Phi}\right)^2=1$,
• $\frac{d\Theta}{d\Phi} = \sin(\theta) \left(\frac{d\varphi}{d\Phi}\right) \left[1+\left(\frac{d\theta}{d\Phi}\right)^2\right] + \cos(\theta) \left[\frac{d^2\theta}{d\Phi^2}\frac{d\varphi}{d\Phi}-\frac{d\theta}{d\Phi}\frac{d^2\varphi}{d\Phi'^2}\right]$.

Related:

### Conservative motion of a 3D particle in potential-like force fields

Filed under: Uncategorized — Tags: , — sandokan65 @ 09:20

Let’s consider the right-hand oriented orthonormal triad ${\cal B} :\equiv \{\underline{n},\underline{m},\underline{k}\}$ ($\underline{n}\cdot\underline{m}= \underline{n}\cdot\underline{k} = \underline{m}\cdot\underline{k}= 0$ and $\underline{n}^2 = \underline{m}^2 = \underline{k}^2 = 1$) assigned to a curve $c$ in 3-dimensional Euclidean space ${\Bbb R}^3$. Let this curve be parametrized by the “time” parameter $t$ associated to the “current” position $\underline{r}(t)$ of a particle moving along that curve. Instead of defining the triad ${\cal T}$ as a tangential vectors (i.e. the tangential, normal and bi-normal vectors) to the $c$ at $\underline{r}$, define it based on the radius vector $\underline{r}$ by $\underline{r} \equiv: \underline{n} r$.

The triad vectors satisfy following evolution equations:

• $\underline{n}' \equiv: \varphi' \underline{m}$,
• $\underline{m}' \equiv: - \varphi' \underline{n} + \theta' \underline{k}$,
• $\underline{k}' = -\theta' \underline{m}$,

where $\phi(t)$ and $\theta(t)$ are two angles defining the position of the particle.

In following we will look at the several choices for the force field $\underline{F}$ that guides the motion of the particle via Newton’s equation $\underline{r}'' = \underline{F}(\underline{r}, \underline{r}')$.

## The simplest case

For $\underline{r}'' = f(r) \underline{r}$ one finds:

• $r'' = f(r) r + \frac{l^2}{r^3}$ (radial equation of motion),
• $r^2\phi' = l (= const|_{t})$ (preservation of angular momentum),
• $\theta' \equiv 0$ (i.e. the trajectory is planar).

## A simple generalization

In force field $\underline{F} = f(r) \underline{r} + g(r) \underline{r}'$ one finds:

• $r'' = f(r) r + g(r) r' + r \varphi'^2$ (radial equation of motion),
• $l(t) :\equiv r^2\phi'$ (definition of non-constant angular momentum),
• $l' = g(r) l$ (equation guiding the evolution of the angular momentum),
• $\theta' \equiv 0$, i.e. the trajectory is (still) planar.

This system can be somehow simplified by use of $\varphi$ instead of $t$, and by introduction of the Binet variable $u(\varphi) :\equiv \frac1{r(t)}$:

• $- \frac{d^2 u}{d\varphi^2} = u + \frac{f[u]}{l^2 u^3}$
• $\frac{d l}{d\varphi} = \frac{g[u]}{u^2}$.

with $f[u] :\equiv f(r)$, $g[u] :\equiv g(r)$, $\frac{d}{dt} = l u^2 \frac{d}{d\varphi}$, $r'(t) = - l \frac{d u}{d\varphi}$ and $r''(t) = - l u^2 \frac{d}{d\varphi}\left(l \frac{d u}{d\varphi}\right)$.

## Further generalization

For $\underline{r}'' = f(r) \underline{r} + g(r) \underline{r}' + h(r) \underline{r}\times\underline{r}'$ we get:

• $r'' = f r + g r' + r \varphi'^2$,
• $l :\equiv r^2 \varphi'$,
• $l' = g(r) l$,
• $\theta' = h(r) r$ – the trajectory is not planar any more.

which, in Binet coordinates has following form

• $- \frac{d^2 u}{d\varphi^2} = u + \frac{f[u]}{l^2 u^3}$
• $\frac{d l}{d\varphi} = \frac{g[u]}{u^2}$.
• $\frac{d \theta}{d\varphi} = \frac{h[u]}{l u^3}$.

## 2010.07.19

### Windows command line shortcuts

Filed under: windows — Tags: — sandokan65 @ 23:42
• Default registry editor: regedit
• Windows Installer:
• Correcting the occasional problem with registration of MSI file type:
• 1) first run: msiexec /unregister;
• 2) then run: msiexec /regserver
• Correcting the situation where the Windows Installer does not run properly but refuses to reinstall (source: http://support.microsoft.com/default.aspx?scid=KB;EN-US;319624):

Method 5: Fix the broken security key for the MsiServer service

• 1. Start the computer by using Windows 2000.
• 2. Click Start, click Run, type regedit.exe, and then rename the following key to Old_Security:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSIServer\Security
• 3.. Restart the computer (you must do this).
• 4. Run Instmsiw.exe for installer 2.0 again; this corrects the broken security key for the MSI service.

• Installing a MSI file using the command line version of Windows installer: msiexec /i python-2.6.5.msi
• Accessing the Services applet: services.msc
• Killing multiple instances of a process: taskkill /IM “outlook.exe” /f (Source: http://anigan.wordpress.com/2008/03/26/using-taskkill-to-kill-muliple-instances-of-outlookexe/)
• Windows protected file cheker: sfc

## 2010.07.16

### Paywalls

Filed under: opression, paywalls — Tags: — sandokan65 @ 12:27
• Murdoch’s UK Paywall a Miserable Failure (SlashDot; 2010.07.16) – http://news.slashdot.org/article.pl?sid=10/07/16/027236
“As part of his war against free, Rupert Murdoch put the Times and Sunday Times of London behind a paywall. Michael Wolff of Newser asks how that’s working out for him. You can guess: miserable failure: ‘Not only is nobody subscribing to the website, but subscribers to the paper itself — who have free access to the site — are not going beyond the registration page. It’s an empty world.’ Not that this wasn’t entirely predictable.”
• What’s Really Going on Behind Murdoch’s Paywall? by Michael Wolf (newser; 2010.07.14) – http://www.newser.com/off-the-grid/post/502/whats-really-going-on-behind-murdochs-paywall.html
• The Times Erects a Paywall, Plays Double Or Quits (SlashDot; 2010.03.27) – http://news.slashdot.org/story/10/03/27/0356211/The-Times-Erects-a-Paywall-Plays-Double-Or-Quits
“News International, owners of The Times and The Sunday Times announced today that from June readers will be required to pay £1 per day or £2 per week to access content. Rupert Murdoch is delivering on his threat to make readers pay, and is trying out this experiment with the most important titles in his portfolio. No one knows if this will work — there is no consensus on whether it is a good or bad thing for the industry, but be very clear that if it succeeds every one of his competitors will follow. Murdoch has the luxury of a deep and wide business, so he can push this harder than any company that has to rely upon one or two titles for revenue.”
• Newsday Gets 35 Subscriptions To Pay Web Site (SlashDot; 2010.01.27) – http://news.slashdot.org/story/10/01/27/1345219/Newsday-Gets-35-Subscriptions-To-Pay-Web-Site

## 2010.07.13

Filed under: TeX — Tags: , , , , , , , , , , — sandokan65 @ 16:03

## (to be a) Cheatsheet

### Lists

 \begin{list}{label code}{body code} \item Item one \item Item two \item Item three \end{list} 

Example:

 \begin{list}{*}{} \item Item one \item Item two \item Item three \end{list} 

### Error: “extra alignment tab has been changed to \cr” in pmatrix environment

Trying to compile the matrix with 16 columns:

 $$\begin{pmatrix} 1&0&0&0& 0&0&0&0& 0&1&0&0& 0&0&0&0 \\ 0&0&0&0& 1&0&0&0& 0&0&0&0& 0&1&0&0 \\ 0&0&1&0& 0&0&0&0& 0&0&0&1& 0&0&0&0 \\ 0&0&0&0& 0&0&1&0& 0&0&0&0& 0&0&0&1 \end{pmatrix}$$ 

produced following error:

 ./document.tex:750: Extra alignment tab has been changed to \cr. \endtemplate l.750 1&0&0&0& 0&0&0&0& 0&1& 0&0& 0&0&0&0 \\ 

It appears that LaTeX has some internal limitation on default maximal number of columns. This can be changed (accoring to http://newsgroups.derkeiler.com/Archive/Comp/comp.text.tex/2006-06/msg01298.html) by setting

 \setcounter{MaxMatrixCols}{16} 

in the preamble of the document.

### Diferentiating primes

Filed under: mathematics — Tags: , — sandokan65 @ 15:50

Source:

• How to Differentiate a Number; by Victor Ufnarovski and Bo Ahlander; Journal of Integer Sequences, Vol 6 (2003), Article 0334
• T24661

Definition: On the set of integer numbers ${\Bbb N}_0=\{0,1,2,\cdots\}$ introduce following unary operation:

• $0' = 0,$
• $1' = 0,$
• $p' = 1, \ \ \ (\forall p \in {\Bbb P}),$
• $(ab)' = a'b+a b' \ \ \ \ (\forall a, b \in {\Bbb N}) \ \ (\hbox{Leibnitz rule}).$

Examples:
$\begin{tabular}{ | c | c c c c c c c c c c c c c c c c c c |} \hline n & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 10 & 11 & 12 & 13 & 14 & 15 & 16 & 17 & 18 \\ \hline n' & 0 & 1 & 1 & 4 & 1 & 5 & 1 & 12 & 6 & 7 & 1 & 16 & 1 & 9 & 8 & 32 & 1 & 81 \\ \hline n'' & 0 & 0 & 0 & 4 & 0 & 1 & 0 & 16 & 5 & 1 & 0 & 32 & 0 & 6 & 12 & 80 & 0 & 10 \\ \hline n''' & 0 & 0 & 0 & 4 & 0 & 0 & 0 & 32 & 1 & 0 & 0 & 80 & 0 & 5 & 16 & 176 & 0 & 7 \\ \hline n'''' & 0 & 0 & 0 & 4 & 0 & 0 & 0 & 80 & 0 & 0 & 0 & 176 & 0 & 0 & 32 & 368 & 0 & 0 \\ \hline \end{tabular}$

Note:

• $(a+b)' \ne a' + b',$
• $(a b)'' \ne a''b+2a'b'+a b''.$

Examples:

• $(2k)' = k + 2 k' \ge 2k',$
• $(3k)' = k+3k' \ge 3k',$
• $(4k)' = 4k + 4k' \ge 4k',$
• $(5k)' = k + 5k' \le (2k)' + (3k)'.$

Note: The only pairs $(a,b)$ s/t $a\le b \le 100$ with $gcd(a,b)=1$ and $(a+b)'=a'+b'$ are:
$\{(1,2), (4,35), (4, 91), (8, 85), (11,11), (18, 67), (26,29), (27, 55), (35, 55), (36, 81), (38, 47), (38, 83), (50, 79), (62, 83), (95,99)\}$.

Theorem: $n'\ge n \Rightarrow (kn)' \ge kn, \ \ \ \ (\forall k > 1).$

Theorem: If $n = \prod_{i=1}^k {p_i}^{n_i}$ then $n' = n \sum_{i=1}^{k} \frac{n_i}{p_i}.$

Theorem: For $n = m p^p$, ($p\in {\Bbb P}$, $m> 1, \in {\Bbb N}$)

• $n' = p^p (m+m'),$
• $\lim_{k\rightarrow \infty} n^{(k)} = \infty.$

## Extensions:

One can extend the differentiation operation to wider sets of numbers. For example, by setting $(-1)’=0$ one gets extension to the whole set of integer numbers ${\Bbb Z}$:

• $(-1)' = 0,$,
• $(-p)' = -1, \ \ \ (\forall p \in {\Bbb P})$,
• $(-x)' = - x', \ \ \ (\forall x \in {\Bbb Z})$.

One can also infer that:

• $i' = 0,$
• $\omega' = 0, \ \ \ (\forall \omega^m = 1, \ \ m\in {\Bbb N}),$
• $\omega' = 0, \ \ \ (\forall \omega^\alpha = 1, \ \ \alpha\in {\Bbb C}\ \{0\}).$
• $\left(\sqrt{p}\right)' = \frac{\sqrt{p}}{2p},$
• $\left(\frac1{p}\right)' = -\frac{1}{p^2},$
• $\left(p^\alpha\right)' = -\alpha p^{\alpha-1},$
• $\ln(p)' = \frac1{p},$
• $\left(\frac{n}{m}\right)' = \frac{n'm- n m'}{m^2}.$

Definition:

• $\pi(n) :\equiv \ (\# \ of \ p \le n),$
• $\pi_1(n) :\equiv \pi(n) - \pi(n-1).$

Lemma:

• $\pi_1(n) = 1$ if $n=p,$
• $\pi_1(n) = 0$ if $n\ne p.$

Lemma:

• $\pi_1(n) = 1 \Leftrightarrow n'=1,$
• $\pi_1(n) = 0 \Leftrightarrow n'\ne 1.$

### Stages of checking password crackability

1. Check if password is empty.
3. For system (or application) provided accounts, use the Google to find default passwords provided by manufacturers’, and test them against these accounts on your system(s).
4. Check if password is in the custom assembled corporate dictionary.
5. Check if password is in the selected language’s dictionary. (see: https://eikonal.wordpress.com/2010/03/29/default-passwords/)
6. Check if password is a dictionary word + one digit.
7. Check if password is an 311tized word.
8. Is password the concatenation of multiple words.
9. Check in the database of precomputed password hashes.
10. Desperate measure: brute force cracking.

### Time inversion

Filed under: qft — Tags: , , — sandokan65 @ 14:02

Time inversion

• ${\cal T} = {\cal U}{\cal K}$
• $\hat{x}:\equiv (-x^0,\vec{x}) = -\bar{x}$
• ${\cal T}H{\cal T}^{-1} = H$
• ${\cal T}{\cal L}(x){\cal T}^{-1} = {\cal L}(\hat{x})$
• ${\cal T}j_\mu(x){\cal T}^{-1} = j^\mu(\hat{x})$

## Scalar field – real

• ${\cal T}\phi(x){\cal T}^{-1} = \epsilon\phi(\hat{x})$
• ${\cal T}a(\vec{k}){\cal T}^{-1} = \epsilon a(-\vec{k})$
• ${\cal T}a^\dagger(\vec{k}){\cal T}^{-1} = \epsilon a^\dagger(-\vec{k})$
• ${\cal U}a(\vec{k}){\cal U}^{-1} = \epsilon a^\dagger(-\vec{k})$
• ${\cal U}a^\dagger(\vec{k}){\cal U}^{-1} = \epsilon a(-\vec{k})$

where $\epsilon=\pm 1$.

So:
${\cal U} = e^{-\frac{i\pi}2 \int d^3\vec{k} (a^\dagger(\vec{k})a(\vec{k}) - \epsilon a^\dagger(\vec{k})a(-\vec{k}))}.$

## Scalar field – complex

${\cal T}\phi(x){\cal T}^{-1} = \epsilon\phi^{*}(\hat{x})$

## Dirac field

Here:

• ${\cal T}\psi(x){\cal T}^{-1} = T \psi(\hat{x})$
• ${\cal T}\bar{\psi}(x){\cal T}^{-1} = \bar{\psi}(\hat{x}) \gamma^0 T^\dagger \gamma^0,$

where

• $T :\equiv i\gamma^1 \gamma^3 = T^\dagger = T^{-1} = - T^{*},$
• $T \gamma_\mu T^{-1} = \gamma_\mu^T = \gamma^{\mu \ *}.$

Then

• $T u(p,s) = u^*(-p,-s)e^{i\alpha_+(p,s)},$
• $T v(p,s) = v^*(-p,-s)e^{i\alpha_-(p,s)},$

\ni where $\alpha_\pm(p,s) = \pi + \alpha_\pm(-p,-s)$.

Now

• ${\cal U} b(p,s) {\cal U}^{-1} = -b(-p,-s) e^{i\alpha_+(p,s)},$
• ${\cal U} d^\dagger(p,s) {\cal U}^{-1} = -d^\dagger(-p,-s) e^{i\alpha_-(p,s)}.$

Split ${\cal U} = {\cal U}_1{\cal U}_2$ s/t

• ${\cal U}_1 b(p,s) {\cal U}_1^{-1} = e^{i\alpha_+(p,s)} b(p,s),$
• ${\cal U}_1 d^\dagger(p,s) {\cal U}_1^{-1} = e^{i\alpha_-(p,s)} d^\dagger(p,s),$
• ${\cal U}_2 b(p,s) {\cal U}_2^{-1} = -b(-p,-s),$
• ${\cal U}_2 d^\dagger(p,s) {\cal U}_2^{-1} = -d^\dagger(-p,-s).$

Their realizations are:

• ${\cal U}_1 = e^{- i \int d^3\vec{p} \sum_s (\alpha_+(p,s) b^\dagger(p,s)b(p,s) - \alpha_(p,s)d^\dagger(p,s)d(p,s))},$
• ${\cal U}_2 = e^{- i \frac{\pi}2 \int d^3\vec{p} \sum_s (b^\dagger(p,s)b(p,s) + b^\dagger(p,s)b(-p,-s) - d^\dagger(p,s)d(p,s) - d^\dagger(p,s)d(-p,-s))}.$

## Electromagnetic field

• ${\cal T}A^\mu(x){\cal T}^{-1} = A_\mu(\hat{x}),$
• ${\cal U}\vec{a}^a(\vec{k}){\cal U}^{-1} = - (-)^a a^a(-\vec{k}),$
• ${\cal U} = e^{\frac{i\pi}2 \int d^3k (a^\dagger(\vec{k})^a a(\vec{k})_a + (-)^a a^\dagger(\vec{k})^a a(-\vec{k})_a}$.

### Chord and Scale Pattern Generator

Filed under: music — Tags: , — sandokan65 @ 13:42

Source: I have lost the reference to the original source.

 #! /bin/bash # Allen Barker # Sept. 17, 2004 # Chord and Scale Pattern Generator, Version 0.1. # This is "human rights ware," copyright (C) Allen Barker, 2004. # It can be freely copied and modified as long as the human # rights message remains. If you distribute modified copies, # please document somewhere in the code, etc., that you have # modified it. (Yes, the code is ugly, but at least it works!) numColumns="77" # rounded down to the nearest factor of 4 plus 1 numRows="50" # rounded down to the nearest factor of 4 plus 1 nonMarkedChar=" " function isMarked() { # Usage: isMarked # Outputs "true" if note is in markedNotes, "false" otherwise. for i in $markedNotes do if [ "$1" == "$i" ] ; then echo "true" return fi done echo "false" return } function addNotesMod12() { # Usage: addNotesMod12 note1=$1 note2=$2 if [ "$note1" == "a" ]; then (( note1=10 )); fi if [ "$note1" == "b" ]; then (( note1=11 )); fi if [ "$note2" == "a" ]; then (( note2=10 )); fi if [ "$note2" == "b" ]; then (( note2=11 )); fi (( sum = note1 + note2 )) if (( sum > 11 )); then (( sum -= 12 )); fi if (( sum == 10 )); then sum="a"; fi if (( sum == 11 )); then sum="b"; fi echo$sum } function transposeList() { # Usage: transposeList # Adds the delta factor to all the notes on the list and returns # the transposed list via echo. delta=$1 newList="" shift for i in$* do newList="$newList addNotesMod12$delta $i" done echo$newList } function printRow() { # Usage: printRow markedCols="" markedDiagCols1="" markedDiagCols2="" markedDiagCols3="" (( colCount = 1 )) while true do for note in $1$2 $3 do if [ "isMarked$note" == "true" ]; then # see if the previous note was marked... prevNote=addNotesMod12 $note 8 if [ "isMarked$prevNote" == "true" ]; then if (( colCount > 1 )); then echo -n "---" fi else if (( colCount > 1 )); then echo -n "$nonMarkedChar$nonMarkedChar$nonMarkedChar" fi fi # mark the columns for later... belowNote=addNotesMod12$note 9 if [ "isMarked $belowNote" == "true" ]; then markedCols="$markedCols $colCount" fi belowLeft=addNotesMod12$note 5 if [ "isMarked $belowLeft" == "true" ]; then (( tmpCol = colCount-1 )) markedDiagCols1="$markedDiagCols1 $tmpCol" (( tmpCol = colCount-2 )) markedDiagCols2="$markedDiagCols2 $tmpCol" (( tmpCol = colCount-3 )) markedDiagCols3="$markedDiagCols3 $tmpCol" fi else # not a marked note if (( colCount > 1 )); then echo -n "$nonMarkedChar$nonMarkedChar$nonMarkedChar" fi fi (( colCount=colCount+4 )) echo -n $note if (( colCount > numColumns )) ; then echo -n " " # this space is needed to make the sub to standard notes work echo return fi done done } function printBetweenRows() { # Usage: printBetweenRows # Uses the global column-marking lists. for betweenRow in 1 2 3 do (( colCount = 1 )) (( mod4Count = 0 )) while true do if (( colCount > numColumns )) ; then echo break fi printedChar="false" # loop to test if current column is marked for colTest in$markedCols do if (( colCount == colTest )) ; then echo -n "|" printedChar="true" fi done if [ "$betweenRow" == "1" ]; then markedDiagCols="$markedDiagCols1" elif [ "$betweenRow" == "2" ]; then markedDiagCols="$markedDiagCols2" else # betweenRow ==3 markedDiagCols="$markedDiagCols3" fi for colTest in$markedDiagCols do if (( colCount == colTest )) ; then echo -n "/" printedChar="true" fi done # print the usual symbol if no marked char printed if [ "$printedChar" == "false" ]; then if (( mod4Count == 0 )); then echo -n "$nonMarkedChar" elif (( mod4Count == 1 )); then if [ "$betweenRow" == "3" ]; then echo -n "$nonMarkedChar" else echo -n " " fi elif (( mod4Count == 2 )); then if [ "$betweenRow" == "2" ]; then echo -n "$nonMarkedChar" else echo -n " " fi elif (( mod4Count == 3 )); then if [ "$betweenRow" == "1" ]; then echo -n "$nonMarkedChar" else echo -n " " fi fi fi (( colCount=colCount+1 )) (( mod4Count=mod4Count+1 )) if (( mod4Count == 4 )); then (( mod4Count = 0 )); fi done done } #============================= Start Main Menu ============================ echo echo echo "-----------------------------------------------------------------------" echo "Welcome to the chord and scale pattern generator, by Allen Barker, 2004." echo "All notes are represented in base 12 for entry and default display," echo "but can be converted to standard note representations. The (arbitrary)" echo "convention is: 0=B 1=C 2=C# 3=D 4=D# 5=E 6=F 7=F# 8=G 9=G# a=A b=A#." echo "Any yes/no menu choices default to \"n\" if nothing is entered." echo "-----------------------------------------------------------------------" echo "|\/\/\/\/\/\/\/\/\/\/\ Demand Human Rights! /\/\/\/\/\/\/\/\/\/\/\/\/\|" echo "-----------------------------------------------------------------------" echo echo echo "All preset patterns assume a root or key of 0, which can be" echo "transposed. Any user-entered note collections will also be transposed." echo "(I.e., the transposition factor is added to all the notes mod 12;" echo "transposing *down* by x is the same as transposing up by 12-x.)" echo echo "What root note/key to transpose to (where 0 = no transposition)?" echo -n "Please enter a base 12 digit: [0123456789ab] " read rootNote if [ "$rootNote" == "" ]; then rootNote="0"; fi echo echo "What collection of notes would you like highlighted links between?" echo " 1) major scale" echo " 2) natural minor scale" echo " 3) some mode of the major scale" echo " 4) pentatonic minor scale" echo " 5) pentatonic major scale" echo " 6) harmonic minor scale" echo " 7) melodic minor scale" echo " 8) all notes, chromatic scale" echo " 9) other, user-specified" echo -n "Enter a choice: [1-6] " read noteSet if [ "$noteSet" == "" ]; then noteSet="9"; fi if [ "$noteSet" = 1 ]; then markedNotes="2 5 9 0 4 7 b" elif [ "$noteSet" = 2 ]; then markedNotes="5 8 0 3 7 a 2" elif [ "$noteSet" = 3 ]; then echo echo " Ionian = major scale; Aeolian = natural minor scale" echo echo " Scale name Root, relative to a major scale in key 0" echo " 1) Ionian 0" echo " 2) Dorian 2" echo " 3) Phrygian 4" echo " 4) Lydian 5" echo " 5) Mixolydian 7" echo " 6) Aeolian 9" echo " 7) Locrian b" echo echo -n " Enter the number 1-7 corresponding to the mode: " read modeName if [ "$modeName" == "" ]; then modeName="1"; fi if [ "$modeName" = 1 ]; then modeOffset="0" elif [ "$modeName" = 2 ]; then modeOffset="a" elif [ "$modeName" = 3 ]; then modeOffset="8" elif [ "$modeName" = 4 ]; then modeOffset="7" elif [ "$modeName" = 5 ]; then modeOffset="5" elif [ "$modeName" = 6 ]; then modeOffset="3" elif [ "$modeName" = 7 ]; then modeOffset="1" fi markedNotes="2 5 9 0 4 7 b" markedNotes="transposeList$modeOffset $markedNotes" elif [ "$noteSet" = 4 ]; then markedNotes="0 3 5 7 a" elif [ "$noteSet" = 5 ]; then markedNotes="0 2 4 7 9" elif [ "$noteSet" = 6 ]; then markedNotes="2 5 8 0 b 3 7" elif [ "$noteSet" = 7 ]; then markedNotes="0 2 3 5 7 9 b" elif [ "$noteSet" = 8 ]; then markedNotes="0 1 2 3 4 5 6 7 8 9 a b" elif [ "$noteSet" = 9 ]; then echo echo " Please enter a list of notes from 0 to b, separated by spaces." echo " (Be sure to use a and b for base 12 versions of 10 and 11.)" echo -n " Notes as base 12 digits: " read markedNotes if [ "$markedNotes" == "" ]; then markedNotes="0"; fi fi echo echo -n "Do you want a chord diagram printed after the table [yn]? " read printChordDiagram echo outputFile="1" echo -n "Do you want the output sent to a file? [yn] " read yesno if [ "$yesno" == "y" ]; then echo -n "Please enter the name of the file to write (or overwrite): " read outputFile if [ "$outputFile" == "" ]; then outputFile="1"; fi echo -n "Would you like the output to be in (very basic) HTML format? [yn] " read useHtml echo -n "Fire up a Mozilla process on the generated output file? [yn] " read mozillaProcess fi echo echo -n "Do you want the output translated to standard note names? [yn] " read useStandardNames if [ "$useStandardNames" == "y" ]; then echo " By arbitrary convention, 0=B, 1=C, 2=C#, etc." echo -n " Use sharp symbol (#) or flat symbol (b)? [#b] " read sharpOrFlat fi echo echo -n "Select a number of columns and rows other than the default? [yn] " read yesno if [ "$yesno" == "y" ]; then echo "All numbers rounded down to the nearest multiple of four plus one." echo -n "Enter the number of rows: " read numRows if [ "$numRows" == "" ]; then numRows="50"; fi echo -n "Enter the number of columns: " read numColumns if [ "$numColumns" == "" ]; then numColumns="78"; fi fi echo title="Note Pattern Diagram" # default title echo -n "Do you want a title printed at the top of the page? [yn] " read printTitle if [ "$printTitle" == "y" ]; then echo -n "Enter the title here: " read title fi echo echo # Round down the row and column numbers. (( numColumns = (numColumns - 1) / 4 * 4 + 1 )) (( numRows = (numRows - 1) / 4 * 4 + 1 )) # transpose after all other options chosen markedNotes=transposeList$rootNote $markedNotes # these defs are for translating to standard note names with sed (( rs = 1 )) # start row for diagram if [ "$useHtml" == "y" ]; then (( rs = rs + 6 )); fi if [ "$printTitle" == "y" ]; then (( rs = rs + 2 )); fi (( re = rs + numRows )) # end row for diagram, 3 to cover overspill if [ "$useStandardNames" == "y" ]; then if [ "$sharpOrFlat" == "#" ]; then x0="0-"; x1="1-"; x2="2-"; x3="3-"; x4="4-"; x5="5-" x6="6-"; x7="7-"; x8="8-"; x9="9-"; xa="a-"; xb="b-" y0="B-"; y1="C-"; y2="C#"; y3="D-"; y4="D#"; y5="E-" y6="F-"; y7="F#"; y8="G-"; y9="G#"; ya="A-"; yb="A#" z0="0 "; z1="1 "; z2="2 "; z3="3 "; z4="4 "; z5="5 " z6="6 "; z7="7 "; z8="8 "; z9="9 "; za="a "; zb="b " w0="B "; w1="C "; w2="C#"; w3="D "; w4="D#"; w5="E " w6="F "; w7="F#"; w8="G "; w9="G#"; wa="A "; wb="A#" else x0="0-"; x1="1-"; x2="2-"; x3="3-"; x4="4-"; x5="5-" x6="6-"; x7="7-"; x8="8-"; x9="9-"; xa="a-"; xb="b-" y0="B-"; y1="C-"; y2="Db"; y3="D-"; y4="Eb"; y5="E-" y6="F-"; y7="Gb"; y8="G-"; y9="Ab"; ya="A-"; yb="Bb" z0="0 "; z1="1 "; z2="2 "; z3="3 "; z4="4 "; z5="5 " z6="6 "; z7="7 "; z8="8 "; z9="9 "; za="a "; zb="b " w0="B "; w1="C "; w2="Db"; w3="D "; w4="Eb"; w5="E " w6="F "; w7="Gb"; w8="G "; w9="Ab"; wa="A "; wb="Bb" fi else # null translation x0="0-"; x1="1-"; x2="2-"; x3="3-"; x4="4-"; x5="5-" x6="6-"; x7="7-"; x8="8-"; x9="9-"; xa="a-"; xb="b-" y0="0-"; y1="1-"; y2="2-"; y3="3-"; y4="4-"; y5="5-" y6="6-"; y7="7-"; y8="8-"; y9="9-"; ya="a-"; yb="b-" z0="0 "; z1="1 "; z2="2 "; z3="3 "; z4="4 "; z5="5 " z6="6 "; z7="7 "; z8="8 "; z9="9 "; za="a "; zb="b " w0="0 "; w1="1 "; w2="2 "; w3="3 "; w4="4 "; w5="5 " w6="6 "; w7="7 "; w8="8 "; w9="9 "; wa="a "; wb="b " fi { # <-- start a block, to redirect output to a file if selected (( row = 0 )) # if you change the preamble text, be sure to modify # rs and re above (outside this block scope) to fix number of lines if [ "$useHtml" == "y" ]; then echo "" echo "" echo "$title" echo "" echo "" echo "" fi if [ "$printTitle" == "y" ]; then echo $title echo (( row = row + 2 )) # these appear on the page, so count as rows fi while true do printRow 0 4 8 (( row = row + 1 )) if (( row >= numRows )); then break; fi printBetweenRows printRow 9 1 5 (( row = row + 4 )) if (( row >= numRows )); then break; fi printBetweenRows printRow 6 a 2 (( row = row + 4 )) if (( row >= numRows )); then break; fi printBetweenRows printRow 3 7 b (( row = row + 4 )) if (( row >= numRows )); then break; fi printBetweenRows (( row = row + 3 )) done echo if [ "$printChordDiagram" == "y" ]; then echo echo "Chords with root 0 (the pattern is the same for all chords):" echo echo " 9th=7th+add9" echo "3rd 3--7 5th 7 5th 7th a 2 add9 9 7th 0--4--7" echo " | / /| | / (-3rd=sus2) |" echo " |/ / | |/ | augmented" echo " 0 0--4 3rd 7--b maj7 6" echo " root root /| |" echo " / | |" echo " minor major 0--4 3" echo " /| |" echo " / | |" echo " sus4 5 9 0" echo " (-3rd) 6th" echo " diminished" echo echo "Note the cycle of 5ths along the / diagonals; counting along the \ diagonals." echo "Note guitar/bass fretboard pattern (minus \"guitar bump\") along alternate \ diags." echo "Standard note convention: 0=B 1=C 2=C# 3=D 4=D# 5=E 6=F 7=F# 8=G 9=G# a=A b=A#" echo fi if [ "$useHtml" == "y" ]; then echo " " echo "" echo "" fi } | \ sed -e "$rs,$re s/$xb/$yb/g" -e "$rs,$re s/$x1/$y1/g" -e "$rs,$re s/$x2/$y2/g" \ -e "$rs,$re s/$x3/$y3/g" -e "$rs,$re s/$x4/$y4/g" -e "$rs,$re s/$x5/$y5/g" \ -e "$rs,$re s/$x6/$y6/g" -e "$rs,$re s/$x7/$y7/g" -e "$rs,$re s/$x8/$y8/g" \ -e "$rs,$re s/$x9/$y9/g" -e "$rs,$re s/$xa/$ya/g" -e "$rs,$re s/$x0/$y0/g" \ -e "$rs,$re s/$zb/$wb/g" -e "$rs,$re s/$z1/$w1/g" -e "$rs,$re s/$z2/$w2/g" \ -e "$rs,$re s/$z3/$w3/g" -e "$rs,$re s/$z4/$w4/g" -e "$rs,$re s/$z5/$w5/g" \ -e "$rs,$re s/$z6/$w6/g" -e "$rs,$re s/$z7/$w7/g" -e "$rs,$re s/$z8/$w8/g" \ -e "$rs,$re s/$z9/$w9/g" -e "$rs,$re s/$za/$wa/g" -e "$rs,$re s/$z0/$w0/g" \ 1>&$outputFile if [ "$mozillaProcess" == "y" ]; then if [ "$outputFile" != "1" ]; then exec mozilla $outputFile fi fi  ### Command line based text replace ## sed • sed 's/Mark Monre/Marc Monroe/' 1.txt > 2.txt • find ./* -type f -exec sed -i 's///g' {} \; ## The “replace” command • Syntax: replace OLD-STRING NEW-STRING OUTPUT-FILE • Example: $ replace UNIX Linux  newfile
• Example:
$cat /etc/passwd | replace : '|' • Partial support for regular expressions: \^ – matches start of line, and$ matches end of line.
• Example: replace all IP address 192.168.1.2 start of line:
$replace \^192.168.1.2 192.168.5.10 newfile • a bash script, ‘fixer.sh’  #!/bin/bash replace CHANGEFROM CHANGETO$1.tmp rm $1 mv$1.tmp $1  now run this command line: $ grep CHANGEFROM |cut -d':' -f1 |xargs -n 1 fixer.sh

the results is that all files in the directory (or whatever you grep for) will be changed automagically.
just make sure the grep doesn’t include the fixer script itself, or it will die half-way through changing when execute permissions are reset!

## Perl

Sources:

Related: Regular expressions – https://eikonal.wordpress.com/2010/04/02/regular-expressions/ | Perl online – https://eikonal.wordpress.com/2010/02/15/perl-online/

### Enforcing password virtues in Linux

Filed under: security hardening — Tags: , , , — sandokan65 @ 11:16

Source: The Holographic Principle and the Renormalization Group, Enrique Alvarez and Cesar Gomez, arXiv:hep-th/9810102v1, 1998.10.14 – http://arxiv.org/abs/hep-th/9810102.

In terms of a real orthonormal tetrad $e^a$:

• $l :\equiv l^\mu\partial_\mu \equiv e^+ \equiv \frac1{\sqrt{2}}(e^0+e^3),$
• $n :\equiv n^\mu\partial_\mu \equiv e^- \equiv \frac1{\sqrt{2}}(e^0-e^3),$
• $m :\equiv m^\mu\partial_\mu \equiv e_T \equiv \frac1{\sqrt{2}}(e^1-i e^2),$
• $\bar{m} :\equiv \bar{m}^\mu\partial_\mu \equiv \bar{e}_T \equiv \frac1{\sqrt{2}}(e^1+i e^2).$

Properties:

• $l^2=n^2=m^2=\bar{m}^2=0$,
• $l\cdot n =1$, $m\cdot\bar{m}=-1$,
• $l\cdot m=l\cdot\bar{m}=n\cdot m=n\cdot\bar{m}=0$.

Some optical scalars:

• $\rho :\equiv - \nabla_\mu l_\nu m^\nu\bar{m}^\mu = - (\theta+i\omega),$
• $\theta :\equiv \frac12\nabla_\alpha l^\alpha \ \ (expansion),$
• $\omega^2 :\equiv \frac12\omega_{\alpha\beta}\omega^{\alpha\beta}, \ (rotation),$
• $\omega_{\alpha\beta} :\equiv \nabla_{[\alpha}l_{\beta]}.$

• $l^\mu\nabla_\mu\theta = \omega^2-\frac12R_{\mu\nu}l^\mu l^\nu - \sigma\bar{\sigma} - \theta^2.$
• Here the shear $\sigma\bar{\sigma}$ is given by: $\sigma\bar{\sigma} :\equiv \frac12\nabla_{[\alpha}l_{\beta]}\nabla^{[\alpha}l^{\beta]} - \frac14(\nabla_\alpha l^\alpha)^2.$