14 years ago
Sunday, May 30, 2010
M Theory Lesson 334
For the usual choice of $3 \times 3$ Fourier matrix, the transformed matrix $M = R_{23}(a) R_{12}(b) R_{31}(c)$ takes the form where we note that the first component is fully fixed by $F_3$. This neatly illustrates the $(1,2)$ block form of transformed magic mixing matrices, which is basically a combination of the diagonal of $1$-circulant eigenvalues and a $2$-circulant codiagonal. For each $R_2$ factor, there is an $F_3$ transform that fixes it. It follows that for a suitable twisted Fourier transform, the whole triple product will remain fixed.
Saturday, May 29, 2010
B Mesons Again
Resonaances reports that CDF have just released results that conflict with the D0 claim about $B$ mesons, at a conference: measuring CP violation in $B_s$ decays, they find the data are consistent with Standard Model expectations.
Wednesday, May 26, 2010
M Theory Lesson 333
Recall that the $2 \times 2$ $R_2$ matrix is only one of three MUB matrices, namely the one corresponding to the Pauli matrix $\sigma_{Y}$. We could consider $3 \times 3$ product forms using the MUB matrices for $X$ or $Z$ directions. Recall that these are, respectively, a Fourier matrix and the identity matrix. But a mixed $XYZ$ product results in the same two factor (tribimaximal type) form, since a scaled identity does not alter the mixing matrix, and the use of $i F_2$ only affects the phases.
Tuesday, May 25, 2010
M Theory Lesson 332
If we vary $b$ over a large positive range, while keeping $a$ and $c$ at their CKM values, the CP phase $2 \beta_s$ varies over all angles $\in \{ 0, - \pi \}$, slowly approaching $- \pi$ for very large $b$. This variation does not greatly alter the five large CKM entries, or the entry corresponding to $c$, but it does move the probability matrix well away from current experimental bounds. At small $b$, the phase $2 \beta_s$ (called phi on the graph) goes like $2abc$.
Quote of the Week
Our views of the physical world are changing rapidly. Humanity's continuing search for coherent structures in physics, biology, and cosmology has frequently led to surprises as well as confusion. Discovering new phenomena is one thing, putting them into context with other pieces of knowledge, and inferring their fundamental consequences is quite something else. There are controversies, differences of opinion, and sometimes even religious feelings which come into play. These should be discussed openly.From the website of the journal Foundations of Physics, which appears to have accepted Carl Brannen's paper on spin path integrals. Congratulations, Carl.
Science Excellence
FSP reports on Canada's embarrassing inability to include any women in the short list of 36 for its Excellence Research chairs. For those of you who are logic challenged, with no women on the shortlist the final list was inevitably all white male (OK, so there was one south Asian looking guy). The chairs cover a broad range of fields, including life sciences subjects that are well represented by women.
The Canadian government managed to find a few ill informed apologists to suggest reasons why this may have happened, without putting too much emphasis on outright discrimination in academia. Some universities tried to, er, set things right in the usual manner, by hiring the chairs' spouses. One often hears complaints that affirmative action for women in science causes a drop in standards, but research shows that on the rare occasion that such measures are actually implemented, the women perform better, on average, than their male colleagues, and this is without taking into account the documented bias in judging the value of a woman's research.
Ah, the world of 2010. Those poor innocent Canadians forgot to do what they do in other countries: add a token woman or two to look good. Well, they won't forget next time. If they wise up, they can keep the old boys club going until, oh, maybe 2099. Oh, that's right, silly me. We'll all be starving and illiterate by then ...
The Canadian government managed to find a few ill informed apologists to suggest reasons why this may have happened, without putting too much emphasis on outright discrimination in academia. Some universities tried to, er, set things right in the usual manner, by hiring the chairs' spouses. One often hears complaints that affirmative action for women in science causes a drop in standards, but research shows that on the rare occasion that such measures are actually implemented, the women perform better, on average, than their male colleagues, and this is without taking into account the documented bias in judging the value of a woman's research.
Ah, the world of 2010. Those poor innocent Canadians forgot to do what they do in other countries: add a token woman or two to look good. Well, they won't forget next time. If they wise up, they can keep the old boys club going until, oh, maybe 2099. Oh, that's right, silly me. We'll all be starving and illiterate by then ...
Monday, May 24, 2010
M Theory Lesson 331
To summarize the unitary $(a,b,c)$ parameterization: the CKM probabilities are obtained from the three values
$(a,b,c) = (-0.2314, 24, 0.0035)$,
which result in the angle $\beta_s = 0.0194 \simeq abc$. This value for $\beta_s$ is in perfect agreement with Standard Model fits.
$(a,b,c) = (-0.2314, 24, 0.0035)$,
which result in the angle $\beta_s = 0.0194 \simeq abc$. This value for $\beta_s$ is in perfect agreement with Standard Model fits.
Sunday, May 23, 2010
Twistors and Mass
Already by the early 1980s, some progress had been made on understanding massive states within the twistor program of Roger Penrose. In particular, the mass parameter of the Klein Gordon equation could be seen as arising from configurations of not one, but several twistors. For example, Andrew Hodges, the main developer of twistor diagram methods, wrote a paper about this way back in 1984.
The pivotal mathematical idea is discussed in this 1981 paper by Hughston and Hurd. That is, the description of rest mass requires higher cohomology, which may be built from the one dimensional cohomology associated to massless fields.
In my mind, this cohomological fact was always one of the strongest motivations for the study of category theory, and abstract cohomology, in the foundations of physics. Now, with the new success of twistor theory in scattering amplitudes for QFT, one can only agree with Penrose's sentiment that it is high time we revisited cohomological studies of rest mass.
The pivotal mathematical idea is discussed in this 1981 paper by Hughston and Hurd. That is, the description of rest mass requires higher cohomology, which may be built from the one dimensional cohomology associated to massless fields.
In my mind, this cohomological fact was always one of the strongest motivations for the study of category theory, and abstract cohomology, in the foundations of physics. Now, with the new success of twistor theory in scattering amplitudes for QFT, one can only agree with Penrose's sentiment that it is high time we revisited cohomological studies of rest mass.
Saturday, May 22, 2010
Gravity Research
This year's Gravity Research Foundation first prize goes to Van Raamsdonk's stringy paper about building spacetime with entanglement. It seems that the popularity of quantum information theory is rapidly growing amongst stringers. Other winning essays include Marolf's, on extreme black holes, and Mathur's membrane paradigm paper.
Friday, May 21, 2010
New Physics at D0
It boggles the mind how few people find this interesting. Anyway, as reported in the new physics paper of D0 (those are real physicists), in equation $(A26)$ we see that the Standard Model estimate for $\beta_s$ is $0.019 \pm 0.001$, which is in exact agreement with my fit for the $R(a)R(b)R(c)$ form. The reported new physics, which is currently at $3.2 \sigma$, must bring further CP violation into $B$ physics through a mechanism beyond basic information mixing. However, since the Standard Model cannot possibly account for this observation, one cannot help but conclude that the information mixing result is the correct place from which to investigate possible extensions to the $R(a)R(b)R(c)$ form.
Thursday, May 20, 2010
F Theory
Our commenter Mitchell is keen to link our mixing matrices to phenomenology from F Theory. Recall that F Theory is a $12$ dimensional theory, so for us this is the $12$ dimensions we get from counting, say, quarks, or the $12$ dimensions we get from counting marked points and holes on the three complex moduli of twistor dimension, namely $M(0,6)$, $M(1,3)$ and $M(2,0)$. Anyway, lo and behold, Mottle writes today about a brand new arxiv paper on Fuzzy F Theory ... and why the number $24$ should be taken seriously (by stringers at least) as an exact coupling parameter.
M Theory Lesson 330
If we plot the nine entries for the two factor matrix $R(a)R(b)$, we obtain a nice grid in the complex plane where it is easy to see that the four interesting phases are given by
$\textrm{tan}^{-1} (a)$, $\textrm{tan}^{-1} (b)$, $\textrm{tan}^{-1} (1/a)$, $\textrm{tan}^{-1} (1/b)$.
Observe that the angle between the $(-1 + bi)$ line and the $(ab + ai)$ line is $\pi / 2$. Similarly for the other two interesting angles. That is, the eight non zero matrix entries form four sets of right angles. Thus the parameters $a$ and $b$ account for essentially only two independent phases in the mixing matrix $R(a)R(b)$.
Note also that for the CKM values, the three phases $(tb)$, $(bc)$ and $(cs)$ cancel out, leaving the $(ts)$ term to account for $2 \beta_s = 0.04$. Moreover, the $(cs)$ phase is $\pi / 2$, and $(tb)$ and $(bc)$ sum to $\pi /2$.
$\textrm{tan}^{-1} (a)$, $\textrm{tan}^{-1} (b)$, $\textrm{tan}^{-1} (1/a)$, $\textrm{tan}^{-1} (1/b)$.
Observe that the angle between the $(-1 + bi)$ line and the $(ab + ai)$ line is $\pi / 2$. Similarly for the other two interesting angles. That is, the eight non zero matrix entries form four sets of right angles. Thus the parameters $a$ and $b$ account for essentially only two independent phases in the mixing matrix $R(a)R(b)$.
Note also that for the CKM values, the three phases $(tb)$, $(bc)$ and $(cs)$ cancel out, leaving the $(ts)$ term to account for $2 \beta_s = 0.04$. Moreover, the $(cs)$ phase is $\pi / 2$, and $(tb)$ and $(bc)$ sum to $\pi /2$.
Tuesday, May 18, 2010
M Theory Lesson 329
There are $27$ possible numerators in the cubic analogue of the two $R_2$ factor probability set. As noted earlier, the CKM matrix approximates this tribimaximal double product for three parameters, set to $(a,b,c)$ $=$ $(-0.231, 24, 0.0035)$. In terms of cubic numerators, the CKM entries take the very simple form: which one may easily verify on an old calculator, remembering to normalise and take square roots. Once again the $(td)$ term is a little higher than expected. The third variable $c$ only enters as the $(ub)$ correction to tribimaximal type mixing. The astute reader will see that this $(ub)$ term destroys the unitarity of the CKM matrix, although unitarity is restored in the full product form.
Monday, May 17, 2010
M Theory Lesson 328
Even when reducing to $2 \times 2$ submatrices, the scaled $R_2$ factors define a basis for a three dimensional space via their column vectors. Let us consider how the two parameters $(a,b)$ give rise to a tribimaximal type probability matrix.
When two bases are mutually unbiased, the inner product of the column vectors between bases always gives the same result. That is, the probabilities are all equal. For two distinct $R_2$ factors, on the other hand, the nine possible column products are all distinct! With the denominator $(a^2 + 1)(b^2 + 1)$ (for the squares) we have the nine numerators: For the neutrino mixing choice of $(a,b) = (\sqrt{2}, 1)$ we observe that these nine numbers become the entries of the tribimaximal matrix. In order to generalise to the $27$ possibilities for three variables, we will place these $9$ numbers in a square, which is basically the mixing matrix. Interpreting the zero as $(a^2 + 1)(b^2 + 1)$, the three points on the edges all obey the sum rule $P + Q = R$. This rule extends naturally to the cube in three dimensions, where the three parameters $(a,b,c)$ are symmetrically represented.
When two bases are mutually unbiased, the inner product of the column vectors between bases always gives the same result. That is, the probabilities are all equal. For two distinct $R_2$ factors, on the other hand, the nine possible column products are all distinct! With the denominator $(a^2 + 1)(b^2 + 1)$ (for the squares) we have the nine numerators: For the neutrino mixing choice of $(a,b) = (\sqrt{2}, 1)$ we observe that these nine numbers become the entries of the tribimaximal matrix. In order to generalise to the $27$ possibilities for three variables, we will place these $9$ numbers in a square, which is basically the mixing matrix. Interpreting the zero as $(a^2 + 1)(b^2 + 1)$, the three points on the edges all obey the sum rule $P + Q = R$. This rule extends naturally to the cube in three dimensions, where the three parameters $(a,b,c)$ are symmetrically represented.
Sunday, May 16, 2010
M Theory Lesson 327
Thanks to Carl Brannen, I took a look at this 2005 paper by Bjorken, Harrison and Scott. In this paper, the tribimaximal mixing matrix is extended by a one parameter factor not unlike that of the third $R_2$ factor in $M$. Moreover, their parameter is also closely related to a near zero mixing matrix entry.
As pointed out in the paper, unitarity triangles now take a simpler form. We saw that the $M$ phases, for $(a,b,c)$ $=$ $(-0.231, 24, 0.0035)$, give a value of $0.04$ for the $2 \beta_s$ parameter. This angle comes mostly from the $(ts)$ term, since the other three angles in $2 \beta_s$ roughly cancel out.
As pointed out in the paper, unitarity triangles now take a simpler form. We saw that the $M$ phases, for $(a,b,c)$ $=$ $(-0.231, 24, 0.0035)$, give a value of $0.04$ for the $2 \beta_s$ parameter. This angle comes mostly from the $(ts)$ term, since the other three angles in $2 \beta_s$ roughly cancel out.
Saturday, May 15, 2010
Welcome Jessica
Welcome back to Jessica Watson, who has just arrived in Sydney harbour. She will soon be celebrating her 17th birthday.
Monday, May 10, 2010
Upcoming FFP11
Quote of the Week
From one of my anonymous heroines:
Kea, I used to think that they win if we leave. Now I think the only way we'll win is if we leave. In droves. Then they'll have to fund studies to find out why we're leaving. Then they'll overhaul the system. It won't happen fast enough to help people like us in general.
Sunday, May 9, 2010
M Theory Lesson 326
Recall the basic MUB operator We often say that $R_{3}^{3}$ is the identity, but strictly speaking it is $-i \cdot \mathbf{1}$. In quark boson notation, where phases are written as powers of the angle $\pi / 6$, we have and so on. That is, the true relation is $R_{3}^{12} = \mathbf{1}$. As always, the Fourier matrix satisfies $F^{4} = \mathbf{1}$. This is analogous to the rule $R_{2}^{8} = \mathbf{1}$ for the $2 \times 2$ operator, which also relies on the complex number $i$. The Fourier matrix encourages the circulant $R_d$ matrices to take on that extra factor of four. So in dimension $6$, which is the best dimension for studying the particle spectrum, we would have an $R_6$ operator obeying $R_{6}^{24} = \mathbf{1}$. If we rephased the matrix $R_3$ by the factor $-i$, then the cubic rule is obeyed. This matrix is in fact precisely a quark boson matrix for $\overline{u}_{L}$.
Saturday, May 8, 2010
Top Down Numbers
From a PDG review:
With this fit, the parameter $2 \beta_{s}$ comes out to be $0.03877$. This is in disagreement with our old rough (and strangely viable) value (Carl's circulant sum now gives a result of about $0.05$) but in mysteriously good agreement with the Standard Model fit for $2 \beta_{s}$.
Update: OK, so I have now checked the old estimate carefully. The difference between the $0.04$ and the larger value (roughly $0.9$) comes down to the signs used in the $(cb)$ term. The value $0.04$ is correct.
Case 1: The $0.04$ value comes from taking $0.2275 + 1.000809 i$ as the conjugate of the term in $M$ (unnormalised), which is the natural thing to do. In this case, the three angles for $(tb)$, $(cs)$ and $(cb)$ all cancel, and the $0.04$ basically comes from the phase for the $(ts)$ term, which is $0.019386$ radians.
Case 2: The larger value may be obtained from adjusting the phased CKM matrix so that the terms in the $2 \beta_s$ ratio have matching signs. That is, it takes $0.2275 - 1.000809 i$, in which case the $1.347278$ does not cancel and the $2 \beta_s$ value is now around $0.9$. This is the same as taking $V_{cb}$ instead of $V_{cb}^{*}$. I cannot see a good reason for doing this.
The CKM elements $| V_{td} |$ and $| V_{ts} |$ cannot be measured from tree level decays of the top quark, so one has to rely on determinations from $B \overline{B}$ oscillations mediated by box diagrams or loop mediated rare K and B decays. Theoretical uncertainties in hadronic effects limit the accuracy of the current determinations.The 2008 review suggests that $| V_{td} / V_{ts} | < 0.216$, and this bound is broken by the parameter fits (which used this data) in recent posts. Although this fit was rough, it yields a value of $0.242$, which is significantly higher than the Fermilab estimate. It is still within the other bounds given by $B$ and $K$ rates. Note, however, that the current best estimates for CKM parameters also puts $| V_{td} / V_{ts} | $ at too high a value, so perhaps one should not take this bound too seriously, since it relies on Standard Model calculations.
With this fit, the parameter $2 \beta_{s}$ comes out to be $0.03877$. This is in disagreement with our old rough (and strangely viable) value (Carl's circulant sum now gives a result of about $0.05$) but in mysteriously good agreement with the Standard Model fit for $2 \beta_{s}$.
Update: OK, so I have now checked the old estimate carefully. The difference between the $0.04$ and the larger value (roughly $0.9$) comes down to the signs used in the $(cb)$ term. The value $0.04$ is correct.
Case 1: The $0.04$ value comes from taking $0.2275 + 1.000809 i$ as the conjugate of the term in $M$ (unnormalised), which is the natural thing to do. In this case, the three angles for $(tb)$, $(cs)$ and $(cb)$ all cancel, and the $0.04$ basically comes from the phase for the $(ts)$ term, which is $0.019386$ radians.
Case 2: The larger value may be obtained from adjusting the phased CKM matrix so that the terms in the $2 \beta_s$ ratio have matching signs. That is, it takes $0.2275 - 1.000809 i$, in which case the $1.347278$ does not cancel and the $2 \beta_s$ value is now around $0.9$. This is the same as taking $V_{cb}$ instead of $V_{cb}^{*}$. I cannot see a good reason for doing this.
Friday, May 7, 2010
M Theory Lesson 325
Recall that the $2 \times 2$ matrix $R_{2}^{8}$ is the identity. This has a few fun consequences for the $R_2$ factors in mixing matrices. Physicists like to think of the CKM matrix as a product of up and down factors. The properties of $R_2$ mean that the mixing factor with parameter $r$ may be itself factored into several copies of the same $R_2$ type. That is, $R(r) = R(1)R(1)R(1/r)$. At an intermediate stage, we find for example that $R(24) = R(1)R(25/23)$. Taking powers of scaled $R_2$ factors we find occasional nice results, such as which displays the Pythagorean triple $(7,24,25)$. There are many ways to factor these scaled matrices into two or more components.
Thursday, May 6, 2010
Falsifying Paradigms
I can't watch it myself, but I suspect that this talk (Falsifying Paradigms for Cosmic Acceleration) by Dragan Huterer may be interesting.
Tuesday, May 4, 2010
M Theory Lesson 324
In the $(a,b,c)$ parameterisation, with $a = -0.231$ and $b = 24$, the value of $c$ was very small. Now a zero $r$ in an $R_2$ factor gives a weak identity, since the factor only rephases and switches rows or columns. In other words, setting $c = 0$ in a triple $R_2$ product results in a two factor product, like the tribimaximal neutrino mixing matrix.
Since $c$ is small, setting it to zero does not substantially alter the matrix entries. In fact, we observe that the parameter values $(a,b,c) = (-0.231,24,0)$ maintain all experimental CKM values except for the smallest entry, which is now forced to zero. Thus the $(ub)$ term may be considered as a correction to a tribimaximal form of the CKM matrix.
Since people are so unhappy with parameters, I will do my best to reduce the number even further in future.
Since $c$ is small, setting it to zero does not substantially alter the matrix entries. In fact, we observe that the parameter values $(a,b,c) = (-0.231,24,0)$ maintain all experimental CKM values except for the smallest entry, which is now forced to zero. Thus the $(ub)$ term may be considered as a correction to a tribimaximal form of the CKM matrix.
Since people are so unhappy with parameters, I will do my best to reduce the number even further in future.
The Electronic Mob
Woit mentions a recent spat where Nobel laureate Brian Josephson was uninvited to a nice conference at a cushy institute in Italy. The organiser in question is Antony Valentini, whose email was posted on Josephson's website. I met Valentini at PI some years ago, when he was a supposedly struggling Foundations person, but it seems that he now has a successful career through FQXi funding. After Woit's post Valentini felt it necessary to post a comment, which ended with a recommendation that people who post emails on websites should read the book, Against the Machine: Being Human in the Age of the Electronic Mob. Hence this post. First, note that Valentini's explanation of his uninvitation was:
The email I wrote was an attempt to deal with a difficult and complex organisational problem internal to the conference.Translation: some people at Imperial, perhaps not Valentini personally, like to protect the university's fine reputation. Valentini seems to think this is OK, because that's how things work, right? But he realises that
The internet is an evolving medium, and one can query the suitability of standard constraints in this context.Oh, yes, we can. And we will. Let us not forget the guy with the broken guitar, whose YouTube video resulted in a $10%$ fall in stock value for United Airlines. An Electronic Mob it may be, but revolutionary mobs are not merely noisy crowds. And I would like somebody to explain to me how I'm less human than people who play 20th century politics.
Monday, May 3, 2010
M Theory Lesson 323
The fact that $0.999133^2 = 24^2 / (24^2 + 1)$ in this parameterisation suggests looking for a CKM representation with a denominator of $24^2 + 1$. That is, if we subtract $24^2$ from the three large CKM entries on the diagonal, the remaining entries should have row and column sums of $1$. Let us look for two components: a sum $1$ piece and a zero sum piece. This can be done with a sum $1$ piece given by: leaving zero sum corrections given by where $\epsilon$ can be zero to within experimental precision. Note that the $704/24$ is just $29$ and a third. This is the norm square matrix, so on taking square roots, the $144$ becomes $12$ and so on. Numerology, maybe, but $0.999133$ still matches an $R_2$ factor at $r = 24$.
Sunday, May 2, 2010
M Theory Lesson 322
Observe that the choice of coefficients $(r,1)$ in a scaled $R_2$ factor is the general case for a super magic circulant, because scale factors will always be absorbed into the normalisation. Under an interchange of the real and complex parameters in $M$, the row sums and norm square sums remain unaltered. This means that $(r,1)$ is equivalent to $(r^{-1},1)$, a kind of S duality. For example, in the tribimaximal case it doesn't matter if we use $\sqrt{2}$ or $\sqrt{2}^{-1}$. This is an inversion of parameters with respect to the unit circle, as in Thus magic circulants, although very simple, provide an interesting parameter space in which to study mixing matrices. Note that the inverse of an $R_2$ factor is given by sending $i$ to $-i$, so we might think of the (charged lepton) identity mixing matrix as two inverse $R_2$ factors with parameters $a = r$ and $b = -r$. This gives three parameters in total for lepton mixing.
Saturday, May 1, 2010
M Theory Lesson 321
And now, without any cheating whatsoever, let us look at the full matrix $M$ with a normalisation given by $(a^2 + 1)(b^2 + 1)(c^2 + 1)$. It is a little difficult to fiddle the parameters by hand, but I managed to get all but one of the CKM parameters to within experimental precision: Note that the choice of $b = 24$ appears to be quite optimal, but I was not doing any real optimization.
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