J.P. McCarthy: Math Page

Some Unresolved and Unexplored Aspects of Random Walks on Quantum Groups

May 14, 2019 in Quantum Groups, Random Walks on Finite Quantum Groups, Research | Leave a comment

Slides of a talk given to the Functional Analysis seminar in Besancon.

Some of these problems have since been solved.

“e in support” implies convergence

Consider a $\nu\in M_p(G)$ on a finite quantum group such that where

$M_p(G)\subset \mathbb{C}\varepsilon \oplus (\ker \varepsilon)^*$ ,

$\nu=\nu(e)\varepsilon+\psi$ with $\nu(e)>0$ . This has a positive density of trace one (with respect to the Haar state $\int_G\in M_p(G)$ ), say

$\displaystyle a_\nu=\nu(e)\eta+b_\psi\in \mathbb{C}\eta\oplus \ker \varepsilon$ ,

where $\eta$ is the Haar element.

An element in a direct sum is positive if and only if both elements are positive. The Haar element is positive and so $b_\psi\geq 0$ . Assume that $b_\psi\neq 0$ (if $b_\psi=0$ , then $\psi=0\Rightarrow \nu=\varepsilon\Rightarrow \nu^{\star k}=\varepsilon$ for all $k$ and we have trivial convergence)

Therefore let

$\displaystyle a_{\tilde{\psi}}:=\frac{b_\psi}{\int_G b_\psi}$

be the density of $\tilde{\psi}\in M_p(G)$ .

Now we can explicitly write

$\displaystyle \nu=\nu(e)\varepsilon+(1-\nu(e))\tilde{\psi}$ .

This has stochastic operator

$P_\nu=\nu(e)I_{F(G)}+(1-\nu(e))P_{\tilde{\psi}}$ .

Let $\lambda$ be an eigenvalue of $P_\nu$ of eigenvector $a$ . This yields

$\nu(e)a+(1-\nu(e))P_{\tilde{\psi}}(a)=\lambda a$

and thus

$\displaystyle P_{\tilde{\psi}}a=\frac{\lambda-\nu(e)}{1-\nu(e)}a$ .

Therefore, as $a$ is also an eigenvector for $P_{\tilde{\psi}}$ , and $P_{\tilde{\psi}}$ is a stochastic operator (if $a$ is an eigenvector of eigenvalue $|\lambda|>1$ , then $\|P_\nu a\|_1=|\lambda|\|a\|_1\leq \|a\|_1$ , contradiction), we have

$\displaystyle \left|\frac{\lambda-\nu(e)}{1-\nu(e)}\right|\leq 1$

$\Rightarrow |\lambda-\nu(e)|\leq 1-\nu(e)$ .

This means that the eigenvalues of $P_\nu$ lie in the ball $B_{1-\nu(e)}(\nu(e))$ and thus the only eigenvalue of magnitude one is $\lambda=1$ , which has (left)-eigenvector the stationary distribution of $P_\nu$ , say $\nu_\infty$ .

If $\nu$ is symmetric/reversible in the sense that $\nu=\nu\circ S$ , then $P_\nu$ is self-adjoint and has a basis of (left)-eigenvectors $\{\nu_\infty=:u_1,u_2,\dots,u_{|G|}\}\subset \mathbb{C}G$ and we have, if we write $\nu=\sum_{t=1}^{|G|}a_tu_t$ ,

$\displaystyle \nu^{\star k}=\sum_{t=1}^{|G|}a_t\lambda_t^ku_t$ ,

which converges to $a_1\nu_\infty$ (so that $a_1=1$ ).

If $\nu$ is not reversible, it is a standard argument to show that when put in Jordan normal form, that the powers $P_{\nu}^k$ converge and thus so do the $\nu^{\star k}$ $\bullet$

Total Variation Decrasing

Uses Simeng Wang’s $\|a\star_Ab\|_1\leq \|a\|_1\|b\|_1$ . Result holds for compact Kac if the state has a density.

Periodic $e^2$ is concentrated on a coset of a proper normal subgroup of $\mathfrak{G}_0$

$e_2+e_4$ is a minimal projection (coset) in the quotient space of the normal subgroup (to be double checked) given by $\langle e_1,e_3\rangle$

Supported on Subgroup implies Reducible

I believe I have a full proof that reducible is equivalent to supported on a pre-subgroup.

MATH7021: Spring 2019, Week 12

May 1, 2019 in MATH7021 | Leave a comment

Mathematics Exam Advice

The first piece of advice is to read questions carefully. Don’t glance at a question and go off writing: take a moment to understand what you have been asked to do.
Don’t use tippex; instead draw a simple line(s) through work that you think is incorrect.
For equations, check your solution by substituting your solution into the original equation. If your answer is wrong and you know it is wrong: write that on your script.

If you do have time at the end of the exam, go through each of your answers and ask yourself:

have I answered the question that was asked?
does my answer make sense?
check your answer (e.g. differentiate/antidifferentiate an antiderivative/derivative, substitute your solution into equations, check your answer against a rough estimate, or what a picture is telling you, etc)

Week 12

On Monday, and Wednesday PM, we finished the module by looking at triple integrals.

The Wednesday 09:00 lecture was a tutorial along with most of Wednesday PM and the Thursday class.

Read the rest of this entry »

MATH6040: Spring 2019, Week 12

May 1, 2019 in MATH6040 | Leave a comment

Mathematics Exam Advice

The first piece of advice is to read questions carefully. Don’t glance at a question and go off writing: take a moment to understand what you have been asked to do.
Don’t use tippex; instead draw a simple line(s) through work that you think is incorrect.
For equations, check your solution by substituting your solution into the original equation. If your answer is wrong and you know it is wrong: write that on your script.

If you do have time at the end of the exam, go through each of your answers and ask yourself:

have I answered the question that was asked?
does my answer make sense?
check your answer (e.g. differentiate/antidifferentiate an antiderivative/derivative, substitute your solution into equations, check your answer against a rough estimate, or what a picture is telling you, etc)

Read the rest of this entry »

MATH7021: Spring 2019, Week 11

April 11, 2019 in MATH7021 | Leave a comment

Assignment 2

Has been corrected and results emailed to you.

Some remarks on common mistakes here.

Week 11

We had a systems of differential equations tutorial Monday and before looking at double integrals.

Week 12

We will look at triple integrals and then have one or two tutorials on. Possibly Wednesday 09:00 for double integrals and Thursday for triple integrals.

Week 13

We will review the Summer 2018 paper.

Study

Please feel free to ask me questions about the exercises via email or even better on this webpage.

Exam Papers

These are not always found in your programme selection — most of the time you will have to look here.

Student Resources

Please see the Student Resources tab on the top of this page for information on the Academic Learning Centre, etc..

MATH6040: Spring 2019, Week 11

April 10, 2019 in MATH6040 | 6 comments

Test 2

Test 2, worth 15% and based on Chapter 3, will now take place Week 12, 30 April. There is a sample test [to give an indication of length and layout only] in the notes (marking scheme) and the test will be based on Chapter 3 only.

More Q. 1s (on the test) can be found on p.112; more Q. 2s on p. 117; more Q. 3s on p.125 and p.172, Q.1; more Q. 4s on p.136, and more Q. 5s on p. 143.

Chapter 3 Summary p. 144.

Please feel free to ask me questions via email or even better on this webpage.

Homework

Once you are prepared for Test 2 you can start looking at Chapter 4:

Revision of Integration, p.161.
p.167, Q. 1-5
p.182

Week 11

We had some tutorial time from 18:00-19:00 for further differentiation (i.e. for Test 2, after Easter).

We completed our review of antidifferentiation before starting Chapter 4 proper.

We looked at Integration by Parts and centroids.

For those who could not make it here is some video and slides from what we did after the video died.

Week 12

We will have some tutorial time from 18:00-19:00 for further differentiation.

We will have Test 2 from 19:00-20:05.

Then we will look at completing the square, centres of gravity, and work.

Week 13

We will look the Winter 2018 paper at the back of your manual.

CIT Mathematics Exam Papers

These are not always found in your programme selection — most of the time you will have to look here.

Student Resources

Please see the Student Resources tab on the top of this page for information on the Academic Learning Centre, etc.

MATH7021: Spring 2019, Week 10

April 4, 2019 in MATH7021 | Leave a comment

Week 10

We had two additional tutorials… actually four tutorials in total and two lectures; the lectures focused on Systems of Differential Equations.

Assignment 2

Assignment 2 now has a pushed back deadline of 12:00, 12 April: the Friday of Week 11. Assignment 2 is in the manual, P. 164. Usual warnings about copying apply.

Week 11

We will have a systems of differential equations tutorial Monday and then look at double integrals.

Week 12

We will look at triple integrals and then have one or two tutorials. Possibly Monday for double integrals and Thursday for triple integrals.

Week 13

We will review the Summer 2018 paper.

Study

Please feel free to ask me questions about the exercises via email or even better on this webpage.

Exam Papers

These are not always found in your programme selection — most of the time you will have to look here.

Student Resources

Please see the Student Resources tab on the top of this page for information on the Academic Learning Centre, etc..

MATH6040: Spring 2019, Week 10

April 3, 2019 in MATH6040 | 2 comments

Test 2

Test 2, worth 15% and based on Chapter 3, will now take place Week 12, 30 April. There is a sample test in the notes and the test will be based on Chapter 3 only.

Homework Exercises

If you do any of the suggested exercises you can give them to me for correction. Please feel free to ask me questions about the exercises via email or even better on this webpage.

I recommend strongly that everyone completes P.102, Q.1.

After that you can look at:

P.136, Q.1-3
P. 143, Q. 1-4
P. 125, Q. 1-4, P.172, Q.1
P. 117, Q. 1-4
P.112, Q. 1-5
Sample Test 2, P.145

If you want to do more again, look at P.113, Q.6-9, P. 118, Q. 5-6, P. 125, Q.5. There is a Weekly Summary for the Chapter 3 Material on P.144.

If you read on there is some information below about solutions to these exercises.

Week 10

For those who were able to make it we had some tutorial time from 18:00-19:00 for parametric, implicit, and related rates differentiation. If you are really interested in understanding how does a curve have an equation, see here.

In class we looked at partial differentiation and error analysis. For those who could not make it, here is video of the partial differentiation material and here are the slides from the error analysis (the video died shortly after we started error analysis).

We only started a revision of Antidifferentiation to start Chapter 4 on (Further) Integration. I have this section completed here.

Week 11

We will have some tutorial time from 18:00-19:00 for further differentiation (i.e. for Test 2, after Easter).

We are under pressure for time but I have made the decision that we will be better off completing our review of antidifferentiation before starting Chapter 4 proper. This might put us under time pressure later on but I believe it is the correct thing to do.

We will look at Integration by Parts, completing the square, and work.

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MATH7016: Final Weekly Summary

April 2, 2019 in MATH7016 | Leave a comment

VBA Assessment 1 & Written Assessment 1 – Results

VBA Assessment 1 Results have been emailed and I hope to have your Written Assessment 1 Results to ye Wednesday or Thursday.

Week 10

We looked at finite differences for the Heat Equation. This completes the examinable written material.

In VBA we implemented same.

Week 11 — 2nd 20% VBA Assessment

I will be in B242 from 08:30 – 09:00 to help with any questions, ideally the p. 146 tutorial equations. This is extra time that I am making myself available but it is just an option for you.

This tutorial time will continue in B242 until 09:55.

In the 12:00 class we will have a revision session, geared towards the 40% Written Assessment 2.

To understand how your student numbers generate constants (see below) see this VBA Test 2 from 2017 (do not read this as a sample – it included e.g. the Heat Equation which you will not be examined on and the Laplace’s Equation might be slightly simpler than what ye will have).

Your VBA 2 Assessment will consist of three questions:

shooting method
finite differences; steady state temperature uninsulated rod (more P. 90)
Laplace’s Equation

Formulae will be provided in the VBA 2 Assessment.

See last weeks’ Summary for more detail on the VBA 2 assessment.

Week 12 — 40% Written Test — After Easter

There will be no 12:00 class but I will be in B242 from 08:00 until about 08:40 for any last minute questions.

The 40% Written Assessment will be broken up into two parts.

Theory Element Tuesday 30 April, Melbourne Rows E-G, 09:00 (30 minutes worth but given an hour).

It will be geared more towards theoretical questions. Please see P. 108-110. More questions p.84, Q. 3.

Calculation Element in your Week 12 VBA time and lab, (45 minutes worth but given an hour and 45 minutes)

The second part of the Test will take place in your VBA slot. I have to tell you in advance what questions are coming up so let us say

Second Order Problem Using Heun’s Method
Heat Flux Density at a Point (p.101)
Heat Equation

Each group will get questions with only minor variations from the sample questions p. 111 (more Q. 1 on P.55).

Formulae will be provided in the Written Assessment 2.

Study

Study should consist of

doing exercises from the notes
completing VBA exercises

Student Resources

Please see the Student Resources tab on the top of this page for information on the Academic Learning Centre, etc.

Final Concept MCQ League Table

Unfortunately with my illness this kind of ran of steam so this is the final standings.

league5

Please ask questions in the lab about questions you have gotten wrong.

MATH7016: Weeks 8 & 9

March 29, 2019 in MATH7016 | Leave a comment

VBA Assessment 1 & Written Assessment 1 – Results

I have been very ill over the last two weeks but have gotten some meds from the doctor and hope to get these back to you ASAP.

Weeks 8 & 9

I missed the 09:00 class on the Tuesday of Week 8 with illness.

In the afternoon, we did two examples: of the Shooting Method and of Finite Differences (for the temperature along a rod). Please see Shooting_and_FiniteDifferences_Examples.

In Week 9, we started looking at partial differential equations by looking at Laplace’s Equation.

In VBA, in Week 8 we had MCQ VI and we did the Boundary Value Problems lab.

In VBA, in Week 9 we did the Laplace Equation Lab (which also had some 1-d boundary value stuff). I will email on a VBA file of the 1-D finite differences problem.

This completes the examinable VBA material. The Heat Equation that we cover in Week 10 will not be examinable.

Week 10

We will look at finite differences for the Heat Equation. This completes the examinable written material.

In VBA we will implement same.

Read the rest of this entry »

MATH7021: Spring 2019, Weeks 8 & 9

March 28, 2019 in MATH7021 | Leave a comment

Weeks 8 & 9

Week 8 was a disaster. We missed out on Monday due to St Patrick’s Day. We missed out on Wednesday morning because of my man flu. Thursday I had to go to Dublin for a funeral.

Week 9 we managed to get everything done so that you can now do Assignment 2.

We had two tutorials in Week 9

Week 10

We have two additional classes:

Monday 09:00, B189

Thursday 14:00, E6

So we have six classes

Monday x 2

Wednesday x 2

Thursday x 2

The following classes will be tutorials:

Monday x 2

Wednesday 09:00

Thursday 14:00

Wednesday 14:00 and Thursday 10:00 will be lectures, focused on Systems of Differenial Equations.

Read the rest of this entry »

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J.P. McCarthy: Math Page

“e in support” implies convergence

Total Variation Decrasing

Periodic is concentrated on a coset of a proper normal subgroup of

Supported on Subgroup implies Reducible

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Mathematics Exam Advice

Week 12

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Mathematics Exam Advice

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Assignment 2

Week 11

Week 12

Week 13

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Exam Papers

Student Resources

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Test 2

Homework

Week 11

Week 12

Week 13

CIT Mathematics Exam Papers

Student Resources

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Assignment 2

Week 11

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Week 13

Study

Exam Papers

Student Resources

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Test 2

Homework Exercises

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VBA Assessment 1 & Written Assessment 1 – Results

Week 10

Week 11 — 2nd 20% VBA Assessment

Week 12 — 40% Written Test — After Easter

Study

Student Resources

Final Concept MCQ League Table

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VBA Assessment 1 & Written Assessment 1 – Results

Weeks 8 & 9

Week 10

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Weeks 8 & 9

Week 10

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Periodic $e^2$ is concentrated on a coset of a proper normal subgroup of $\mathfrak{G}_0$