Robert B. Kusner

Director of the Center

(This page is like a cathedral: always under reconstruction ;-)

Kusner's Math Classes

Speaking of photos: here's a link to Rob's old class photos.

This Semester

Rob is chairing and teaching Math 235: Introduction to Linear Algebra during the 2019 Spring semester. Here's how to get the e-text and sign up for on-line homework for Rob's sections (6 and 7) only! Course-wide logistical details appear here.

For those of you who have yet to officially enroll: please come to class, introduce yourself, and in a short time we should be able to officially enroll you (we don't want to deal with over-rides until we know they're necessary).

You may enjoy reviewing Basic Linear Algebra in 7 Easy Pages prepared by my former student (2011-14) Andrew Maurer (he's now in grad school at the University of Georgia; and his advisor Dan Nakano took my linear algebra course at Berkeley in the early 1980's - years later Dan told me that my course made him want to become a mathematician).

For you hardcore linear algebra students: the usual multiplication algorithm has complexity O(n^3) for n × n matrices; here's a recent paper on the latest complexity bound: O(n^2.3726...). (Conjecture: O(n^2) is best.)

Note: The last part of the course uses the relation AE=ED (for any matrix E whose columns form a basis of real eigenvectors of a real 2 × 2 matrix A with distinct real eigenvalues) to factor A=EDE^{-1}, where D is the real diagonal 2 × 2 matrix whose nonzero entries are the eigenvalues, i.e. A is similar to D. This is useful to compute powers of A and the exponential of A. But what if A has repeated real eigenvalue (a, a), or if the eigenvalues are complex conjugate pairs (a+bi, a-bi) with nonzero b? How does one decompose A=aI+bJ where J^2=-I in the latter case, or decompose A=aI+N where N^2=0 in the former? Some texts (e.g. Bretscher) find a 2 × 2 matrix aI+bJ_o to which A is similar; here J_o is the standard 90-degree rotation matrix. Here's another approach, suggested by my emeritus colleague Arunas Rudvalis, which seems simpler - and more general since it also deals with the N (nilpotent) case.

Last Semester

Rob was again teaching Advanced Multivariate Calculus (Math 425) in Fall 2018 (please see my comments below).

Advice (for those of you in Math 425):

The texts are as before: search for Calculus on Manifolds to find a .pdf of Spivak's beautiful text since it seems to be out of print (outside of China); the Marsden & Tromba text is a good resource and various recent editions should be available in used form; you should try to get - and begin reading! - both of these before the semester begins. And my former student, Kate Donoghue, is working with me on a what we hope will be a helpful set of course notes and exercises (when it's ready - you'll find them here!

Before taking Math 425, students are expected to have a good understanding of basic linear algebra (Math 235) and vector calculus (Math 233); so if you're feeling a bit "rusty" in these area, please "brush up" before the semester begins. Here's what I wrote to one prospective student:

Hi Dxxxx,

You should take a look at Marsden & Tromba's book and be sure you know about partial derivatives and multiple integrals; how to find critical points of functions of 2 or more variables, and test whether they're max, min, saddles or otherwise; and maybe a bit about finding critical points when the variables are constrained to the level set of another function (Lagrange multipliers). Although we'll (quickly!) review some of this in the first few weeks, and "remind" (I hope) you of the differential operators div, grad & curl, it's best if you've made an effort over the break!

Best,

Rob

Last Spring

Rob taught Advanced Multivariate Calculus (Math 425.1) last Spring. He also was teaching a large section of Ordinary Differential Equations (Math 331.7), a course chaired by Jinguo Lian.

Recent

Rob taught Advanced Multivariate Calculus (Math 425) in the Fall 2017 semester.

Rob chaired and taught Introduction to Linear Algebra (Math 235) during the 2017 Spring semester. Logistical details appear here.

Less Recent

Rob taught Advanced Multivariate Calculus (Math 425) in the Fall 2016 semester.

During AY 2015-16, Rob was on sabbatical: the winter, spring and summer at MSRI in Berkeley; the fall at Penn, where he taught Geometric Variational Problems (Math 299/550), a topics course for advanced undergraduates and interested graduate students.

In the spring of 2015 Rob was teaching Honors Multivariable Calculus (Math 233H). Here's the ASCII page for Math 233H homework schedule and notes.

During the fall of 2014 Rob chaired - and taught two (double) sections (3 and 4) of - Introduction to Linear Algebra (Math 235). The next few paragraphs reflect past and foreshadow future versions of that course.

Here's a link to both our sections' S14 Math 235 WeBWorK. There will be roughly one problem set each week, usually due Tuesday evenings. Please start with the "Orientation" set to help you learn WeBWorK syntax. Over the years WeBWorK has improved, but occasionally you'll find a bug! If you're sure that you've figured out a problem, but WeBWorK won't swallow your answer, please don't waste time guessing and plugging -- each problem is "worth" so little anyway -- better if you've developed the skill and confidence to KNOW you've found a real bug, and not just made a silly mistake: such is life!

Here is the (draft ASCII) Math 235 (Linear Algebra) homework schedule for Rob's section.

Here's an evolving link to common course guidelines, suggested homework and practice exam problems.

During Spring 2014, Rob taught honors Differential Geometry of Curves & Surfaces (Math 563H).

Here is the (quick-loading, even on a slow connection) ASCII file for Math 563H (Curves and Surfaces) topics & problems. We are also working up a .tex/.pdf version....

Rob also taught (a double) section 2 of Introduction to Linear Algebra (Math 235) in Spring 2014.

In Fall 2013, Rob taught (a double) section 3 of Introduction to Linear Algebra (Math 235). Here's a link to Rob's F13 Math 235 WeBWorK.

Here's a link to Math 235 Common Midterm Review Problems which Prof. Paul Hacking will go over with you from 7-8:30 on Tuesday evening 12 November 2013 in Thompson 102.

Here are links to Math 235 Common Final Review Problems and Solutions which Prof. Paul Hacking went over from 7-8:30 on Tuesday evening 10 December 2013.

And here is a link to Fall 2013 Linear Algebra (Math 235) common guidelines.

In Spring 2013, Rob taught honors Differential Geometry of Curves & Surfaces (Math 563H). Here is the (quick-loading, even on a slow connection) ASCII file for Math 563H (Curves and Surfaces) topics & problems .

Rob also served as course chair for, and taught (a double) section 3 of Introduction to Linear Algebra (Math 235).

For the past several semesters, instructors have followed these Math 235 (Linear Algebra) common guidelines.

You can find some practice final exams below, but the following four may be the most helpful to review, along with your WeBWorK:

Math 235 Practice Final Problems from Fall 2008 , ... Spring 2009 , ... Fall 2009 and from Fall 2011 .

MAKE-UPS (only pre-approved according to UMass guidelines) will be handled by individual instructors.

Here's a link to the S13 235 midterm solutions (written up by Geri Jennings).

Here's a link to the S13 235 Mini-midterm2 solutions.

[Please continue to watch here for important developments and announcements!]

Rob was on leave at the Isaac Newton Institute for Mathematical Sciences for the Fall 2012 semester.

During Spring 2012, Rob is taught honors Differential Geometry of Curves & Surfaces (Math 563H). Here is the Spring 2012 ASCII file for Math 563H (Curves and Surfaces) topics & problems .

Rob also served as course chair for, and taught both (a double) section 4 and (a single) section 7 of Introduction to Linear Algebra (Math 235) in Spring 2012.

Here are notes on Inner Products, Gram-Schmidt and Ortho'matrices by Jenn Koonz (who gave a few lectures when Rob was in Germany at the end of March 2012) as well as notes on Determinants and on Eigenstuff by Arunas Rudvalis.

Here are links to Math 235 MiniMidtermII solutions (front) and (back) from Tuesday 17 April 2012.

And here are links to Math 235 Midterm solutions (page 1, 2, 3, 4, 5, and 6) from Wednesday 7 March 2012.

And links to Math 235 MiniMidtermI solutions (front) and (back) from Monday 13 February 2012.

In Fall 2011 Rob taught (a double) section 2 of Introduction to Linear Algebra (Math 235), with links to:

Fall 2011 Math 235 Practice Final Problems

Scanned pages of Fall Math 235 Common Midterm Solutions (find the sign error)!

Fall 2011 Math 235 Practice Midterm Problems.

Not as Ancient as You May Think...(Events of the Past Year Make Me "The Last Oak Standing Between Here and Eternity")

In Spring 2011, Rob taught the computational linear algebra (Math313/513-CS513) course while on sabbatical at Penn, and last fall he taught -- you guessed it! -- Introduction to Linear Algebra (Math 235) at UMass....

During Spring 2010, Rob taught honors Differential Geometry of Curves & Surfaces (Math 563H) and a double section of Linear Algebra (Math 235). Here is the ASCII file for Math 563H (Curves and Surfaces) topics & problems . (Andrew Reiter and Nicky Reyes are helping to TeX these now, so please stay tuned!)

Because he was the course chair during a semester when all the other instructors were graduate students, he and the other instructors established the following Math 235 (Linear Algebra) common guidelines, which may be useful to future course chairs.

Here's a link to the Fall 2009 Math 235 Practice Midterm and to sketches of answers! Here's a link to Fall 2009 Math 235 Midterm Answers. And here is a link to last year's Math 235 Practice Midterm. Finally, here's the Fall 2009 Math 235 practice final , along with Peter Norman's handwritten answers , a link to an old Math 235 practice final and links to older Math 235 practice finals or even older Math 235 practice finals, including one similar to our practice final with answers ....

Here are some Quick and Dirty Differential Equations notes prepared by Peter Norman last fall (with a little help from me) for use in Math 235.

During Spring 2009, Rob taught a special version of Math 462 (Geometry and the Imagination) - please visit here for the Math 462 topics and comments! He also taught a (double) section of Math 235 (Linear Algebra).

In Fall 2008, Rob taught a double-section of Math 235 (Linear Algebra).

Rob was on sabbatical in Spring 2008, but he taught back-to-back sections of Math 235 in Fall 2007 -- Linear Algebra is one of his favorite and most popular classes!

In Spring 2007 Rob taught Math 425 (Advanced Calculus) and a section of Math 235 (Linear Algebra). Here are links to the Math 425 (Advanced Calculus) homework schedule. Also, please have a look at my colleague Roman Federov's problems for enrichment and review. Rob organized the undergraduate TAP seminar (Math 191) during the Fall 2006 semester. It met in GANG (LGRT 1535) at lunchtime most Mondays and some Wednesdays. The following people kindly contributed to the 2006 TAP Topics. Many thanks to all of you!

In academic year 2006-07 Rob again planned to teach a two-semester course on Manifolds (Math 703-4) for graduate students. Due to unforeseen and unfortunate circumstances, Rob was not able to offer Math 704 in the spring. But here is where to find homework problems and informal notes for that course: Manifolds I (703) and Manifolds II (704), along with older notes from Fall 2002 (703), Spring 2003 (704) and Spring 2000 (Math 704).

In the Spring 2006 semester Rob taught Advanced Linear Algebra (Math 545) ; here are the updated problems/notes for this course. (Please compare with Rob's Spring 2002 advanced linear algebra problems/notes.) Rob also pinch-hit all semester for Ordinary Differential Equations (Math 331) in Spring 2006; here is the Math 331 general topics list and the Math 331 homework schedule for Rob's section. (This was an ambitious syllabus, covering more than the other sections did, and not without some ill-tempered jeers from the bleachers in the final innings -- it didn't help that Select Board meetings went on till after midnight on many, many occasions before this early morning course ;) In the Fall 2005 semester Rob taught Introduction to Abstract Algebra (Math 411); here are the notes and homework schedule .

In the Spring 2005 semester Rob was teaching an experimental version of Geometry and the Imagination. This was a very popular course, and Rob hopes to have the opportunity to offer it again soon, perhaps in conjunction with Math 563 (Differential Geometry of Curves and Surfaces)!

Rob was on sabbatical for 2003-04. During academic year 2002-03 Rob taught a two-semester course on Manifolds (Math 703-4) for graduate students. Here is where to find homework problems and notes from that course: Manifolds I (703) and Manifolds II (704), along with older notes from my Spring 2000 Math 704.

Rob has taught the basic graduate topology course several times, most recently in Fall 2000, Click here for the postscript or the rawtext version of the final Topology exam for Fall 2000.

And since this is Greek to me, here's a link to symbols like ε.

More

Watch here for further developments.

Address

        1435G Lederle Graduate Research Tower
        Department of Mathematics
        University of Massachusetts at Amherst
        Amherst MA 01003
        USA
   

Phone 413 545 6022

Secretary 413 545 2762

Fax 413 545 1801

Electronic Mail kusner "at" math "dot" umass "dot" edu

Department Webpage www.math.umass.edu/directory/faculty/rob-kusner

All material on this website is Copyleft* by Rob Kusner.