T2: The Exponential Map Flashcards

1
Q

Define the norm of an object

A

A function from k-vector space to +ve which defines a notion of length

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2
Q

Define the Jordan Cannonical form

A

Where a matrix can be expressed as an upper triangular matrix containing blocks along the diagonal. Each block is upper triangular with non-zero terms along the diagonal and ones along the super diagonal.

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3
Q

In what case is a Jordan cannonical form a diagonal matrix?

A

Where all the blocks have size 1

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4
Q

Under what criteria is the exponential map surjective?`

A

Over the complex domain

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5
Q

Define a one-parameter subgroup

A

A differentiable map from real numbers under addition, to the group GL_n(K). Equivalently, a group homomorphism between these groups.

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6
Q

What is the sufficient condition for f to be a one-parameter subgroup?

A

It is continuous and exists over some integral 0 to a.

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7
Q

Define the exponential map exp(X)

A

For X∈ gl_n (K), sum from 0 to infty X^k/k!

Gothic

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8
Q

Under what condition does exp(X+Y) = exp(X)exp(Y)

A

If X and Y commutes

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9
Q

Where is the exponential map uniformly convergent?

A

Over compact subsets of gl_n(K)

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10
Q

exp(sX) exp(tX) = ?

A

exp((s+t)X)

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11
Q

g exp(X) g^−1 = ?

A

exp(gXg^-1)

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12
Q

exp(tr(X)) = ?

A

det exp(X)

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13
Q

d/dt det(exp(tX)) at t=0 = ?

A

tr(X)

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14
Q

Define gl_n (K) (gothic)

A

= M_n(K) : the set of n x n matrices over K

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15
Q

Define the map t → exp(tX)

A

Map from reals to to GL_n(K)

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16
Q

d/dt [exp(tX)] = ?

A

X exp(tX)

17
Q

What does it mean for the exponential map to be a local diffeomorphism?

A

There exists a small region U0 ⊂ gl_n(K) containing 0 and V0 ⊂ GL_n(K) containing I such that the exp map is a diffeomorphism

18
Q

State the easy BCH formula exp(tX)exp(tY)

A

exp[t(X+Y) + t^2(XY-YX) + O(t^3)]

19
Q

What expression characterises a one-parameter subgroup?

A

f(s+t) = f(s)f(t) for all s,t in reals

20
Q

exp(trX) = ?

A

det exp(X)