For fixed real number q > 0 consider the following system of equations:

Exam introduction to differentiable manifolds 1, 1-15-2019

Always motivate your answers and state the theorems/results you are using.

Question 1

For fixed real number q > 0 consider the following system of equations:

q

+ q

+ q

= 2q + q

−x

+ y

+ z

= q

a. Prove the following statement about the set S of solutions to the above equations: When q 6= 1, there is an open neighborhood U ⊂ R

of the point (1, 1, q) ∈ S such that U ∩ S is C

diffeomorphic to an open interval of R.

b. Formulate and prove a similar statement in the case q = 1.

Question 2

a. Explain how the formula ydx can be interpreted as a C

, 1-covector field ω on R

.

b. Express dω as a wedge product of two 1-covector fields.

c. Suppose γ : [0, 1] → R

is the 1-cube defined by γ(t) = (t, −(t − 1)t).

Calculate the integral R

γ

ω directly from the definition.

d. Calculate the integral R

γ

ω using Stokes theorem for 2-chains.

Question 3

a. Consider a metric g on open set P ⊂ R

and an isometry φ : P → P . If γ is a differentiable curve of minimal length between points p, q ∈ P , show that φ ◦ γ is also a differentiable curve of minimal length between φ(p), φ(q).

b. Find an element of Z ∈ Λ

(R

) such that Z ∧ Z 6= 0 and ?Z = Z with respect to the standard orientation and Euclidean metric.

Question 4

Consider the manifold M with atlas defined by charts M

= (0, 1) and M

= (1, 2) and M

= (0, 1) − {

} and M

= (1, 2) − {

} and transition map τ

: M

→ M

given by τ

(t) =

( t +

if t <

t +

if t >

.

a. What is the dimension of M ? and is M a C

manifold?

b. Give an atlas for the tangent bundle T M of M .

c. Write down an explicit example of a C

differentiable 2-covector field ω on T M that is not everywhere zero.

d. Can you find a function f : M → T M and find an ω as in part c. so that

f

ω is not everywhere zero?