Norms in Finite Dimensional Spaces
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Questions and Answers

What is the relation of all norms over a finite dimensional vector space X?

  • Norms are independent of each other.
  • Norms can vary significantly.
  • All norms are equivalent. (correct)
  • Only one norm can exist.
  • The proposition states that the 1-norm is less than or equal to the norm N2 in every case.

    False

    What is the formula for the norm of a vector x in Rd as defined in the content?

    kxk1 = Σ|xi| for i=1 to d

    In the mapping Φ: X → Rd, x is represented as _____ in terms of the basis {e1,..., ed}.

    <p>x = Σ xi ei</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>C0 = Positive constant related to N1 C1 = Upper bound for N1 C00 = Positive constant related to N2 C10 = Upper bound for N2</p> Signup and view all the answers

    What does the normalization of vector x refer to in the context?

    <p>Scaling the vector to lie on the unit sphere S1</p> Signup and view all the answers

    The mapping Φ is not continuous.

    <p>False</p> Signup and view all the answers

    Describe what is established when applying the previous proposition to (X, N1).

    <p>It establishes the existence of positive constants bounding N1 in relation to kxk1.</p> Signup and view all the answers

    What is the supremum norm defined as in normed space X = C1([0, 1])?

    <p>The supremum of the absolute value of the function itself</p> Signup and view all the answers

    If K is a compact subset of a normed space, then K must also be bounded.

    <p>True</p> Signup and view all the answers

    What does it mean for a subset K of a normed space to be compact?

    <p>Every sequence in K contains a convergent subsequence that converges to an element within K.</p> Signup and view all the answers

    A compact set is always _____.

    <p>closed</p> Signup and view all the answers

    Match the following concepts with their definitions:

    <p>Compact set = A set in a normed space where every sequence has a convergent subsequence Supremum norm = The maximum absolute value of a function over an interval Closed set = A set containing all its limit points Bounded set = A set where all elements are within a finite distance from the origin</p> Signup and view all the answers

    Which of the following statements is true about the supremum of a sequence in a compact set?

    <p>The supremum must exist and be finite</p> Signup and view all the answers

    All closed sets in a normed space are compact.

    <p>False</p> Signup and view all the answers

    Can you provide an example of a compact set in R?

    <p>[a, b] for any real numbers a and b with a ≤ b.</p> Signup and view all the answers

    What characterizes a series in a normed space as being convergent?

    <p>There exists an element x in the space such that the limit of the norm of the difference between the partial sums and x is zero.</p> Signup and view all the answers

    In a Banach space, any absolutely convergent series is also convergent.

    <p>True</p> Signup and view all the answers

    Define an absolutely convergent series.

    <p>A series is absolutely convergent if the sum of the norms of its terms is finite.</p> Signup and view all the answers

    The partial sums of the series are defined as sN = _____ for N ∈ N.

    <p>∑_{n=1}^{N} x_n</p> Signup and view all the answers

    What is necessary to prove that a sequence is a Cauchy sequence in a Banach space?

    <p>The norms of the differences between its elements must approach zero.</p> Signup and view all the answers

    Every sequence in a Banach space is automatically Cauchy.

    <p>False</p> Signup and view all the answers

    What does it mean for a Banach space to be complete?

    <p>A Banach space is complete if every Cauchy sequence in the space converges to an element within that space.</p> Signup and view all the answers

    Which of the following is NOT a property of a K-vector space?

    <p>Existence of a multiplicative identity</p> Signup and view all the answers

    A seminorm on a vector space must ensure that N(x) is always greater than or equal to zero.

    <p>True</p> Signup and view all the answers

    What is the term for a function N: X → R that satisfies the properties of nonnegativity, homogeneity, and the triangle inequality?

    <p>seminorm</p> Signup and view all the answers

    For any vectors x, y in a K-vector space, the property that states N(x+y) ≤ N(x) + N(y) is referred to as the __________ inequality.

    <p>Triangle</p> Signup and view all the answers

    Match the following properties with their definitions:

    <p>Commutativity = x + y = y + x Associativity of addition = (x + y) + z = x + (y + z) Existence of zero vector = 0X + x = x Homogeneity = N(αx) = |α|N(x)</p> Signup and view all the answers

    What is always true for a norm but may not be true for a seminorm?

    <p>Existence of a non-zero vector with zero norm</p> Signup and view all the answers

    What symbol represents the additive identity element in a K-vector space?

    <p>0X</p> Signup and view all the answers

    What is the relationship between the spaces Lq and `q?

    <p>Lq can be identified with `q when S = N.</p> Signup and view all the answers

    The properties of scalar multiplication in a K-vector space include that 1x = x for all x in the space.

    <p>True</p> Signup and view all the answers

    The sequence space `1 (N) is equivalent to the space L1 (S, µ) for some special choice of S and µ.

    <p>True</p> Signup and view all the answers

    What does the notation kXkq represent?

    <p>The norm in Lq space for the function X.</p> Signup and view all the answers

    `p (N) is defined as the set of sequences x = (xn) such that the sum of |xn|^p is ___ for n from 1 to infinity.

    <p>finite</p> Signup and view all the answers

    If µ(S) < ∞, which measure space configuration is valid?

    <p>The propositions about `p (N) hold.</p> Signup and view all the answers

    The counting measure can only be used for finite sets.

    <p>False</p> Signup and view all the answers

    In the definition of `p (N), the symbol p is required to be greater than ___ for the space to be normed.

    <p>1</p> Signup and view all the answers

    In the context of continuous functions, what does it mean if $\int_a^b |f(t)|dt = 0$?

    <p>f(t) equals zero for all t in [a, b]</p> Signup and view all the answers

    The function space C(I) includes only functions that are differentiable but not necessarily continuously differentiable.

    <p>False</p> Signup and view all the answers

    What is the definition of a normed space?

    <p>A normed space is a vector space equipped with a function called a norm, which assigns a length to each vector.</p> Signup and view all the answers

    The open ball centered at $x_0$ with radius $r$ is defined as $B(x_0, r) = { x \in X ; kx - x_0 k < r }$ while the closed ball is defined as $B_c(x_0, r) = { x \in X ; kx - x_0 k \underline{______} r }$

    <p>≤</p> Signup and view all the answers

    Match the following definitions with their corresponding terms:

    <p>C(I) = Space of continuously differentiable functions Norm = Function assigning lengths to vectors Open Set = Contains all points with a given radius around its members Closed Set = Complement of an open set</p> Signup and view all the answers

    Which of the following properties is NOT satisfied by a semi-norm?

    <p>It guarantees the uniqueness of zero vector only.</p> Signup and view all the answers

    The integral of a continuous function is always nonnegative.

    <p>False</p> Signup and view all the answers

    What is the significance of the sup norm in function spaces?

    <p>The sup norm measures the maximum absolute value of a function and its derivative over a specified interval.</p> Signup and view all the answers

    Study Notes

    Lecture Notes for Master's Degree in Stochastics and Data Sciences

    • Course covered: Analysis
    • Academic Year: 2024-2025
    • Instructor: Bertrand Lods
    • Original lectures from 2015-2016, with updates for 2024-2025

    Contents

    • Normed spaces: the norm and its properties, topology of normed spaces, equivalent norms, product spaces, continuity of functions, fundamental examples like Lebesgue spaces (L¹), LP-spaces (1 ≤ p ≤ 8), space of linear applications, compactness, and finite-dimensional spaces
    • Banach spaces: Cauchy sequences, completeness, examples, fundamental properties of Banach spaces, problems, complements involving compact operators
    • Inner product spaces and Hilbert spaces: Definitions, general properties, Hilbert spaces, projection theorem, orthogonal complements, orthonormal families, Hilbert bases, and more properties of the dual space/Hahn-Banach Theorem
    • Complements about Lebesgue spaces: Useful inequalities (Jensen, Minkowski), integral depending on a parameter, convolution
    • Fourier analysis: Fourier transform in L¹(Rd), main properties, Riemann-Lebesgue theorem, inversion formula
    • Laplace transform: definition, linearity, continuity, initial and final value theorems

    Additional Information

    • Proofs that students need to prepare and understand are indicated in the margins with a symbol.
    • Lecture notes were created with support from the project: "Start up of the Master's Degree in Stochastics and Data Science."

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    Description

    Explore the relationships and properties of norms in finite dimensional vector spaces through this comprehensive quiz. Test your understanding of various norms, compactness, and continuity in normed spaces. The quiz includes matching terms, definitions, and true or false statements related to norms.

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