Let's denote by $C$ the space of continuous functions $[0,T] \rightarrow \mathbb{R}^n$ for some fixed $T>0$ and assume we have a probability measure $Q$ on the space $C$. Consider the evaluation functions $e_t : C \rightarrow \mathbb{R}^n$ given by $e_t(\alpha) = \alpha(t)$. We can then define a family of marginals (not sure if it's the right word in this context) of $Q$ as probability measures on $\mathbb{R}^n$ given as push-forwards of $Q$ by $e_t$, i.e. $$ \rho_t := e_t {}_{\#} Q \ldotp$$ Let's assume that we've shown that the $\rho_t$'s are absolutely continuous with respect to the standard Lebesgue measure. Can we somehow reconstruct $Q$ knowing only the distributions $\rho_t$? in particular, can we rewrite integrals of the form $$\int_C \int_0^T f(t,\gamma(t))dt dQ$$ as something like $$\int_0^T \int_{\mathbb{R}^n} f(t,x) \rho_t(x) dx dt \quad ?$$ Assuming $f$ is at least nice enough to apply Fubini, say positive. Basically I'm interested in what can we say about the family $\{ \rho_t\}$ and vice-versa what can we say about $Q$ knowing that its marginals have densities wrt the Lebesgue measure. Can we for example say that the function $$\rho(t,x) := \rho_t(x)$$ is, at least, measurable? Here $\rho_t(x)$ denotes the density of the measure $\rho_t$ at point $x$.
2026-03-27 21:05:22.1774645522
Reconstructing a measure from its (absolutely continuous) marginals
55 Views Asked by Bumbble Comm https://math.techqa.club/user/bumbble-comm/detail AtRelated Questions in ANALYSIS
- Analytical solution of a nonlinear ordinary differential equation
- Finding radius of convergence $\sum _{n=0}^{}(2+(-1)^n)^nz^n$
- Show that $d:\mathbb{C}\times\mathbb{C}\rightarrow[0,\infty[$ is a metric on $\mathbb{C}$.
- conformal mapping and rational function
- What are the functions satisfying $f\left(2\sum_{i=0}^{\infty}\frac{a_i}{3^i}\right)=\sum_{i=0}^{\infty}\frac{a_i}{2^i}$
- Proving whether function-series $f_n(x) = \frac{(-1)^nx}n$
- Elementary question on continuity and locally square integrability of a function
- Proving smoothness for a sequence of functions.
- How to prove that $E_P(\frac{dQ}{dP}|\mathcal{G})$ is not equal to $0$
- Integral of ratio of polynomial
Related Questions in MEASURE-THEORY
- On sufficient condition for pre-compactness "in measure"(i.e. in Young measure space)
- Absolutely continuous functions are dense in $L^1$
- I can't undestand why $ \{x \in X : f(x) > g(x) \} = \bigcup_{r \in \mathbb{Q}}{\{x\in X : f(x) > r\}\cap\{x\in X:g(x) < r\}} $
- Trace $\sigma$-algebra of a product $\sigma$-algebra is product $\sigma$-algebra of the trace $\sigma$-algebras
- Meaning of a double integral
- Random variables coincide
- Convergence in measure preserves measurability
- Convergence in distribution of a discretized random variable and generated sigma-algebras
- A sequence of absolutely continuous functions whose derivatives converge to $0$ a.e
- $f\in L_{p_1}\cap L_{p_2}$ implies $f\in L_{p}$ for all $p\in (p_1,p_2)$
Related Questions in LEBESGUE-INTEGRAL
- A sequence of absolutely continuous functions whose derivatives converge to $0$ a.e
- Square Integrable Functions are Measurable?
- Lebesgue measure and limit of the integral.
- Solving an integral by using the Dominated Convergence Theorem.
- Convergence of a seqence under the integral sign
- If $g \in L^1$ and $f_n \to f$ a.e. where $|f_n| \leq 1$, then $g*f_n \to g*f$ uniformly on each compact set.
- Integral with Dirac measure.
- If $u \in \mathscr{L}^1(\lambda^n), v\in \mathscr{L}^\infty (\lambda^n)$, then $u \star v$ is bounded and continuous.
- Proof that $x \mapsto \int |u(x+y)-u(y)|^p \lambda^n(dy)$ is continuous
- a) Compute $T(1_{[\alpha,\beta]})$ for all $0<\alpha <\beta<0$
Related Questions in GEOMETRIC-MEASURE-THEORY
- Lipschitz continuous function whose derivative is not continuous almost everywhere
- Relative volume of $\delta$-fattening (neighborhood) of a compact set
- Surface Area in $R^n$
- Excess of Caccioppoli sets
- What type of measure is this?
- Lipschitz extension of affine function to whole space
- Is it true $\mu (A+B) = \mu (A) + \mu(B) $ for bounded sets $ A, B \subset R $
- The Lebesgue measure as energy minimizer?
- Caratheodory's construction
- Upper Bounding Hausdorff Measure
Trending Questions
- Induction on the number of equations
- How to convince a math teacher of this simple and obvious fact?
- Find $E[XY|Y+Z=1 ]$
- Refuting the Anti-Cantor Cranks
- What are imaginary numbers?
- Determine the adjoint of $\tilde Q(x)$ for $\tilde Q(x)u:=(Qu)(x)$ where $Q:U→L^2(Ω,ℝ^d$ is a Hilbert-Schmidt operator and $U$ is a Hilbert space
- Why does this innovative method of subtraction from a third grader always work?
- How do we know that the number $1$ is not equal to the number $-1$?
- What are the Implications of having VΩ as a model for a theory?
- Defining a Galois Field based on primitive element versus polynomial?
- Can't find the relationship between two columns of numbers. Please Help
- Is computer science a branch of mathematics?
- Is there a bijection of $\mathbb{R}^n$ with itself such that the forward map is connected but the inverse is not?
- Identification of a quadrilateral as a trapezoid, rectangle, or square
- Generator of inertia group in function field extension
Popular # Hahtags
second-order-logic
numerical-methods
puzzle
logic
probability
number-theory
winding-number
real-analysis
integration
calculus
complex-analysis
sequences-and-series
proof-writing
set-theory
functions
homotopy-theory
elementary-number-theory
ordinary-differential-equations
circles
derivatives
game-theory
definite-integrals
elementary-set-theory
limits
multivariable-calculus
geometry
algebraic-number-theory
proof-verification
partial-derivative
algebra-precalculus
Popular Questions
- What is the integral of 1/x?
- How many squares actually ARE in this picture? Is this a trick question with no right answer?
- Is a matrix multiplied with its transpose something special?
- What is the difference between independent and mutually exclusive events?
- Visually stunning math concepts which are easy to explain
- taylor series of $\ln(1+x)$?
- How to tell if a set of vectors spans a space?
- Calculus question taking derivative to find horizontal tangent line
- How to determine if a function is one-to-one?
- Determine if vectors are linearly independent
- What does it mean to have a determinant equal to zero?
- Is this Batman equation for real?
- How to find perpendicular vector to another vector?
- How to find mean and median from histogram
- How many sides does a circle have?