<p>The sample copula of order <InlineEquation ID="IEq3"> <EquationSource Format="MATHML"><math> <mi>m</mi> </math></EquationSource> <EquationSource Format="TEX">$m$</EquationSource> </InlineEquation> provides an approximation to the copula that characterizes the dependence structure of a set of random variables. In this work, we first derive the sample copula of order <InlineEquation ID="IEq4"> <EquationSource Format="MATHML"><math> <mi>m</mi> </math></EquationSource> <EquationSource Format="TEX">$m$</EquationSource> </InlineEquation> for a random vector <InlineEquation ID="IEq5"> <EquationSource Format="MATHML"><math> <mi>X</mi> <mo>=</mo> <mo stretchy="false">(</mo> <msub> <mi>X</mi> <mn>1</mn> </msub> <mo>,</mo> <mo>…</mo> <mo>,</mo> <msub> <mi>X</mi> <mi>d</mi> </msub> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$X = (X_{1},\ldots ,X_{d})$</EquationSource> </InlineEquation>, with <InlineEquation ID="IEq6"> <EquationSource Format="MATHML"><math> <mi>d</mi> <mo>≥</mo> <mn>2</mn> </math></EquationSource> <EquationSource Format="TEX">$d \geq 2$</EquationSource> </InlineEquation>, by extending previously established results for the bivariate case. Based on the definition of a parametric copula with piecewise constant density, we show that the maximum likelihood estimation of the density parameters coincides with the elements employed in the definition of the sample copula of order <InlineEquation ID="IEq7"> <EquationSource Format="MATHML"><math> <mi>m</mi> </math></EquationSource> <EquationSource Format="TEX">$m$</EquationSource> </InlineEquation>, under the condition <InlineEquation ID="IEq8"> <EquationSource Format="MATHML"><math> <mn>2</mn> <mo>≤</mo> <mi>m</mi> <mo>≤</mo> <mi>n</mi> </math></EquationSource> <EquationSource Format="TEX">$2 \le m \le n$</EquationSource> </InlineEquation>, where <InlineEquation ID="IEq9"> <EquationSource Format="MATHML"><math> <mi>m</mi> </math></EquationSource> <EquationSource Format="TEX">$m$</EquationSource> </InlineEquation> is an integer divisor of <InlineEquation ID="IEq10"> <EquationSource Format="MATHML"><math> <mi>n</mi> </math></EquationSource> <EquationSource Format="TEX">$n$</EquationSource> </InlineEquation>, and <InlineEquation ID="IEq11"> <EquationSource Format="MATHML"><math> <mi>n</mi> </math></EquationSource> <EquationSource Format="TEX">$n$</EquationSource> </InlineEquation> denotes the given sample size. In the second part, we present an application of the sample copula of order <InlineEquation ID="IEq12"> <EquationSource Format="MATHML"><math> <mi>m</mi> </math></EquationSource> <EquationSource Format="TEX">$m$</EquationSource> </InlineEquation> as a complementary alternative for estimating the cosmological parameters <InlineEquation ID="IEq13"> <EquationSource Format="MATHML"><math> <msub> <mi>H</mi> <mn>0</mn> </msub> </math></EquationSource> <EquationSource Format="TEX">$H_{0}$</EquationSource> </InlineEquation> and <InlineEquation ID="IEq14"> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="normal">Ω</mi> <mrow> <mi>m</mi> <mn>0</mn> </mrow> </msub> </math></EquationSource> <EquationSource Format="TEX">$\Omega _{m0}$</EquationSource> </InlineEquation>, the current values of the Hubble constant and the matter density, respectively. This is carried out using a sample of observations of the redshift <InlineEquation ID="IEq15"> <EquationSource Format="MATHML"><math> <mi>z</mi> </math></EquationSource> <EquationSource Format="TEX">$z$</EquationSource> </InlineEquation>, the Hubble parameter <InlineEquation ID="IEq16"> <EquationSource Format="MATHML"><math> <mi>H</mi> </math></EquationSource> <EquationSource Format="TEX">$H$</EquationSource> </InlineEquation>, and its measurement error. To this end, several probability distributions, in addition to the Gaussian distribution, are proposed to model the observed error in the variable <InlineEquation ID="IEq17"> <EquationSource Format="MATHML"><math> <mi>H</mi> </math></EquationSource> <EquationSource Format="TEX">$H$</EquationSource> </InlineEquation>. Moreover, the applicability of this methodology is highlighted in the context of limited sample sizes.</p>

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Application of the sample copula of order \(m\) in the estimation of cosmological parameters

  • Ricardo Hoyos Argüelles

摘要

The sample copula of order m $m$ provides an approximation to the copula that characterizes the dependence structure of a set of random variables. In this work, we first derive the sample copula of order m $m$ for a random vector X = ( X 1 , , X d ) $X = (X_{1},\ldots ,X_{d})$ , with d 2 $d \geq 2$ , by extending previously established results for the bivariate case. Based on the definition of a parametric copula with piecewise constant density, we show that the maximum likelihood estimation of the density parameters coincides with the elements employed in the definition of the sample copula of order m $m$ , under the condition 2 m n $2 \le m \le n$ , where m $m$ is an integer divisor of n $n$ , and n $n$ denotes the given sample size. In the second part, we present an application of the sample copula of order m $m$ as a complementary alternative for estimating the cosmological parameters H 0 $H_{0}$ and Ω m 0 $\Omega _{m0}$ , the current values of the Hubble constant and the matter density, respectively. This is carried out using a sample of observations of the redshift z $z$ , the Hubble parameter H $H$ , and its measurement error. To this end, several probability distributions, in addition to the Gaussian distribution, are proposed to model the observed error in the variable H $H$ . Moreover, the applicability of this methodology is highlighted in the context of limited sample sizes.