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4.1] for an overview and further references. 16.1]. This happens if \(X_{0}\) is sufficiently close to \({\overline{x}}\), say within a distance \(\rho'>0\). (x-a)+ \frac{f''(a)}{2!} Narrowing the domain can often be done through the use of various addition or scaling formulas for the function being approximated. Then the law under \(\overline{\mathbb {P}}\) of \((W,Y,Z)\) equals the law of \((W^{1},Y^{1},Z^{1})\), and the law under \(\overline{\mathbb {P}}\) of \((W,Y,Z')\) equals the law of \((W^{2},Y^{2},Z^{2})\). Let It also implies that \(\widehat{\mathcal {G}}\) satisfies the positive maximum principle as a linear operator on \(C_{0}(E_{0})\). , essentially different from geometric Brownian motion, such that all joint moments of all finite-dimensional marginal distributions. be a The coefficient in front of \(x_{i}^{2}\) on the left-hand side is \(-\alpha_{ii}+\phi_{i}\) (recall that \(\psi_{(i),i}=0\)), which therefore is zero. The least-squares method was published in 1805 by Legendreand in 1809 by Gauss. where the MoorePenrose inverse is understood. . The following two examples show that the assumptions of LemmaA.1 are tight in the sense that the gap between (i) and (ii) cannot be closed. \(Y^{1}\), \(Y^{2}\) Mathematically, a CRC can be described as treating a binary data word as a polynomial over GF(2) (i.e., with each polynomial coefficient being zero or one) and per-forming polynomial division by a generator polynomial G(x). \(d\)-dimensional It process satisfying Note that unlike many other results in that paper, Proposition2 in Bakry and mery [4] does not require \(\widehat{\mathcal {G}}\) to leave \(C^{\infty}_{c}(E_{0})\) invariant, and is thus applicable in our setting. be two The 9 term would technically be multiplied to x^0 . 131, 475505 (2006), Hajek, B.: Mean stochastic comparison of diffusions. This proves(i). Let are continuous processes, and The use of financial polynomials is used in the real world all the time. In particular, if \(i\in I\), then \(b_{i}(x)\) cannot depend on \(x_{J}\). In financial planning, polynomials are used to calculate interest rate problems that determine how much money a person accumulates after a given number of years with a specified initial investment. : Hankel transforms associated to finite reflection groups. Soc., Ser. $$, \(X_{t} = A_{t} + \mathrm{e} ^{-\beta(T-t)}Y_{t} \), $$ A_{t} = \mathrm{e}^{\beta t} X_{0}+\int_{0}^{t} \mathrm{e}^{\beta(t- s)}b ds $$, $$ Y_{t}= \int_{0}^{t} \mathrm{e}^{\beta(T- s)}\sigma(X_{s}) dW_{s} = \int_{0}^{t} \sigma^{Y}_{s} dW_{s}, $$, \(\sigma^{Y}_{t} = \mathrm{e}^{\beta(T- t)}\sigma(A_{t} + \mathrm{e}^{-\beta (T-t)}Y_{t} )\), $$ \|\sigma^{Y}_{t}\|^{2} \le C_{Y}(1+\| Y_{t}\|) $$, $$ \nabla\|y\| = \frac{y}{\|y\|} \qquad\text{and}\qquad\frac {\partial^{2} \|y\|}{\partial y_{i}\partial y_{j}}= \textstyle\begin{cases} \frac{1}{\|y\|}-\frac{1}{2}\frac{y_{i}^{2}}{\|y\|^{3}}, & i=j,\\ -\frac{1}{2}\frac{y_{i} y_{j}}{\|y\|^{3}},& i\neq j. $$, \(2 {\mathcal {G}}p({\overline{x}}) < (1-2\delta) h({\overline{x}})^{\top}\nabla p({\overline{x}})\), $$ 2 {\mathcal {G}}p \le\left(1-\delta\right) h^{\top}\nabla p \quad\text{and}\quad h^{\top}\nabla p >0 \qquad\text{on } E\cap U. $$, $$\begin{aligned} Y_{t} &= y_{0} + \int_{0}^{t} b_{Y}(Y_{s}){\,\mathrm{d}} s + \int_{0}^{t} \sigma_{Y}(Y_{s}){\,\mathrm{d}} W_{s}, \\ Z_{t} &= z_{0} + \int_{0}^{t} b_{Z}(Y_{s},Z_{s}){\,\mathrm{d}} s + \int_{0}^{t} \sigma _{Z}(Y_{s},Z_{s}){\,\mathrm{d}} W_{s}, \\ Z'_{t} &= z_{0} + \int_{0}^{t} b_{Z}(Y_{s},Z'_{s}){\,\mathrm{d}} s + \int_{0}^{t} \sigma _{Z}(Y_{s},Z'_{s}){\,\mathrm{d}} W_{s}. is a Brownian motion. J. Multivar. Let Contemp. \(y\in E_{Y}\). A Taylor series approximation uses a Taylor series to represent a number as a polynomial that has a very similar value to the number in a neighborhood around a specified \(x\) value: \[f(x) = f(a)+\frac {f'(a)}{1!} Animated Video created using Animaker - https://www.animaker.com polynomials(draft) J. Stat. The proof of Theorem5.7 is divided into three parts. $$, $$ \int_{-\infty}^{\infty}\frac{1}{y}{\boldsymbol{1}_{\{y>0\}}}L^{y}_{t}{\,\mathrm{d}} y = \int_{0}^{t} \frac {\nabla p^{\top}\widehat{a} \nabla p(X_{s})}{p(X_{s})}{\boldsymbol{1}_{\{ p(X_{s})>0\}}}{\,\mathrm{d}} s. $$, \((\nabla p^{\top}\widehat{a} \nabla p)/p\), $$ a \nabla p = h p \qquad\text{on } M. $$, \(\lambda_{i} S_{i}^{\top}\nabla p = S_{i}^{\top}a \nabla p = S_{i}^{\top}h p\), \(\lambda_{i}(S_{i}^{\top}\nabla p)^{2} = S_{i}^{\top}\nabla p S_{i}^{\top}h p\), $$ \nabla p^{\top}\widehat{a} \nabla p = \nabla p^{\top}S\varLambda^{+} S^{\top}\nabla p = \sum_{i} \lambda_{i}{\boldsymbol{1}_{\{\lambda_{i}>0\}}}(S_{i}^{\top}\nabla p)^{2} = \sum_{i} {\boldsymbol{1}_{\{\lambda_{i}>0\}}}S_{i}^{\top}\nabla p S_{i}^{\top}h p. $$, $$ \nabla p^{\top}\widehat{a} \nabla p \le|p| \sum_{i} \|S_{i}\|^{2} \|\nabla p\| \|h\|. Math. The other is x3 + x2 + 1. Aerospace, civil, environmental, industrial, mechanical, chemical, and electrical engineers are all based on polynomials (White). such that 13, 430433 (1942), Da Prato, G., Frankowska, H.: Invariance of stochastic control systems with deterministic arguments. Swiss Finance Institute Research Paper No. \(V\), denoted by \({\mathcal {I}}(V)\), is the set of all polynomials that vanish on \(V\). $$, $$ Z_{u} = p(X_{0}) + (2-2\delta)u + 2\int_{0}^{u} \sqrt{Z_{v}}{\,\mathrm{d}}\beta_{v}. \end{aligned}$$, $$ { \vec{p} }^{\top}F(u) = { \vec{p} }^{\top}H(X_{t}) + { \vec{p} }^{\top}G^{\top}\int_{t}^{u} F(s) {\,\mathrm{d}} s, \qquad t\le u\le T, $$, \(F(u) = {\mathbb {E}}[H(X_{u}) \,|\,{\mathcal {F}}_{t}]\), \(F(u)=\mathrm{e}^{(u-t)G^{\top}}H(X_{t})\), $$ {\mathbb {E}}[p(X_{T}) \,|\, {\mathcal {F}}_{t} ] = F(T)^{\top}\vec{p} = H(X_{t})^{\top}\mathrm{e} ^{(T-t)G} \vec{p}, $$, $$ dX_{t} = (b+\beta X_{t})dt + \sigma(X_{t}) dW_{t}, $$, $$ \|\sigma(X_{t})\|^{2} \le C(1+\|X_{t}\|) \qquad \textit{for all }t\ge0 $$, $$ {\mathbb {E}}\big[ \mathrm{e}^{\delta\|X_{0}\|}\big]< \infty \qquad \textit{for some } \delta>0, $$, $$ {\mathbb {E}}\big[\mathrm{e}^{\varepsilon\|X_{T}\|}\big]< \infty. MATH be a This can be very useful for modeling and rendering objects, and for doing mathematical calculations on their edges and surfaces. The simple polynomials used are x, x 2, , x k. We can obtain orthogonal polynomials as linear combinations of these simple polynomials. 30, 605641 (2012), Stieltjes, T.J.: Recherches sur les fractions continues. Mar 16, 2020 A polynomial of degree d is a vector of d + 1 coefficients: = [0, 1, 2, , d] For example, = [1, 10, 9] is a degree 2 polynomial. $$, \(h_{ij}(x)=-\alpha_{ij}x_{i}+(1-{\mathbf{1}}^{\top}x)\gamma_{ij}\), $$ a_{ii}(x) = -\alpha_{ii}x_{i}^{2} + x_{i}(\phi_{i} + \psi_{(i)}^{\top}x) + (1-{\mathbf{1}} ^{\top}x) g_{ii}(x) $$, \(a(x){\mathbf{1}}=(1-{\mathbf{1}}^{\top}x)f(x)\), \(f_{i}\in{\mathrm {Pol}}_{1}({\mathbb {R}}^{d})\), $$ \begin{aligned} x_{i}\bigg( -\sum_{j=1}^{d} \alpha_{ij}x_{j} + \phi_{i} + \psi_{(i)}^{\top}x\bigg) &= (1 - {\mathbf{1}}^{\top}x)\big(f_{i}(x) - g_{ii}(x)\big) \\ &= (1 - {\mathbf{1}}^{\top}x)\big(\eta_{i} + ({\mathrm {H}}x)_{i}\big) \end{aligned} $$, \({\mathrm {H}} \in{\mathbb {R}}^{d\times d}\), \(x_{i}\phi_{i} = \lim_{s\to0} s^{-1}\eta_{i} + ({\mathrm {H}}x)_{i}\), $$ x_{i}\bigg(- \sum_{j=1}^{d} \alpha_{ij}x_{j} + \psi_{(i)}^{\top}x + \phi _{i} {\mathbf{1}} ^{\top}x\bigg) = 0 $$, \(x_{i} \sum_{j\ne i} (-\alpha _{ij}+\psi _{(i),j}+\alpha_{ii})x_{j} = 0\), \(\psi _{(i),j}=\alpha_{ij}-\alpha_{ii}\), $$ a_{ii}(x) = -\alpha_{ii}x_{i}^{2} + x_{i}\bigg(\alpha_{ii} + \sum_{j\ne i}(\alpha_{ij}-\alpha_{ii})x_{j}\bigg) = \alpha_{ii}x_{i}(1-{\mathbf {1}}^{\top}x) + \sum_{j\ne i}\alpha_{ij}x_{i}x_{j} $$, $$ a_{ii}(x) = x_{i} \sum_{j\ne i}\alpha_{ij}x_{j} = x_{i}\bigg(\alpha_{ik}s + \frac{1-s}{d-1}\sum_{j\ne i,k}\alpha_{ij}\bigg). Fac. Thus if we can show that \(T\) is surjective, the rank-nullity theorem \(\dim(\ker T) + \dim(\mathrm{range } T) = \dim{\mathcal {X}} \) implies that \(\ker T\) is trivial. Since \(h^{\top}\nabla p(X_{t})>0\) on \([0,\tau(U))\), the process \(A\) is strictly increasing there. . and the remaining entries zero. In: Azma, J., et al. The first part of the proof applied to the stopped process \(Z^{\sigma}\) under yields \((\mu_{0}-\phi \nu_{0}){\boldsymbol{1}_{\{\sigma>0\}}}\ge0\) for all \(\phi\in {\mathbb {R}}\). Google Scholar, Forman, J.L., Srensen, M.: The Pearson diffusions: a class of statistically tractable diffusion processes. \({\mathbb {P}}_{z}\) \end{aligned}$$, $$ {\mathbb {E}}\left[ Z^{-}_{\tau}{\boldsymbol{1}_{\{\rho< \infty\}}}\right] = {\mathbb {E}}\left[ - \int _{0}^{\tau}{\boldsymbol{1}_{\{Z_{s}\le0\}}}\mu_{s}{\,\mathrm{d}} s {\boldsymbol{1}_{\{\rho < \infty\}}}\right]. For instance, a polynomial equation can be used to figure the amount of interest that will accrue for an initial deposit amount in an investment or savings account at a given interest rate. Polynomial regression models are usually fit using the method of least squares. The generator polynomial will be called a CRC poly- Probably the most important application of Taylor series is to use their partial sums to approximate functions . Notice the cascade here, knowing x 0 = i p c a, we can solve for x 1 (we don't actually need x 0 to nd x 1 in the current case, but in general, we have a is well defined and finite for all \(t\ge0\), with total variation process \(V\). For any \(q\in{\mathcal {Q}}\), we have \(q=0\) on \(M\) by definition, whence, or equivalently, \(S_{i}(x)^{\top}\nabla^{2} q(x) S_{i}(x) = -\nabla q(x)^{\top}\gamma_{i}'(0)\). . . Available at SSRN http://ssrn.com/abstract=2397898, Filipovi, D., Tappe, S., Teichmann, J.: Invariant manifolds with boundary for jump-diffusions. Uniqueness of polynomial diffusions is established via moment determinacy in combination with pathwise uniqueness. Camb. 25, 392393 (1963), Horn, R.A., Johnson, C.A. LemmaE.3 implies that \(\widehat {\mathcal {G}} \) is a well-defined linear operator on \(C_{0}(E_{0})\) with domain \(C^{\infty}_{c}(E_{0})\). \(\tau _{0}=\inf\{t\ge0:Z_{t}=0\}\) 29, 483493 (1976), Ethier, S.N., Kurtz, T.G. But all these elements can be realized as \((TK)(x)=K(x)Qx\) as follows: If \(i,j,k\) are all distinct, one may take, and all remaining entries of \(K(x)\) equal to zero. As an example, take the polynomial 4x^3 + 3x + 9. MathSciNet Then \(-Z^{\rho_{n}}\) is a supermartingale on the stochastic interval \([0,\tau)\), bounded from below.Footnote 4 Thus by the supermartingale convergence theorem, \(\lim_{t\uparrow\tau}Z_{t\wedge\rho_{n}}\) exists in , which implies \(\tau\ge\rho_{n}\). To this end, define, We claim that \(V_{t}<\infty\) for all \(t\ge0\). Econ. For any \(p\in{\mathrm{Pol}}_{n}(E)\), Its formula yields, The quadratic variation of the right-hand side satisfies, for some constant \(C\). where \(\widehat{b}_{Y}(y)=b_{Y}(y){\mathbf{1}}_{E_{Y}}(y)\) and \(\widehat{\sigma}_{Y}(y)=\sigma_{Y}(y){\mathbf{1}}_{E_{Y}}(y)\). Substituting into(I.2) and rearranging yields, for all \(x\in{\mathbb {R}}^{d}\). Then(3.1) and(3.2) in conjunction with the linearity of the expectation and integration operators yield, Fubinis theorem, justified by LemmaB.1, yields, where we define \(F(u) = {\mathbb {E}}[H(X_{u}) \,|\,{\mathcal {F}}_{t}]\). with representation, where To prove that \(X\) is non-explosive, let \(Z_{t}=1+\|X_{t}\|^{2}\) for \(t<\tau\), and observe that the linear growth condition(E.3) in conjunction with Its formula yields \(Z_{t} \le Z_{0} + C\int_{0}^{t} Z_{s}{\,\mathrm{d}} s + N_{t}\) for all \(t<\tau\), where \(C>0\) is a constant and \(N\) a local martingale on \([0,\tau)\). J. Econom. It thus becomes natural to pose the following question: Can one find a process The proof of Part(ii) involves the same ideas as used for instance in Spreij and Veerman [44, Proposition3.1]. scalable. Math. \end{cases} $$, $$ \nabla f(y)= \frac{1}{2\sqrt{1+\|y\|}}\frac{ y}{\|y\|} $$, $$ \frac{\partial^{2} f(y)}{\partial y_{i}\partial y_{j}}=-\frac{1}{4\sqrt {1+\| y\|}^{3}}\frac{ y_{i}}{\|y\|}\frac{ y}{\|y\|}+\frac{1}{2\sqrt{1+\|y\| }}\times \textstyle\begin{cases} \frac{1}{\|y\|}-\frac{1}{2}\frac{y_{i}^{2}}{\|y\|^{3}}, & i=j\\ -\frac{1}{2}\frac{y_{i} y_{j}}{\|y\|^{3}},& i\neq j \end{cases} $$, $$ dZ_{t} = \mu^{Z}_{t} dt +\sigma^{Z}_{t} dW_{t} $$, $$ \mu^{Z}_{t} = \frac{1}{2}\sum_{i,j=1}^{d} \frac{\partial^{2} f(Y_{t})}{\partial y_{i}\partial y_{j}} (\sigma^{Y}_{t}{\sigma^{Y}_{t}}^{\top})_{ij},\qquad\sigma ^{Z}_{t}= \nabla f(Y_{t})^{\top}\sigma^{Y}_{t}. Now let \(f(y)\) be a real-valued and positive smooth function on \({\mathbb {R}}^{d}\) satisfying \(f(y)=\sqrt{1+\|y\|}\) for \(\|y\|>1\). Next, it is straightforward to verify that (i) and (ii) imply (A0)(A2), so we focus on the converse direction and assume(A0)(A2) hold. To this end, let \(a=S\varLambda S^{\top}\) be the spectral decomposition of \(a\), so that the columns \(S_{i}\) of \(S\) constitute an orthonormal basis of eigenvectors of \(a\) and the diagonal elements \(\lambda_{i}\) of \(\varLambda \) are the corresponding eigenvalues. Indeed, \(X\) has left limits on \(\{\tau<\infty\}\) by LemmaE.4, and \(E_{0}\) is a neighborhood in \(M\) of the closed set \(E\). The growth condition yields, for \(t\le c_{2}\), and Gronwalls lemma then gives \({\mathbb {E}}[ \sup _{s\le t\wedge \tau_{n}}\|Y_{s}-Y_{0}\|^{2}] \le c_{3}t \mathrm{e}^{4c_{2}\kappa t}\), where \(c_{3}=4c_{2}\kappa(1+{\mathbb {E}}[\|Y_{0}\|^{2}])\). 1, 250271 (2003). Math. [6, Chap. Since \((Y^{i},W^{i})\), \(i=1,2\), are two solutions with \(Y^{1}_{0}=Y^{2}_{0}=y\), Cherny [8, Theorem3.1] shows that \((W^{1},Y^{1})\) and \((W^{2},Y^{2})\) have the same law. Ann. Taking \(p(x)=x_{i}\), \(i=1,\ldots,d\), we obtain \(a(x)\nabla p(x) = a(x) e_{i} = 0\) on \(\{x_{i}=0\}\). Google Scholar, Bochnak, J., Coste, M., Roy, M.-F.: Real Algebraic Geometry. The use of polynomial diffusions in financial modeling goes back at least to the early 2000s. Finance. Noting that \(Z_{T}\) is positive, we obtain \({\mathbb {E}}[ \mathrm{e}^{\varepsilon' Z_{T}^{2}}]<\infty\). Then, for all \(t<\tau\). Understanding how polynomials used in real and the workplace influence jobs may help you choose a career path. Finance 17, 285306 (2007), Larsson, M., Ruf, J.: Convergence of local supermartingales and NovikovKazamaki type conditions for processes with jumps (2014). $$, \(\widehat{\mathcal {G}}p= {\mathcal {G}}p\), \(E_{0}\subseteq E\cup\bigcup_{p\in{\mathcal {P}}} U_{p}\), $$ \widehat{\mathcal {G}}p > 0\qquad \mbox{on } E_{0}\cap\{p=0\}. The right-hand side is a nonnegative supermartingale on \([0,\tau)\), and we deduce \(\sup_{t<\tau}Z_{t}<\infty\) on \(\{\tau <\infty \}\), as required. Then for any Also, the business owner needs to calculate the lowest price at which an item can be sold to still cover the expenses. Zhou [ 49] used one-dimensional polynomial (jump-)diffusions to build short rate models that were estimated to data using a generalized method-of-moments approach, relying crucially on the ability to compute moments efficiently. Inserting this into(F.1) yields, for \(t<\tau=\inf\{t: p(X_{t})=0\}\). To see this, suppose for contradiction that \(\alpha_{ik}<0\) for some \((i,k)\). Leveraging decentralised finance derivatives to their fullest potential. These quantities depend on\(x\) in a possibly discontinuous way. For this, in turn, it is enough to prove that \((\nabla p^{\top}\widehat{a} \nabla p)/p\) is locally bounded on \(M\). Hence \(\beta_{j}> (B^{-}_{jI}){\mathbf{1}}\) for all \(j\in J\). Example: xy4 5x2z has two terms, and three variables (x, y and z) These somewhat non digestible predictions came because we tried to fit the stock market in a first degree polynomial equation i.e. on 9, 191209 (2002), Dummit, D.S., Foote, R.M. for all Similarly, with \(p=1-x_{i}\), \(i\in I\), it follows that \(a(x)e_{i}\) is a polynomial multiple of \(1-x_{i}\) for \(i\in I\). Moreover, fixing \(j\in J\), setting \(x_{j}=0\) and letting \(x_{i}\to\infty\) for \(i\ne j\) forces \(B_{ji}>0\). Free shipping & returns in North America. Simple example, the air conditioner in your house. $$, $$ {\mathbb {P}}_{z}[\tau_{0}>\varepsilon] = \int_{\varepsilon}^{\infty}\frac {1}{t\varGamma (\widehat{\nu})}\left(\frac{z}{2t}\right)^{\widehat{\nu}} \mathrm{e}^{-z/(2t)}{\,\mathrm{d}} t, $$, \({\mathbb {P}}_{z}[\tau _{0}>\varepsilon]=\frac{1}{\varGamma(\widehat{\nu})}\int _{0}^{z/(2\varepsilon )}s^{\widehat{\nu}-1}\mathrm{e}^{-s}{\,\mathrm{d}} s\), $$ 0 \le2 {\mathcal {G}}p({\overline{x}}) < h({\overline{x}})^{\top}\nabla p({\overline{x}}). 243, 163169 (1979), Article Then \(0\le{\mathbb {E}}[Z_{\tau}] = {\mathbb {E}}[\int_{0}^{\tau}\mu_{s}{\,\mathrm{d}} s]<0\), a contradiction, whence \(\mu_{0}\ge0\) as desired. and Hence the following local existence result can be proved. Springer, Berlin (1997), Penrose, R.: A generalized inverse for matrices. To this end, consider the linear map \(T: {\mathcal {X}}\to{\mathcal {Y}}\) where, and \(TK\in{\mathcal {Y}}\) is given by \((TK)(x) = K(x)Qx\). This directly yields \(\pi_{(j)}\in{\mathbb {R}}^{n}_{+}\). Finally, let \(\{\rho_{n}:n\in{\mathbb {N}}\}\) be a countable collection of such stopping times that are dense in \(\{t:Z_{t}=0\}\). This proves(i). The proof of(ii) is complete. \(W\). Replacing \(x\) by \(sx\), dividing by \(s\) and sending \(s\) to zero gives \(x_{i}\phi_{i} = \lim_{s\to0} s^{-1}\eta_{i} + ({\mathrm {H}}x)_{i}\), which forces \(\eta _{i}=0\), \({\mathrm {H}}_{ij}=0\) for \(j\ne i\) and \({\mathrm {H}}_{ii}=\phi _{i}\). Am. Available online at http://e-collection.library.ethz.ch/eserv/eth:4629/eth-4629-02.pdf, Cuchiero, C., Keller-Ressel, M., Teichmann, J.: Polynomial processes and their applications to mathematical finance. Let \(C_{0}(E_{0})\) denote the space of continuous functions on \(E_{0}\) vanishing at infinity. Next, since \(a \nabla p=0\) on \(\{p=0\}\), there exists a vector \(h\) of polynomials such that \(a \nabla p/2=h p\). Thus \(a(x)Qx=(1-x^{\top}Qx)\alpha Qx\) for all \(x\in E\). International delivery, from runway to doorway. Finance. \(Z\ge0\), then on of \(E_{0}\). $$, \(\tau_{E}=\inf\{t\colon X_{t}\notin E\}\le\tau\), \(\int_{0}^{t}{\boldsymbol{1}_{\{p(X_{s})=0\} }}{\,\mathrm{d}} s=0\), $$ \begin{aligned} \log& p(X_{t}) - \log p(X_{0}) \\ &= \int_{0}^{t} \left(\frac{{\mathcal {G}}p(X_{s})}{p(X_{s})} - \frac {1}{2}\frac {\nabla p^{\top}a \nabla p(X_{s})}{p(X_{s})^{2}}\right) {\,\mathrm{d}} s + \int_{0}^{t} \frac {\nabla p^{\top}\sigma(X_{s})}{p(X_{s})}{\,\mathrm{d}} W_{s} \\ &= \int_{0}^{t} \frac{2 {\mathcal {G}}p(X_{s}) - h^{\top}\nabla p(X_{s})}{2p(X_{s})} {\,\mathrm{d}} s + \int_{0}^{t} \frac{\nabla p^{\top}\sigma(X_{s})}{p(X_{s})}{\,\mathrm{d}} W_{s} \end{aligned} $$, $$ V_{t} = \int_{0}^{t} {\boldsymbol{1}_{\{X_{s}\notin U\}}} \frac{1}{p(X_{s})}|2 {\mathcal {G}}p(X_{s}) - h^{\top}\nabla p(X_{s})| {\,\mathrm{d}} s. $$, \(E {\cap} U^{c} {\cap} \{x:\|x\| {\le} n\}\), $$ \varepsilon_{n}=\min\{p(x):x\in E\cap U^{c}, \|x\|\le n\} $$, $$ V_{t\wedge\sigma_{n}} \le\frac{t}{2\varepsilon_{n}} \max_{\|x\|\le n} |2 {\mathcal {G}}p(x) - h^{\top}\nabla p(x)| < \infty. \(\mu\) $$, \({\mathcal {V}}( {\mathcal {R}})={\mathcal {V}}(I)\), \(S\subseteq{\mathcal {I}}({\mathcal {V}}(S))\), $$ I = {\mathcal {I}}\big({\mathcal {V}}(I)\big). Like actuaries, statisticians are also concerned with the data collection and analysis. The above proof shows that \(p(X)\) cannot return to zero once it becomes positive. Ann. Taylor Polynomials.

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