<p>In this paper, we present a regularity criterion to the Navier–Stokes equations based on one entry of the velocity gradient. In fact, we prove that the weak solution to the Navier-Stokes equations is regular provided that <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\partial _{3}u_{3}\in L^{\beta }(0, T; L^{\alpha }(\mathbb {R} ^{3}))\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>∂</mi> <mn>3</mn> </msub> <msub> <mi>u</mi> <mn>3</mn> </msub> <mo>∈</mo> <msup> <mi>L</mi> <mi>β</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mn>0</mn> <mo>,</mo> <mi>T</mi> <mo>;</mo> <msup> <mi>L</mi> <mi>α</mi> </msup> <mrow> <mo stretchy="false">(</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mn>3</mn> </msup> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> with <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\alpha &gt;\frac{7+\sqrt{13}}{6}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>α</mi> <mo>&gt;</mo> <mfrac> <mrow> <mn>7</mn> <mo>+</mo> <msqrt> <mn>13</mn> </msqrt> </mrow> <mn>6</mn> </mfrac> </mrow> </math></EquationSource> </InlineEquation> and: <Equation ID="Equ29"> <EquationSource Format="TEX">\(\begin{aligned} \frac{2}{\beta }+\frac{3}{\alpha }= \frac{-12\,\widehat{\alpha }^{2}+28\, \widehat{\alpha }-3+\sqrt{ (3-2\, \widehat{\alpha })(-72\,\widehat{\alpha }^{3}+276\, \widehat{\alpha }^{2}-374\,\widehat{\alpha }+195)}}{8(2-\widehat{\alpha })}, \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <mfrac> <mn>2</mn> <mi>β</mi> </mfrac> <mo>+</mo> <mfrac> <mn>3</mn> <mi>α</mi> </mfrac> <mo>=</mo> <mfrac> <mrow> <mo>-</mo> <mn>12</mn> <mspace width="0.166667em" /> <msup> <mover accent="true"> <mi>α</mi> <mo stretchy="true">^</mo> </mover> <mn>2</mn> </msup> <mo>+</mo> <mn>28</mn> <mspace width="0.166667em" /> <mover accent="true"> <mi>α</mi> <mo stretchy="true">^</mo> </mover> <mo>-</mo> <mn>3</mn> <mo>+</mo> <msqrt> <mrow> <mrow> <mo stretchy="false">(</mo> <mn>3</mn> <mo>-</mo> <mn>2</mn> <mspace width="0.166667em" /> <mover accent="true"> <mi>α</mi> <mo stretchy="true">^</mo> </mover> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <mo>-</mo> <mn>72</mn> <mspace width="0.166667em" /> <msup> <mover accent="true"> <mi>α</mi> <mo stretchy="true">^</mo> </mover> <mn>3</mn> </msup> <mo>+</mo> <mn>276</mn> <mspace width="0.166667em" /> <msup> <mover accent="true"> <mi>α</mi> <mo stretchy="true">^</mo> </mover> <mn>2</mn> </msup> <mo>-</mo> <mn>374</mn> <mspace width="0.166667em" /> <mover accent="true"> <mi>α</mi> <mo stretchy="true">^</mo> </mover> <mo>+</mo> <mn>195</mn> <mo stretchy="false">)</mo> </mrow> </mrow> </msqrt> </mrow> <mrow> <mn>8</mn> <mo stretchy="false">(</mo> <mn>2</mn> <mo>-</mo> <mover accent="true"> <mi>α</mi> <mo stretchy="true">^</mo> </mover> <mo stretchy="false">)</mo> </mrow> </mfrac> <mo>,</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>where <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\( \widehat{\alpha }=\frac{1}{\alpha }.\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mover accent="true"> <mi>α</mi> <mo stretchy="true">^</mo> </mover> <mo>=</mo> <mfrac> <mn>1</mn> <mi>α</mi> </mfrac> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation> This result improves the previous result obtained by Zujin Zhang and Yali Zhang in (Z. Angew. Math. Phys.)(2021), which states the similar result for <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\alpha \ge \frac{3+\sqrt{17}}{4}.\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>α</mi> <mo>≥</mo> <mfrac> <mrow> <mn>3</mn> <mo>+</mo> <msqrt> <mn>17</mn> </msqrt> </mrow> <mn>4</mn> </mfrac> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation> Notice that <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\frac{7+\sqrt{13}}{6}&lt;\frac{3+\sqrt{17}}{4},\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mfrac> <mrow> <mn>7</mn> <mo>+</mo> <msqrt> <mn>13</mn> </msqrt> </mrow> <mn>6</mn> </mfrac> <mo>&lt;</mo> <mfrac> <mrow> <mn>3</mn> <mo>+</mo> <msqrt> <mn>17</mn> </msqrt> </mrow> <mn>4</mn> </mfrac> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> thus the range of <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>α</mi> </math></EquationSource> </InlineEquation> is changed. Also, we show that <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\beta \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>β</mi> </math></EquationSource> </InlineEquation> corresponding to <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>α</mi> </math></EquationSource> </InlineEquation> which is obtained in our result is smaller than <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\beta \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>β</mi> </math></EquationSource> </InlineEquation> obtained in the mentioned paper.</p>

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The Regularity Criterion to the Navier–Stokes Equations Based on One Entry of the Velocity Gradient

  • Khadijeh Baghaei

摘要

In this paper, we present a regularity criterion to the Navier–Stokes equations based on one entry of the velocity gradient. In fact, we prove that the weak solution to the Navier-Stokes equations is regular provided that \(\partial _{3}u_{3}\in L^{\beta }(0, T; L^{\alpha }(\mathbb {R} ^{3}))\) 3 u 3 L β ( 0 , T ; L α ( R 3 ) ) with \(\alpha >\frac{7+\sqrt{13}}{6}\) α > 7 + 13 6 and: \(\begin{aligned} \frac{2}{\beta }+\frac{3}{\alpha }= \frac{-12\,\widehat{\alpha }^{2}+28\, \widehat{\alpha }-3+\sqrt{ (3-2\, \widehat{\alpha })(-72\,\widehat{\alpha }^{3}+276\, \widehat{\alpha }^{2}-374\,\widehat{\alpha }+195)}}{8(2-\widehat{\alpha })}, \end{aligned}\) 2 β + 3 α = - 12 α ^ 2 + 28 α ^ - 3 + ( 3 - 2 α ^ ) ( - 72 α ^ 3 + 276 α ^ 2 - 374 α ^ + 195 ) 8 ( 2 - α ^ ) , where \( \widehat{\alpha }=\frac{1}{\alpha }.\) α ^ = 1 α . This result improves the previous result obtained by Zujin Zhang and Yali Zhang in (Z. Angew. Math. Phys.)(2021), which states the similar result for \(\alpha \ge \frac{3+\sqrt{17}}{4}.\) α 3 + 17 4 . Notice that \(\frac{7+\sqrt{13}}{6}<\frac{3+\sqrt{17}}{4},\) 7 + 13 6 < 3 + 17 4 , thus the range of \(\alpha \) α is changed. Also, we show that \(\beta \) β corresponding to \(\alpha \) α which is obtained in our result is smaller than \(\beta \) β obtained in the mentioned paper.