The Physics Society of Iran Iranian Journal of Physics Research 1682-6957 26 1 2026 05 22 Effect of external field on the spatial correlations of two trapped micro-spheres in the presence of a wall Effect of external field on the spatial correlations of two trapped micro-spheres in the presence of a wall 91 116 3728 10.47176/ijpr.26.1.02210 FA Setareh Dabbaghchian Department of Physics, University of Guilan, P.O. Box 41335-1914, Rasht, Iran Golnaz Najafi Golvandani Department of Physics, University of Guilan, P.O. Box 41335-1914, Rasht, Iran Seyyed Nader Rasuli School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran and Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom 0000-0002-8238-2182 Journal Article 2025 10 16 <span>One simple combination of particles which captures effect of hydrodynamic interactions consists of two trapped </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>beads, immersed in fluid, each with a single degree of freedom, and fluctuating around its equilibrium </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>positions. Given such a system in the presence of a flat boundary, we consider effect of an external velocity or </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>temperature field on it. The external field drives the two beads system, out of equilibrium. We calculate beads’ </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>auto/cross correlations in the presence of external field, then investigate if these auto/cross correlations can be </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>used to reveal the presence of a possible external field, and its nature. We find that the former question could be </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>answered successfully, while the latter requires additional information or additional degrees of freedom accessible to the observer</span>. <span>One simple combination of particles which captures effect of hydrodynamic interactions consists of two trapped </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>beads, immersed in fluid, each with a single degree of freedom, and fluctuating around its equilibrium </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>positions. Given such a system in the presence of a flat boundary, we consider effect of an external velocity or </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>temperature field on it. The external field drives the two beads system, out of equilibrium. We calculate beads’ </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>auto/cross correlations in the presence of external field, then investigate if these auto/cross correlations can be </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>used to reveal the presence of a possible external field, and its nature. We find that the former question could be </span><strong style="mso-ansi-font-weight: normal;"><span lang="FA">‎</span></strong><span>answered successfully, while the latter requires additional information or additional degrees of freedom accessible to the observer</span>. https://ijpr.iut.ac.ir/article_3728_460b491b917d4185ed1f5be97229721a.pdf