Closed path integrals and the quantum action

Line integrals in space provide a mathematical method for accumulating quantities along a three-dimensional path, such as a thin coiled spring represented by the trajectory curve. The path is defined by a position vector r, which represents the x, y, and z coordinates in terms of a single parameter t, usually time or an angle. As this parameter changes, the vector traces a smooth and continuous curve through space, defining the trajectory.Line Integrals: Scalar-Valued FunctionsFor scalar-valued...

Multiple integrals are often used to evaluate areas, volumes, mass distributions, and other physical quantities over regions in two or three dimensions. In many problems, however, the original region may have complicated curved boundaries when expressed in Cartesian coordinates. These complex boundaries can make the limits of integration difficult to describe and the overall calculation cumbersome. To simplify the evaluation process, a change of variables is introduced that transforms the...

A line integral for a vector field is defined as the integral of the dot product of a vector function with an infinitesimal displacement vector along a prescribed path. If the prescribed path is closed, the integrals reduce to a closed-line integral. The closed-contour integral of the vector field is referred to in terms of the circulation of the vector field around the closed path. A vector with zero circulation around every closed path is called a conservative field, while one with non-zero...

Vector-valued functions provide a convenient framework for describing motion in space when both magnitude and direction are important. A drone’s velocity at any instant has a direction and a speed, and as the drone moves, both can change. A vector-valued function captures this behavior by assigning to each time a vector whose components are real-valued functions. Each component represents motion along a particular axis in space. Such functions can describe motion in either two-dimensional or...

Evaluating Areas Under Curves with DiscontinuitiesA definite integral is considered improper when the integrand is discontinuous at one of the limits of integration. This occurs when the function is undefined or becomes infinite at an endpoint, making the corresponding region under the curve unbounded. Such behavior is commonly associated with vertical asymptotes at the boundary of the interval. To properly define and evaluate these integrals, a limiting process is used to determine whether a...

Line integrals in the plane provide a method for evaluating quantities distributed along a curve, such as mass, work, or surface area. A curve C in the plane is commonly represented parametrically by x = x(t) and y = y(t), where the parameter t varies over an interval [a, b]. This representation allows geometric and physical quantities to be expressed in terms of a single variable, facilitating both analysis and computation.A line integral of a scalar function f(x, y) along a curve C is defined...