Information: - Mathematics (from Greek "mathma", knowledge, study, learning) is the study of topics such as quantity (numbers), structure, space, and change. There is a range of views among mathematicians and philosophers as to the exact scope and definition of mathematics. - The Fourier transform decomposes a function of time (a "signal") into the frequencies that make it up, in a way similar to how a musical chord can be expressed as the frequencies (or pitches) of its constituent notes. The Fourier transform of a function of time itself is a complex-valued function of frequency, whose absolute value represents the amount of that frequency present in the original function, and whose complex argument is the phase offset of the basic sinusoid in that frequency. The Fourier transform is called the "frequency domain representation" of the original signal. The term "Fourier transform" refers to both the frequency domain representation and the mathematical operation that associates the frequency domain representation to a function of time. The Fourier transform is not limited to functions of time, but in order to have a unified language, the domain of the original function is commonly referred to as the "time domain". For many functions of practical interest, one can define an operation that reverses this: the "inverse Fourier transformation", also called "Fourier synthesis", of a frequency domain representation combines the contributions of all the different frequencies to recover the original function of time. - Alexandru Ghika ( June 22 , 1902 -- April 11 , 1964 ) was a Romanian mathematician , founder of the Romanian school of functional analysis . - A mathematician is someone who uses an extensive knowledge of mathematics in his/her work, typically to solve mathematical problems. - Mathematical analysis is the branch of mathematics dealing with limits and related theories, such as differentiation, integration, measure, infinite series, and analytic functions. - Functional analysis is a branch of mathematical analysis, the core of which is formed by the study of vector spaces endowed with some kind of limit-related structure (e.g. inner product, norm, topology, etc.) and the linear functions defined on these spaces and respecting these structures in a suitable sense. The historical roots of functional analysis lie in the study of spaces of functions and the formulation of properties of transformations of functions such as the Fourier transform as transformations defining continuous, unitary etc. operators between function spaces. This point of view turned out to be particularly useful for the study of differential and integral equations. - A mathematical problem is a problem that is amenable to being represented, analyzed, and possibly solved, with the methods of mathematics. This can be a real-world problem, such as computing the orbits of the planets in the solar system, or a problem of a more abstract nature, such as Hilbert's problems.<br> It can also be a problem referring to the nature of mathematics itself, such as Russell's Paradox. Given the information above, choose from the list below the object entity that exhibits the relation 'field of work' with the subject 'alexandru ghika'. Choices: - computing - functional analysis - mathematical analysis - mathematician - mathematics - musical
mathematical analysis

Information: - The was a series of battles undertaken by the Tokugawa shogunate against the Toyotomi clan, and ending in that clan's destruction. Divided into two stages (Winter Campaign and Summer Campaign), and lasting from 1614 to 1615, the siege put an end to the last major armed opposition to the shogunate's establishment. The end of the conflict is sometimes called the , because the era name was changed from Keich to Genna immediately following the siege. - A or was a covert agent or mercenary in feudal Japan. The functions of the ninja included espionage, sabotage, infiltration, assassination and guerrilla warfare. Their covert methods of waging irregular warfare were deemed "dishonorable" and "beneath" the samurai-caste, who observed strict rules about honor and combat. The "shinobi" proper, a specially trained group of spies and mercenaries, appeared in the 15th century during the Sengoku period, but antecedents may have existed in the 14th century, and possibly in the 12th century (Heian or early Kamakura era). - Hattori Masanari ( , 1565 -- June 3 , 1615 ) was the third Hattori Hanz and a retainer under the Tokugawa clan during the late Sengoku period of Japanese history . He was the eldest son of the famous Hattori Hanz . Masanari began to fight alongside his father by the mid 1590s , succeeding him in 1596 at age 31 . Following the Battle of Sekigahara of 1600 , Masanari was enlisted by Tokugawa Ieyasu as captain of the Edo Castle guards . The band of Iga placed under his command , however , rebelled in response to Masanari 's treatment causing him to be utterly humiliated in the face of the Tokugawa . While tracking two members who had fled , he killed a man in what turned out to be a case of mistaken identity and was relieved of his position . In order to repair the Hattori name and his reputation , Masanari valiantly fought during the Siege of Osaka in 1614 - 1615 as head of 60 Iga ninja . He was cut down in the process of the second siege of Osaka , and was succeeded by his brother Hattori Masashige . - He fought his first battle at 20 years old (Battle of Sekigahara) and went on to fight in the Siege of Osaka after his brothers death at Osaka he succeeded him and became leader of the Iga ninja. He went on to serve the Tokugawa after they secured the shogunate. Given the information above, choose from the list below the object entity that exhibits the relation 'occupation' with the subject 'hattori masanari'. Choices: - agent - covert agent - leader - major - mercenary - ninja - samurai
samurai