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Featured researches published by Un Cig Ji.


Nagoya Mathematical Journal | 1997

Transforms on white noise functionals with their applications to Cauchy problems

Dong Myung Chung; Un Cig Ji

A generalized Laplacian Δ G (K) is defined as a continuous linear operator acting on the space of test white noise functionals. Operator-parameter - and -transforms on white noise functionals are introduced and then prove a characterization theorem for and -transforms in terms of the coordinate differential operator and the coordinate multiplication. As an application, we investigate the existence and uniqueness of solution of the Cauchy problem for the heat equation associated with Δ G (K)


Infinite Dimensional Analysis, Quantum Probability and Related Topics | 2002

ANALYTIC CHARACTERIZATION OF GENERALIZED FOCK SPACE OPERATORS AS TWO-VARIABLE ENTIRE FUNCTIONS WITH GROWTH CONDITION

Un Cig Ji; Nobuaki Obata; Habib Ouerdiane

Duality is established for new spaces of entire functions in two infinite dimensional variables with certain growth rates determined by Young functions. These entire functions characterize the symbols of generalized Fock space operators. As an application, a proper space is found for a solution to a normal-ordered white noise differential equation having highly singular coefficients.


Reviews in Mathematical Physics | 2002

QUANTUM STOCHASTIC ANALYSIS VIA WHITE NOISE OPERATORS IN WEIGHTED FOCK SPACE

Dong Myung Chung; Un Cig Ji; Nobuaki Obata

White noise theory allows to formulate quantum white noises explicitly as elemental quantum stochastic processes. A traditional quantum stochastic differential equation of Ito type is brought into a normal-ordered white noise differential equation driven by lower powers of quantum white noises. The class of normal-ordered white noise differential equations covers quantum stochastic differential equations with highly singular noises such as higher powers or higher order derivatives of quantum white noises, which are far beyond the traditional Ito theory. For a general normal-ordered white noise differential equation unique existence of a solution is proved in the sense of white noise distribution. Its regularity properties are investigated by means of weighted Fock spaces interpolating spaces of white noise distributions and associated characterization theorems for S-transform and for operator symbols.


Infinite Dimensional Analysis, Quantum Probability and Related Topics | 2009

Exotic laplacians and associated stochastic processes

Luigi Accardi; Un Cig Ji; Kimiaki Saitô

In this paper, we give a decomposition of the space of tempered distributions by the Cesaro norm, and for any we construct directly from the exotic trace an infinite dimensional separable Hilbert space Hc,2a-1 on which the exotic trace plays the role as the usual trace. This implies that the Exotic Laplacian coincides with the Volterra–Gross Laplacian in the Boson Fock space Γ(Hc,2a-1) over the Hilbert space Hc,2a-1. Finally we construct the Brownian motion naturally associated to the Exotic Laplacian of order 2a-1 and we find an explicit expression for the associated heat semigroup.


Infinite Dimensional Analysis, Quantum Probability and Related Topics | 1999

CAUCHY PROBLEMS ASSOCIATED WITH THE LÉVY LAPLACIAN IN WHITE NOISE ANALYSIS

Dong Myung Chung; Un Cig Ji; Kimiaki Saitô

In this paper we shall discuss the existence and the uniqueness of solutions of the heat type equation and the wave type equation associated with the Levy Laplacian acting on a domain in the space of generalized white noise functionals.


Infinite Dimensional Analysis, Quantum Probability and Related Topics | 1998

Higher Powers of Quantum White Noises in Terms of Integral Kernel Operators

Dong Myung Chung; Un Cig Ji; Nobuaki Obata

A rigorous mathematical formulation of higher powers of quantum white noises is given on the basis of the most recent theory of white noise distributions due to Cochran, Kuo and Sengupta. The renormalized quantum Ito formula due to Accardi, Lu and Volovich is derived from the renormalized product formula based on integral kernel operators on white noise functions. During the discussion, the analytic characterization of operator symbols and the expansion theorem for a white noise operator in terms of integral kernel operators are established.


Journal of Functional Analysis | 2003

Stochastic integral representation theorem for quantum semimartingales

Un Cig Ji

Abstract The quantum stochastic integral of Ito type formulated by Hudson and Parthasarathy is extended to a wider class of adapted quantum stochastic processes on Boson Fock space. An Ito formula is established and a quantum stochastic integral representation theorem is proved for a class of unbounded semimartingales which includes polynomials and (Wick) exponentials of the basic martingales in quantum stochastic calculus.


Infinite Dimensional Analysis, Quantum Probability and Related Topics | 2011

EXOTIC LAPLACIANS AND DERIVATIVES OF WHITE NOISE

Luigi Accardi; Un Cig Ji; Kimiaki Saitô

In this paper, we give a relationship between the exotic Laplacians and the Levy Laplacians in terms of the higher-order derivatives of white noise by introducing a bijective and continuous linear operator acting on white noise functionals. Moreover, we study a relationship between exotic Laplacians, acting on higher-order singular functionals, each other in terms of the constructed operator.


Stochastics An International Journal of Probability and Stochastic Processes | 2009

Quantum stochastic integral representations of Fock space operators

Un Cig Ji; Nobuaki Obata

An (unbounded) operator Ξ on Boson Fock space over L 2(R +) is called regular if it is an admissible white noise operator such that the conditional expectations give rise to a regular quantum martingale. We prove that an admissible white noise operator is regular if and only if it admits a quantum stochastic integral representation.


Journal of Mathematical Physics | 2010

On KSGNS representations on Krein C∗-modules

Jaeseong Heo; Jang Pyo Hong; Un Cig Ji

Motivated by the notion of P-functional, we introduce a notion of α-completely positive map between  ∗-algebras which is a Hermitian map satisfying a certain positivity condition, and then a α-completely positive map which is not completely positive is constructed. We establish the Kasparov-Stinespring-Gelfand-Naimark-Segal constructions of C∗-algebra and  ∗-algebra on Krein C∗-modules with α-completely positive maps.

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Byoung Jin Choi

Chungbuk National University

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Young Yi Kim

Chungbuk National University

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Luigi Accardi

University of Rome Tor Vergata

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V. P. Belavkin

University of Nottingham

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Yongdo Lim

Sungkyunkwan University

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Yoon Jung Park

Chungbuk National University

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