• Title/Summary/Keyword: 2-normed spaces

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ERROR ESTIMATES FOR A SINGLE-PHASE NONLINEAR STEFAN PROBLEM IN ONE SPACE DIMENSION

  • Lee, H.Y.;Ohm, M.R.;Shin, J.Y.
    • Journal of the Korean Mathematical Society
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    • v.34 no.3
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    • pp.661-672
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    • 1997
  • In this paper we introduce the semidiscrete solution of a single-phase nonlinear Stefan problem We analyze the optimal convergence of the semidiscrete solution in $H^1$ and $H^2$ normed spaces and also we derive the error estimates in $L^2$ normed space.

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ORTHOGONAL STABILITY OF AN EULER-LAGRANGE-JENSEN (a, b)-CUBIC FUNCTIONAL EQUATION

  • Pasupathi, Narasimman;Rassias, John Michael;Lee, Jung Rye;Shim, Eun Hwa
    • The Pure and Applied Mathematics
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    • v.29 no.2
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    • pp.189-199
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    • 2022
  • In this paper, we introduce a new generalized (a, b)-cubic Euler-Lagrange-Jensen functional equation and obtain its general solution. Furthermore, we prove the Hyers-Ulam stability of the new generalized (a, b)-cubic Euler-Lagrange-Jensen functional equation in orthogonality normed spaces.

APPROXIMATE ADDITIVE MAPPINGS IN 2-BANACH SPACES AND RELATED TOPICS: REVISITED

  • YUN, SUNGSIK
    • Korean Journal of Mathematics
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    • v.23 no.3
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    • pp.393-399
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    • 2015
  • W. Park [J. Math. Anal. Appl. 376 (2011) 193-202] proved the Hyers-Ulam stability of the Cauchy functional equation, the Jensen functional equation and the quadratic functional equation in 2-Banach spaces. But there are serious problems in the control functions given in all theorems of the paper. In this paper, we correct the statements of these results and prove the corrected theorems. Moreover, we prove the superstability of the Cauchy functional equation, the Jensen functional equation and the quadratic functional equation in 2-Banach spaces under the original given conditions.

A FIXED POINT APPROACH TO THE STABILITY OF QUINTIC MAPPINGS IN QUASI β-NORMED SPACES

  • Koh, Heejeong
    • Journal of the Chungcheong Mathematical Society
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    • v.26 no.4
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    • pp.757-767
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    • 2013
  • We investigate the general solution of the following functional equation and the generalized Hyers-Ulam-Rassias stability problem in quasi ${\beta}$-normed spaces and then the stability by using alternative fixed point method for the following quintic function $f:X{\rightarrow}Y$ such that f(3x+y)+f(3x-y)+5[f(x+y)+f(x-y)]=4[f(2x+y)+f(2x-y)]+2f(3x)-246f(x), for all $x,y{\in}X$.

STABILITY OF QUADRATIC FUNCTIONAL EQUATIONS IN RANDOM NORMED SPACES

  • Schin, Seung Won;Ki, DoHyeong;Chang, JaeWon;Kim, Min June;Park, Choonkil
    • Korean Journal of Mathematics
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    • v.18 no.4
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    • pp.395-407
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    • 2010
  • In this paper, we prove the generalized Hyers-Ulam stability of the following quadratic functional equations $$cf\(\sum_{i=1}^{n}x_i\)+\sum_{j=2}^{n}f\(\sum_{i=1}^{n}x_i-(n+c-1)x_j\)\\=(n+c-1)\(f(x_1)+c\sum_{i=2}^{n}f(x_i)+\sum_{i<j,j=3}^{n}\(\sum_{i=2}^{n-1}f(x_i-x_j\)\),\\Q\(\sum_{i=1}^{n}d_ix_i\)+\sum_{1{\leq}i<j{\leq}n}d_id_jQ(x_i-x_j)=\(\sum_{i=1}^{n}d_i\)\(\sum_{i=1}^{n}d_iQ(x_i)\)$$ in random normed spaces.

A CHARACTERIZATION OF REFLEXIVITY OF NORMED ALMOST LINEAR SPACES

  • Im, Sung-Mo;Lee, Sang-Han
    • Communications of the Korean Mathematical Society
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    • v.12 no.2
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    • pp.211-219
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    • 1997
  • In [6] we proved that if a nals X is reflexive, then $X = W_X + V_X$ . In this paper we show that, for a split nals $X = W_X + V_X$, X is reflecxive if and only if $V_X$ and $W_X$ are reflcxive.

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ON MATRIX NORMED SPACES

  • Shin, Dong-Yun;Lee, Sa-Ge;Byun, Chang-Ho;Kim, Sang-Og
    • Bulletin of the Korean Mathematical Society
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    • v.27 no.2
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    • pp.103-112
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    • 1990
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APPROXIMATE ADDITIVE-QUADRATIC MAPPINGS AND BI-JENSEN MAPPINGS IN 2-BANACH SPACES

  • Park, Won-Gil
    • Journal of the Chungcheong Mathematical Society
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    • v.30 no.4
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    • pp.467-476
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    • 2017
  • In this paper, we obtain the stability of the additive-quadratic functional equation f(x+y, z+w)+f(x+y, z-w) = 2f(x, z)+2f(x, w)+2f(y, z)+2f(y, w) and the bi-Jensen functional equation $$4f(\frac{x+y}{2},\;\frac{z+w}{2})=f(x,\;z)+f(x,\;w)+f(y,\;z)+f(y,\;w)$$ in 2-Banach spaces.

ON AN ADDITIVE FUNCTIONAL INEQUALITY IN NORMED MODULES OVER A $C^*$-ALGEBRA

  • An, Jong-Su
    • The Pure and Applied Mathematics
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    • v.15 no.4
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    • pp.393-400
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    • 2008
  • In this paper, we investigate the following additive functional inequality (0.1) ||f(x)+f(y)+f(z)+f(w)||${\leq}$||f(x+y)+f(z+w)|| in normed modules over a $C^*$-algebra. This is applied to understand homomor-phisms in $C^*$-algebra. Moreover, we prove the generalized Hyers-Ulam stability of the functional inequality (0.2) ||f(x)+f(y)+f(z)f(w)||${\leq}$||f(x+y+z+w)||+${\theta}||x||^p||y||^p||z||^p||w||^p$ in real Banach spaces, where ${\theta}$, p are positive real numbers with $4p{\neq}1$.

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