Suppose $S$ is a positive definite, real and symmetric $n\times n$ matrix and let $x\in\mathbb{R}^n$. Consider the quantity
$$ \langle(Sx)_i,(Sx)_j\rangle $$ Is it true that this quantity is positive for every $x\neq0$? How to prove it?
Thank you.
2026-05-06 08:27:18.1778056038
Scalar Product with positive definite matrix
60 Views Asked by Bumbble Comm https://math.techqa.club/user/bumbble-comm/detail AtRelated Questions in LINEAR-ALGEBRA
- An underdetermined system derived for rotated coordinate system
- How to prove the following equality with matrix norm?
- Alternate basis for a subspace of $\mathcal P_3(\mathbb R)$?
- Why the derivative of $T(\gamma(s))$ is $T$ if this composition is not a linear transformation?
- Why is necessary ask $F$ to be infinite in order to obtain: $ f(v)=0$ for all $ f\in V^* \implies v=0 $
- I don't understand this $\left(\left[T\right]^B_C\right)^{-1}=\left[T^{-1}\right]^C_B$
- Summation in subsets
- $C=AB-BA$. If $CA=AC$, then $C$ is not invertible.
- Basis of span in $R^4$
- Prove if A is regular skew symmetric, I+A is regular (with obstacles)
Related Questions in INNER-PRODUCTS
- Inner Product Same for all Inputs
- How does one define an inner product on the space $V=\mathbb{Q}_p^n$?
- Inner Product Uniqueness
- Is the natural norm on the exterior algebra submultiplicative?
- Norm_1 and dot product
- Is Hilbert space a Normed Space or a Inner Product Space? Or it have to be both at the same time?
- Orthonormal set and linear independence
- Inner product space and orthogonal complement
- Which Matrix is an Inner Product
- Proof Verification: $\left\|v-\frac{v}{\|v\|}\right\|= \min\{\|v-u\|:u\in S\}$
Related Questions in POSITIVE-DEFINITE
- Show that this matrix is positive definite
- A minimal eigenvalue inequality for Positive Definite Matrix
- Show that this function is concave?
- $A^2$ is a positive definite matrix.
- Condition for symmetric part of $A$ for $\|x(t)\|$ monotonically decreasing ($\dot{x} = Ax(t)$)
- The determinant of the sum of a positive definite matrix with a symmetric singular matrix
- Using complete the square to determine positive definite matrices
- How the principal submatrix of a PSD matrix could be positive definite?
- Aribtrary large ratio for eigenvalues of positive definite matrices
- Positive-definiteness of the Schur Complement
Related Questions in SYMMETRIC-MATRICES
- $A^2$ is a positive definite matrix.
- Showing that the Jacobi method doesn't converge with $A=\begin{bmatrix}2 & \pm2\sqrt2 & 0 \\ \pm2\sqrt2&8&\pm2\sqrt2 \\ 0&\pm2\sqrt2&2 \end{bmatrix}$
- Is $A-B$ never normal?
- Is a complex symmetric square matrix with zero diagonal diagonalizable?
- Symmetry of the tetrahedron as a subgroup of the cube
- Rotating a matrix to become symmetric
- Diagonalize real symmetric matrix
- How to solve for $L$ in $X = LL^T$?
- Showing a block matrix is SPD
- Proving symmetric matrix has positive eigenvalues
Trending Questions
- Induction on the number of equations
- How to convince a math teacher of this simple and obvious fact?
- Find $E[XY|Y+Z=1 ]$
- Refuting the Anti-Cantor Cranks
- What are imaginary numbers?
- Determine the adjoint of $\tilde Q(x)$ for $\tilde Q(x)u:=(Qu)(x)$ where $Q:U→L^2(Ω,ℝ^d$ is a Hilbert-Schmidt operator and $U$ is a Hilbert space
- Why does this innovative method of subtraction from a third grader always work?
- How do we know that the number $1$ is not equal to the number $-1$?
- What are the Implications of having VΩ as a model for a theory?
- Defining a Galois Field based on primitive element versus polynomial?
- Can't find the relationship between two columns of numbers. Please Help
- Is computer science a branch of mathematics?
- Is there a bijection of $\mathbb{R}^n$ with itself such that the forward map is connected but the inverse is not?
- Identification of a quadrilateral as a trapezoid, rectangle, or square
- Generator of inertia group in function field extension
Popular # Hahtags
second-order-logic
numerical-methods
puzzle
logic
probability
number-theory
winding-number
real-analysis
integration
calculus
complex-analysis
sequences-and-series
proof-writing
set-theory
functions
homotopy-theory
elementary-number-theory
ordinary-differential-equations
circles
derivatives
game-theory
definite-integrals
elementary-set-theory
limits
multivariable-calculus
geometry
algebraic-number-theory
proof-verification
partial-derivative
algebra-precalculus
Popular Questions
- What is the integral of 1/x?
- How many squares actually ARE in this picture? Is this a trick question with no right answer?
- Is a matrix multiplied with its transpose something special?
- What is the difference between independent and mutually exclusive events?
- Visually stunning math concepts which are easy to explain
- taylor series of $\ln(1+x)$?
- How to tell if a set of vectors spans a space?
- Calculus question taking derivative to find horizontal tangent line
- How to determine if a function is one-to-one?
- Determine if vectors are linearly independent
- What does it mean to have a determinant equal to zero?
- Is this Batman equation for real?
- How to find perpendicular vector to another vector?
- How to find mean and median from histogram
- How many sides does a circle have?