Tagged Questions

For questions about trace, which can concern matrices, operators or functions.

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0answers
15 views

Trace norm identity (in bra-ket notation)

I came across the following identity in a paper: $$ \|\hspace{0.3em}|v\rangle\langle v| - |w\rangle\langle w|\hspace{0.3em}\|_{tr}=2\sqrt{1-|\langle v|w\rangle |^2}$$ where the norm on the left is ...
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1answer
20 views

Lie group as a subset of its Lie algebra

Consider a (possibly infinite-dimensional) Lie group $\mathcal{G}$ and let $\mathcal{A}$ be an algebra with a product $\cdot$ and the bracket $[u,v]=u\cdot v - v\cdot u$. The following statement is ...
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0answers
25 views

Prove that theorems about trace of matrix: [closed]

$ 1-) $    If A is an nxn symmetric matrix with r nonzero characteristic roots $ \lambda_1,\lambda_2,...,\lambda_r $, then $ tr(A^-)=\sum_{i=1}^r \lambda_i^{-1}$ $ 2-) ...
2
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1answer
51 views

A hard exercise on endomorphisms and determinants

The following exercise has been bugging me for some days, could someone help me with it ? Let $E$ be a $\mathbb{C}$-vector space with dimension $n$ and $f\in\mathcal{L}(E)$ ($\mathcal{L}(E)$ denotes ...
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0answers
49 views

Trace of a certain matrix

Let $A$ be a $227 \times 227$ matrix having distinct eigenvalues , with entries from $\mathbb Z_{227}$ , then what is the trace of $A$ ?
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1answer
29 views

$\operatorname{tr}(AB) = 0$ for (skew-)symmetric matricies

I know if A is symmetric and B is skew-symmetric then $\operatorname{tr}(AB) = 0$. (This follows because $\operatorname{tr}(AB) = -\operatorname{tr}(AB) $) Is the converse of that true? In other ...
2
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0answers
22 views

Equivalent definitions of the trace of a Hilbert-Schmidt operator

I am currently reading the book Spectral Methods in Automorphic Forms, and Iwaniec defines the trace operator in a different way than I am accustomed to. Throughout, assume that everything converges ...
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2answers
18 views

Proving a theorem about trace of matrix which involving generalized inverse matrix

can you prove that theorem for me: Let A be mxn matrix of rank r then, $\ tr[I-A(A'A)^-A'] = m-r $  .   $\ A' $(transpose of A) ,$\ A^- $(generalized inverse of A)
2
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2answers
31 views

Proof that theorems about trace of matrix :

Can somebody help me about proofs of this theorems A is an nxn matrix and $\ A^2$ = mA then, tr(A) = m rank(A) . A is an nxn matrix and k is a positive integer then, tr($\ A^k$) = $\sum_{i=1}^n ...
0
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3answers
41 views

Trace of a power of a matrix product

Suppose I have two 2x2 matrices $A$ and $B$. What can I say about $Tr(A^k B^k)$ versus $Tr((AB)^k)$? I know that if there is some cyclic permutation that takes $A\cdot A\cdots A B\cdot B\cdots B$ to ...
0
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1answer
37 views

Partial derivative of the trace of matrix entry-wise exponential?

Just checking my math here and getting some help for the exponential part. $\renewcommand{\v}[1]{\mathrm{vec}\left(#1\right)} \renewcommand{\m}[1]{\mathbf{#1}} ...
0
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1answer
39 views

Finding trace of a matrix $A $ such that $A^3=A$ [closed]

If $A$ is a real $n \times n$ matrix satisfying $A^3 = A,$ then Trace of $A$ is always 1) $n$ 2) 0 3) $−n$ 4) an integer in the set $\{−n,−(n − 1), \dots ,−1, 0, 1, \dots , n\}.$ how to solve ...
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1answer
57 views

Finding the trace of $(I + \Sigma^{-1} AA^T)^{-1}$

I need to efficiently compute the trace of $$ B = (I + \Sigma^{-1} AA^T)^{-1} $$ where $\Sigma$ is diagonal and all its elements strictly greater than zero. $A$ is $-1$ on the diagonal and $1$ right ...
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2answers
38 views

Is this Determinant and Trace identity equivalent to Unitary matrix?

Thanks for any help in advance. I have this equality for a 2x2 invertible complex matrix: $$\text{Tr}(AA^*)=2|\text{det}(A)|^2$$ where $*$ is complex conjugate transposition. Is this equality ...
0
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3answers
75 views

Positive semi-definite matrix has a non-negative trace?

A simple question: If $A$ is a positive semi-definite matrix ($A\succeq 0)$, does it imply $Tr(A)\geq 0$, where the $Tr(\cdot)$ denotes the trace. If not, any counter-example? Thanks.
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1answer
41 views

Equation involving a partial trace

Is there, in general, a solution to the following equation? $\text{Tr}_{V_1}(A(X\otimes I_{V_2})) = B$ where A is an operator on $V_1\otimes V_2$, $B$ is an operator on $V_2$, $I_{V_2}$ is the ...
1
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0answers
16 views

Inclusion of commutators on classical pseudodifferential operators

We denote by $Cl^\mu$ the class of classical pseudo-differential operators of order $\mu$. Consider the notation $$[Cl^{a},Cl^{b}]\hookrightarrow [Cl^{a'},Cl^{b'}]$$ which means that a commutator on ...
0
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1answer
44 views

Proof of Hopf's Lemma

This is a segment of the proof to "Hopf's Lemma," from page 348 of PDE Evans, 2nd edition. I have a question regarding this, at the bottom of this post. Proof. 1. Assume $c \ge 0$. We may as well ...
3
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1answer
45 views

Show that the trace class operators on a Hilbert space form an ideal

Let $(H, (\cdot, \cdot))$ be a separable Hilbert space over $\mathbb{L} = \mathbb{R}$ or $\mathbb{C}$. Suppose that $\{\phi_n\}_{n=1}^\infty$ is an orthonormal basis for $H$. Let $\mathcal{B}(H)$ ...
5
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1answer
118 views

Derivative of determinant of symmetric matrix wrt a scalar

For a given square symmetric invertible matrix $\mathbf{X}$ and scalar $\alpha$ (such that the entries of $\mathbf{X}$ depend on $\alpha$), I would like to use the following well-known expression for ...
0
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0answers
18 views

Traces and linear combinations of idempotents

Let $R$ be a commutative ring and $S$ a subring, and consider the following conditions on an $n$ by $n$ matrix $A$ with entries in $R$: (a) $A$ is an $S$-linear combination of idempotents of ...
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0answers
10 views

Reference request: result concerning Leray trace

Let $V$ be a vector space (possibly of infinite dimension). For a linear homomorphism $f\colon V\to V$ define $$N(f)=\bigcup_{n\in\mathbb{N}} \operatorname{ker}(\underbrace{f\circ\ldots\circ ...
2
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1answer
43 views

Is the trace of an idempotent matrix a sum of idempotents?

Let $R$ be a commutative ring, $n$ a positive integer, and $A$ an idempotent $n$ by $n$ matrix with entries in $R$. Is the trace of $A$ necessarily a sum of idempotents of $R$?
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0answers
21 views

Extending a trace on algebra to a trace of systems of algebras

Suppose, we have a trace $\tau$ on some algebra $\mathcal{A}$, i.e. $$\tau(aA+bB)=a\tau(A)+b\tau(B)\ \forall A,B\in\mathcal{A}, \forall a,b\in\mathbb{C}$$ The question rises, what are then the ...
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2answers
70 views

Derivative of the trace of $X^TP^TPX$ with respect to P

$\newcommand{\Tr}{\operatorname{Tr}}$ Consider the following expression: $\Tr(X^TP^TPX)$ where $X$ and $P$ are real matrices. What is the best way to approach the calculation of its derivative ...
0
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1answer
81 views

Characterize matrices A such that trace(AC)=0 for every matrix C with trace(C)=0

$A$ is an $n\times n$ matrix on the field $F$ such that for every $n\times n$ matrix $C$ with $\operatorname{trace}(C)=0$ we have $\operatorname{trace}(AC)=0$. Can we characterize such matrices $A $? ...
4
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1answer
189 views

Trace of symmetric positive semidefinite matrix when diagonalized (as a bilinear form) in a non-orthogonal basis

Let $\mathbf{S}$ be symmetric positive semidefinite matrix (i.e. one with all eigenvalues real and non-negative). Then there is an orthogonal matrix $\mathbf{U}$ (with its columns forming an ...
5
votes
1answer
165 views

solving equation also involving unknown matrix in trace

Given two real $m$ x $k$ matrices $A_1$ and $B_1$ and two $k$ x $k$ real matrices $A_2$ and $B_2$ I want to solve the following equation for $Q$. $Q$ is an orthogonal matrix, i.e. $Q^TQ=I$. ...
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1answer
67 views

Trace of power of stochastic matrix

I would like to know if this statement is true. Having a stochastic matrix (rows sum up to 1), with a positive (non-negative) diagonal, then it holds that $$\text{trace}({W^2})\leq ...
1
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1answer
50 views

Trace-zero functions in $W^{1,p}$

This is an excerpt of a textbook's proof for a theorem (Trace-zero functions in $W^{1,p}$), from PDE Evans, 2nd edition, page 275. Next let $\zeta \in C^\infty(\mathbb{R}_+)$ satisfy $$\zeta ...
2
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2answers
87 views

The trace of an operator

My question is derived from A. Deitmar's book: A First Course in Harmonic Analysis (second edition), p22, Exercise 1.17. Let me rewrite it again: Let $k:\mathbb{R}^2 \rightarrow \mathbb{C}$ be smooth ...
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1answer
43 views

Linear Algebra Question concerning the trace of a symmetric positive definite matrix.

The objective is to minimize the diagonal elements of a symmetric positive definite matrix. The expression of this matrix is a little bit nasty and its inverse is much easier to deal with. Can I claim ...
4
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1answer
57 views

Trace Theorem question

From PDE Evans, page 272. My question is towards the bootom of this post. THEOREM 1 (Trace Theorem). Assume $U$ is bounded and $\partial U$ is $C^1$. Then there exists a bounded linear operator ...
2
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1answer
56 views

If a series converges, does it converge with additional log term multiplied?

If $\sum_{n} |a_n| < \infty$, is it true that $\sum_{n} |a_n\log(a_n)| < \infty$ if $0 \leq a_n \leq 1$? I am trying to see if $A$ is trace class operator, then $A \log(A)$ is also trace class ...
2
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1answer
85 views

Norm of symmetric positive semidefinite matrices

I have been researching a lot trying to find an answer to my question and didn't find any so I would appreciate it if anyone can help. If we have 2 symmetric, positive semi-definite matrices $A$ and ...
1
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2answers
132 views

trace of product of a diagonal and a matrix

I would like to know if anything can be said about the trace of a product of two matrices, where one matrix is a diagonal matrix, i.e., $$\text{trace}(DA)=...$$ Are there some bounds in terms of ...
4
votes
2answers
82 views

Determinant and trace as conjugations?

For real matrices $A$ it holds that $$\det\,\big(e^A\big)=e^{\mathrm{tr}\,A}$$ so we can write $$\mathrm{tr}=(\exp)^{-1}\circ \;\det\;\circ\;(\exp).$$ Is this interpretation of trace as the ...
4
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3answers
96 views

Prove that $A$ is diagonalizable iff $\mbox{tr} A\neq 0$

Prove that $A$ is diagonalizable if and only if $\mbox{tr} A\neq 0$. $A$ is an $n\times n$ matrix over $\mathbb{C}$, and $\mbox{rk} A=1$. If $p(t)$ is the characteristic polynomial of $A$, I know ...
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2answers
34 views

trace function ($2\times2$) with ordered bases as linear transformation

We got trace function as following: $$\operatorname{tr}\begin{pmatrix} a & b\\ c & d\\ \end{pmatrix}=a+d$$ So now have to write down $[\operatorname{tr}]_{S_1,S_2}$, ...
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2answers
57 views

A question on Rank and trace of a special matrix [closed]

I want to share the following question which was asked in a competitive exam: For a fixed positive integer $n\geq 3$, let $A$ be the $n\times n$ matrix defined by $A=I-\dfrac{1}{n}J$, where $J$ is ...
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3answers
81 views

Prove or disprove that trace of matrix $X$ is zero

I was trying to solve a question from a competitive exam paper. This is a part of that question. Let $I_n$ and $O_n$ be $n\times n$ identity and null matrices respectively.Let $S$ be $2n\times ...
1
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1answer
71 views

Trace of the exterior power as a determinant

Let $A$ be a matrix. According to Wikipedia, $$tr(\wedge^k A) = \frac{1}{k!} \det \begin{pmatrix} tr (A) & k-1 & 0 & \cdots \\ tr (A^2) & tr (A) & k-2 & \cdots \\ \cdots & ...
2
votes
1answer
64 views

Proof that frobenius norm is a norm [duplicate]

It's pretty basic and I'm sure I'm missing something dumb here, but I'd like to know why $||A+B||_F \leq ||A||_F+||B||_F$ The way I understand it, ...
0
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0answers
13 views

Connes trace doubt and operator $ H=xp$

i am trying to understand the paper from page 315 and on http://www.alainconnes.org/docs/bookwebfinal.pdf a) in the form of a sum of primes what does the integral $$ \int _{Q_{p}} ...
2
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0answers
37 views

Formula for trace of particular operators

Let $\mathcal{H}$ be the Hilbert space $L^2(\mathbb{R})$. View the Fourier transform as a unitary operator $\mathcal{F} \in B(\mathcal{H})$. For each function $f \in C_0(\mathbb{R})$, let $T(f) \in ...
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0answers
12 views

Matrix calculus: rules for partial traces

I'm trying to understand a paper and have trouble seeing why the following can be written: $Tr_E\{[ \rho,V] \} = \sigma Tr_E\{\rho_E V\} - Tr_E\{ V \rho_E \} \sigma$, when we know the following ...
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0answers
67 views

optimization problem minimizing trace of a matrix with inverse

I am trying to solve the following problem $\min_{T} \operatorname{trace} \left( A(T^T M T + N)^{-1}A^T\right)$, where $T$ is the matrix I am solving for and $A$ is given, $M\succ0$ and $N\succ0$. ...
1
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0answers
49 views

trace of a product of similar matrices

I have two known types of matrices, $$L_j= \left[ \begin{matrix} 1 & 1 \\ f_j & -f_j \end{matrix} \right]$$ and $$P_j= \left[ \begin{matrix} e^{i a_j k_j} & 0 \\ 0 & e^{-i a_j k_j} ...
0
votes
1answer
36 views

Linear Algebra,Conjugate Transpose

Let $ M_n(\mathbb C) $ be the space of all $ n\times n $ matrices with complex entries. Prove that function $ \langle, \rangle : M_n(\mathbb C) \times M_n(\mathbb C) \to \mathbb C $ defined by $ ...
0
votes
1answer
102 views

Matrix-Trace and Conjugate Transpose (Multiple Choice)

I was trying to solve the following problem from a competitive exam paper. Let $A=( a_{ij})$ be a nXn complex matrix and let $A^*$ denote the conjugate transpose of $A$. Then which of the following ...