Archive for October 2002
I discuss several issues about the irreversibility of the RG flow and the trace anomalies $c$, $a$ and $a’$. First I argue that in quantum field theory: $i$) the scheme-invariant area $\Delta a’$ of the graph of the effective beta function between the fixed points defines the length of the RG flow; $ii$) the minimum of $\Delta a’$ in the space of flows connecting the same UV and IR fixed points defines the (oriented) distance between the fixed points; $iii$) in even dimensions, the distance between the fixed points is equal to $\Delta a =a_{UV}-a_{IR}$. In even dimensions, these statements imply the inequalities $0 \leq \Delta a \leq \Delta a’$ and therefore the irreversibility of the RG flow. Another consequence is the inequality $a \leq c$ for free scalars and fermions (but not vectors), which can be checked explicitly. Secondly, I elaborate a more general axiomatic set-up where irreversibility is defined as the statement that there exist no pairs of non-trivial flows connecting interchanged UV and IR fixed points. The axioms, based on the notions of length of the flow, oriented distance between the fixed points and certain “oriented-triangle inequalities”, imply the irreversibility of the RG flow without a global a function. I conjecture that the RG flow is irreversible also in odd dimensions (without a global a function). In support of this, I check the axioms of irreversibility in a class of $d=3$ theories where the RG flow is integrable at each order of the large $N$ expansion.
Class.Quant.Grav. 21 (2004) 29-50 | DOI: 10.1088/0264-9381/21/1/003
I study some classes of RG flows in three dimensions that are classically conformal and have manifest $g \rightarrow 1/g$ dualities. The RG flow interpolates between known (four-fermion, Wilson-Fischer, $\phi_3^6$) and new interacting fixed points. These models have two remarkable properties: $i$) the RG flow can be integrated for arbitrarily large values of the couplings g at each order of the $1/N$ expansion; $ii$) the duality symmetries are exact at each order of the $1/N$ expansion. I integrate the RG flow explicitly to the order ${\cal O}(1/N)$, write correlators at the leading-log level and study the interpolation between the fixed points. I examine how duality is implemented in the regularized theory and verified in the results of this paper.
Nucl.Phys. B658 (2003) 440 | DOI: 10.1016/S0550-3213(03)00174-3
Search this site
YouTube Channel
Quantum Gravity 
Book
14B1 D. Anselmi
Renormalization
Course on renormalization, taught in 2015.
Last update: September 15th 2023, 242 pages
The final (2023) edition is vaibable on Amazon:
Contents:
Preface
1. Functional integral
2. Renormalization
3. Renormalization group
4. Gauge symmetry
5. Canonical formalism
6. Quantum electrodynamics
7. Non-Abelian gauge field theories
Notation and useful formulas
References
The pdf file of the 2015 Edition is available here: PDF
Logo
Cite papers of this site as follows:
Auths, Title, 'year'A'num' Renorm
For example:
D. Anselmi, Master functional and proper formalism for quantum gauge field theory, 12A3 Renorm
Cite books as
Auths, Title, 'year'B'num' Renorm
Cite reviews as
Auths, Title, 'year'R'num' Renorm
Cite proceedings as
Auths, Title, 'year'P'num' Renorm
Cite theorems as
Auths, Title, Theorem 'year'T'num' Renorm
Cite exercises as
Auths, Title, Exercise 'year'E'num' Renorm
You may also want to add links as shown
