Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
3,280
result(s) for
"Russo, G."
Sort by:
Nonlinear electrodynamics without birefringence
A
bstract
All solutions of the no-birefringence conditions for nonlinear electrodynamics are found. In addition to the known Born-Infeld and Plebanski cases, we find a “reverse Born-Infeld” case, which has a limit to Plebanski, and an “extreme-Born-Infeld” case, which arises as a Lagrangian constraint. Only Born-Infeld has a weak-field limit, and only Born-Infeld and extreme-Born-Infeld avoid superluminal propagation in constant electromagnetic backgrounds, but all cases have a conformal strong-field limit that coincides with the strong-field limit of Born-Infeld found by Bialynicki-Birula.
Journal Article
Thermal correlation functions in CFT and factorization
A
bstract
We study 2-point and 3-point functions in CFT at finite temperature for large dimension operators using holography. The 2-point function leads to a universal formula for the holographic free energy in
d
dimensions in terms of the
c
-anomaly coefficient. By including
α
′ corrections to the black brane background, we reproduce the leading correction at strong coupling. In turn, 3-point functions have a very intricate structure, exhibiting a number of interesting properties. In simple cases, we find an analytic formula. When the dimensions satisfy ∆
i
= ∆
j
+ ∆
k
, the thermal 3-point function satisfies a factorization property. We argue that in
d >
2 factorization is a reflection of the semiclassical regime.
Journal Article
Large N correlation functions in superconformal field theories
A
bstract
We compute correlation functions of chiral primary operators in
N
=
2
super-conformal theories at large
N
using a construction based on supersymmetric localization recently developed by Gerchkovitz et al. We focus on
N
=
4
SYM as well as on supercon-formal QCD. In the case of
N
=
4
we recover the free field theory results as expected due to non-renormalization theorems. In the case of superconformal QCD we study the planar expansion in the large
N
limit. The final correlators admit a simple generalization to a finite
N
formula which exactly matches the various small
N
results in the literature.
Journal Article
Defects in scalar field theories, RG flows and dimensional disentangling
A
bstract
We consider defect operators in scalar field theories in dimensions
d
= 4 −
ϵ
and
d
= 6 −
ϵ
with self-interactions given by a general marginal potential. In a double scaling limit, where the bulk couplings go to zero and the defect couplings go to infinity, the bulk theory becomes classical and the quantum defect theory can be solved order by order in perturbation theory. We compute the defect
β
functions to two loops and study the Renormalization Group flows. The defect fixed points can move and merge, leading to fixed point annihilation; and they exhibit a remarkable factorization property where the
c
-dependence gets disentangled from the coupling dependence.
Journal Article
Deformed Cauchy random matrix ensembles and large N phase transitions
A
bstract
We study a new hermitian one-matrix model containing a logarithmic Penner’s type term and another term, which can be obtained as a limit from logarithmic terms. For small coupling, the potential has an absolute minimum at the origin, but beyond a certain value of the coupling the potential develops a double well. For a higher critical value of the coupling, the system undergoes a large
N
third-order phase transition.
Journal Article
A limit for large R-charge correlators in N = 2 theories
A
bstract
Using supersymmetric localization, we study the sector of chiral primary operators (Tr
ϕ
2
)
n
with large
R
-charge 4
n
in
N
= 2 four-dimensional superconformal theories in the weak coupling regime
g
→ 0, where λ ≡
g
2
n
is kept fixed as
n
→ ∞,
g
representing the gauge theory coupling(s). In this limit, correlation functions
G
2
n
of these operators behave in a simple way, with an asymptotic behavior of the form
G
2
n
≈
F
∞
λ
λ
2
π
e
2
n
n
α
, modulo
O
(1
/n
) corrections, with
α
=
1
2
dim
g
for a gauge algebra
g
and a universal function
F
∞
(λ). As a by-product we find several new formulas both for the partition function as well as for perturbative correlators in
N
=
2
s
u
N
gauge theory with 2
N
fundamental hypermultiplets.
Journal Article
Causality and energy conditions in nonlinear electrodynamics
A
bstract
For the general theory of nonlinear electrodynamics (NLED) we prove that causality implies both the Dominant Energy Condition (DEC) and, surprisingly, the Strong Energy Condition (SEC). This has implications for gravitational applications, such as regular black holes supported by NLED matter. For self-dual NLED theories, weak-field causality alone implies both the DEC and SEC, as we illustrate with Born-Infeld and ModMax electrodynamics.
Journal Article
Simplified self-dual electrodynamics
A
bstract
We present a new formulation of self-dual nonlinear electrodynamics in which interactions are determined by an auxiliary-field potential, with causality ensuring a unique solution to the auxiliary-field equation. The long-standing problem of an explicit Lagrangian for the generic ‘analytic’ theory is simply solved by restriction to potentials that are even functions of the auxiliary field. In this case the Lagrangian can be linearised in quadratic field-strength scalars by the introduction of an additional pseudoscalar auxiliary field; this generalises, to all analytic self-dual theories, a well-known construction of the Born-Infeld theory.
Journal Article
Causal chiral 2-form electrodynamics
A
bstract
Generic nonlinear theories of chiral 2-form electrodynamics allow superluminal propagation in some stationary homogeneous backgrounds and are therefore acausal. We find a simple parameterisation of the Hamiltonian for causal theories, and we use it to show that the stress-energy tensor satisfies both the Dominant and Strong energy conditions. We also revisit the Perry-Schwarz formulation, clarifying aspects of it and of its relation to the Hamiltonian formulation.
Journal Article