14,122 research outputs found
Ising Field Theory on a Pseudosphere
We show how the symmetries of the Ising field theory on a pseudosphere can be
exploited to derive the form factors of the spin fields as well as the
non-linear differential equations satisfied by the corresponding two-point
correlation functions. The latter are studied in detail and, in particular, we
present a solution to the so-called connection problem relating two of the
singular points of the associated Painleve VI equation. A brief discussion of
the thermodynamic properties is also presented.Comment: 39 pages, 6 eps figures, uses harvma
Transverse self-modulation of ultra-relativistic lepton beams in the plasma wakefield accelerator
The transverse self-modulation of ultra-relativistic, long lepton bunches in
high-density plasmas is explored through full-scale particle-in-cell
simulations. We demonstrate that long SLAC-type electron and positron bunches
can become strongly self-modulated over centimeter distances, leading to wake
excitation in the blowout regime with accelerating fields in excess of 20 GV/m.
We show that particles energy variations exceeding 10 GeV can occur in
meter-long plasmas. We find that the self-modulation of positively and
negatively charged bunches differ when the blowout is reached. Seeding the
self-modulation instability suppresses the competing hosing instability. This
work reveals that a proof-of-principle experiment to test the physics of bunch
self-modulation can be performed with available lepton bunches and with
existing experimental apparatus and diagnostics.Comment: 8 pages, 8 figures, accepted for publication in Physics of Plasma
On the magnetic perturbation of the Ising model on the sphere
In this letter we will extend the analysis given by Al. Zamolodchikov for the
scaling Yang-Lee model on the sphere to the Ising model in a magnetic field. A
numerical study of the partition function and of the vacuum expectation values
(VEV) is done by using the truncated conformal space (TCS) approach. Our
results strongly suggest that the partition function is an entire function of
the coupling constant.Comment: 8 pages, 1 figure, revised version, references adde
Two-kink bound states in the magnetically perturbed Potts field theory at T<Tc
The q-state Potts field theory with in the low-temperature
phase is considered in presence of a weak magnetic field h. In absence of the
magnetic field, the theory is integrable, but not free at q>2: its elementary
excitations - the kinks - interact at small distances, and their interaction
can be characterized by the factorizable scattering matrix which was found by
Chim and Zamolodchikov. The magnetic field induces the long-range attraction
between kinks causing their confinement into the bound-states. We calculate the
masses of the two-kink bound states in the leading order in |h| -> 0 expressing
them in terms of the scattering matrix of kinks at h=0.Comment: 20 pages, no figures, v2: one section and references adde
R-matrices of three-state Hamiltonians solvable by Coordinate Bethe Ansatz
We review some of the strategies that can be implemented to infer an
-matrix from the knowledge of its Hamiltonian. We apply them to the
classification achieved in arXiv:1306.6303, on three state -invariant
Hamiltonians solvable by CBA, focusing on models for which the -matrix is
not trivial.
For the 19-vertex solutions, we recover the -matrices of the well-known
Zamolodchikov--Fateev and Izergin--Korepin models. We point out that the
generalized Bariev Hamiltonian is related to both main and special branches
studied by Martins in arXiv:1303.4010, that we prove to generate the same
Hamiltonian. The 19-vertex SpR model still resists to the analysis, although we
are able to state some no-go theorems on its -matrix.
For 17-vertex Hamiltonians, we produce a new -matrix.Comment: 22 page
More General Correlation Functions of Twist Fields From Ward Identities in the Massive Dirac Theory
Following on from previous work we derive the non-linear differential
equations of more general correlators of U(1) twist fields in two-dimensional
massive Dirac theory. Using the conserved charges of the double copy model
equations parametrising the correlators of twist fields with arbitrary twist
parameter are found. This method also gives a parametrisation of the
correlation functions of general, fermionic, descendent twist fields. The
equations parametrising correlators of primary twist fields are compared to
those of the literature and evidence is presented to confirm that these
equations represent the correct parametrisation.Comment: 18 pages, 1 figur
Measurement of Magnetic-Field Structures in a Laser-Wakefield Accelerator
Experimental measurements of magnetic fields generated in the cavity of a
self-injecting laser-wakefield accelerator are presented. Faraday rotation is
used to determine the existence of multi-megagauss fields, constrained to a
transverse dimension comparable to the plasma wavelength and several plasma
wavelengths longitudinally. The fields are generated rapidly and move with the
driving laser. In our experiment, the appearance of the magnetic fields is
correlated to the production of relativistic electrons, indicating that they
are inherently tied to the growth and wavebreaking of the nonlinear plasma
wave. This evolution is confirmed by numerical simulations, showing that these
measurements provide insight into the wakefield evolution with high spatial and
temporal resolution
On the Yang-Lee and Langer singularities in the O(n) loop model
We use the method of `coupling to 2d QG' to study the analytic properties of
the universal specific free energy of the O(n) loop model in complex magnetic
field. We compute the specific free energy on a dynamical lattice using the
correspondence with a matrix model. The free energy has a pair of Yang-Lee
edges on the high-temperature sheet and a Langer type branch cut on the
low-temperature sheet. Our result confirms a conjecture by A. and Al.
Zamolodchikov about the decay rate of the metastable vacuum in presence of
Liouville gravity and gives strong evidence about the existence of a weakly
metastable state and a Langer branch cut in the O(n) loop model on a flat
lattice. Our results are compatible with the Fonseca-Zamolodchikov conjecture
that the Yang-Lee edge appears as the nearest singularity under the Langer cut.Comment: 38 pages, 16 figure
- …