631 research outputs found
Sigma models with singularities in Euclidean spacetime of dimension 0<=D<4 and in the limit N->infinity
For the case of the single-O()-vector linear sigma models the critical
behaviour following from any singularity in the action is worked out in
the double scaling limit , , . After an exact elimination of Gaussian degrees of freedom, the
critical objects such as coupling constants, indices and susceptibility matrix
are derived for all and spacetime dimensions . There appear
exceptional spacetime dimensions where the degree of the singularity
is more strongly constrained than by the renormalizability requirement.Comment: LaTeX, 25 pages, no figure
Double Scaling Limits, Airy Functions and Multicritical Behaviour in O(N) Vektor Sigma Models
O(N) vector sigma models possessing catastrophes in their action are studied.
Coupling the limit N --> infinity with an appropriate scaling behaviour of the
coupling constants, the partition function develops a singular factor. This is
a generalized Airy function in the case of spacetime dimension zero and the
partition function of a scalar field theory for positive spacetime dimension.Comment: 14 pages, LaTe
On the critical behaviour of hermitean f-matrix models in the double scaling limit with f >= 3
An algorithm for the isolation of any singularity of f-matrix models in the
double scaling limit is presented. In particular it is proved by construction
that only those universality classes exist that are known from 2-matrix models.Comment: 24 pages, LaTex, correction of some notation errors and addition of
four reference
The Continuous Series of Critical Points of the Two-Matrix Model at N -> infinity in the Double Scaling Limit
The critical points of the continuous series are characterized by two complex
numbers l_1,l_2 (Re(l_1,l_2)=3) which enters
the string susceptibility constant through gamma = -2/(n-1). The critical
potentials are analytic functions with a convergence radius depending on l_1 or
l_2. We use the orthogonal polynomial method and solve the Schwinger-Dyson
equations with a technique borrowed from conformal field theory.Comment: 24 pages, LaTe
Full phase stabilization of a Yb:fiber femtosecond frequency comb via high-bandwidth transducers
We present full phase stabilization of an amplified Yb:fiber femtosecond
frequency comb using an intra-cavity electro-optic modulator and an
acousto-optic modulator. These transducers provide high servo bandwidths of 580
kHz and 250 kHz for frep and fceo, producing a robust and low phase noise fiber
frequency comb. The comb was self-referenced with an f - 2f interferometer and
phase locked to an ultra-stable optical reference used for the JILA Sr optical
clock at 698 nm, exhibiting 0.21 rad and 0.47 rad of integrated phase errors
(over 1 mHz - 1 MHz) respectively. Alternatively, the comb was locked to two
optical references at 698 nm and 1064 nm, obtaining 0.43 rad and 0.14 rad of
integrated phase errors respectively
Transverse and longitudinal characterization of electron beams using interaction with optical near-fields
We demonstrate an experimental technique for both transverse and longitudinal
characterization of bunched femtosecond free electron beams. The operation
principle is based on monitoring of the current of electrons that obtained an
energy gain during the interaction with the synchronized optical near-field
wave excited by femtosecond laser pulses. The synchronous
accelerating/decelerating fields confined to the surface of a silicon
nanostructure are characterized using a highly focused sub-relativistic
electron beam. Here the transverse spatial resolution of 450 nm and femtosecond
temporal resolution achievable by this technique are demonstrated
Full phase stabilization of a Yb:fiber femtosecond frequency comb via high-bandwidth transducers
Broadband Phase-Noise Suppression in a Yb-Fiber Frequency Comb
We report a simple technique to suppress high frequency phase noise of a
Yb-based fiber optical frequency comb using an active intensity noise servo.
Out-of-loop measurements of the phase noise using an optical heterodyne beat
with a continuous wave (cw) laser show suppression of phase noise by \geq7 dB
out to Fourier frequencies of 100 kHz with a unity-gain crossing of -700 kHz.
These results are enabled by the strong correlation between the intensity and
phase noise of the laser. Detailed measurements of intensity and phase noise
spectra, as well as transfer functions, reveal that the dominant phase and
intensity noise contribution above -100 kHz is due to amplified spontaneous
emission (ASE) or other quantum noise sources.Comment: 4 pages, 3 figure
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