202 research outputs found
Vanishing conductivity of quantum solitons in polyacetylene
Quantum solitons or polarons are supposed to play a crucial role in the
electric conductivity of polyacetylene, in the intermediate doping regime. We
present an exact fully quantized calculation of the quantum soliton
conductivity in polyacetylene and show that it vanishes exactly. This is
obtained by applying a general method of soliton quantization, based on
order-disorder duality, to a Z(2)-symmetric complex extension of the TLM
dimerization effective field theory. We show that, in this theory,
polyacetylene solitons are sine-Gordon solitons in the phase of the complex
field.Comment: To appear in J. Phys. A: Math. Theor., 15 page
Pairing and superconductivity in the flat band: Creutz lattice
We use unbiased numerical methods to study the onset of pair superfluidity in
a system that displays flat bands in the noninteracting regime. This is
achieved by using a known example of flat band systems, namely the Creutz
lattice, where we investigate the role of local attractive interactions in the
Hubbard model. Going beyond the standard approach used in these systems
where weak interactions are considered, we map the superfluid behavior for a
wide range of interaction strengths and exhibit a crossover between BCS and
tightly bound bosonic fermion pairs. We further contrast these results with a
standard two-leg fermionic ladder, showing that the pair correlations, although
displaying algebraic decay in both cases, are longer ranged in the Creutz
lattice, signifying the robustness of pairing in this system.Comment: 11 pages, 12 figures; as publishe
Exact Asymptotic Behaviour of Fermion Correlation Functions in the Massive Thirring Model
We obtain an exact asymptotic expression for the two-point fermion
correlation functions in the massive Thirring model (MTM) and show that, for
, they reproduce the exactly known corresponding functions of the
massless theory, explicitly confirming the irrelevance of the mass term at this
point. This result is obtained by using the Coulomb gas representation of the
fermionic MTM correlators in the bipolar coordinate system.Comment: To appear in J. Phys. A: Math. Gen. 12 page
PHYSICAL ACTIVITY FOR MEN WITH CHRONIC PROSTATITIS/ CHRONIC PELVIC PAIN SYNDROME NOT SATISFIED WITH CONVENTIONAL TREATMENTS: COULD IT REPRESENT A VALID OPTION? THE PHYSICAL ACTIVITY AND MALE PELVIC PAIN TRIAL : A DOUBLE BLIND, RANDOMIZED STUDY
Sine-Gordon/Coulomb Gas Soliton Correlation Functions and an Exact Evaluation of the Kosterlitz-Thouless Critical Exponent
We present an exact derivation for the asymptotic large distance behavior of
the spin two-point correlation function in the XY-model. This allows for the
exact obtainment of the critical exponent at the Kosterlitz-Thouless
transition that occurs in this model and in the 2D neutral Coulomb gas and
which has been previously obtained by scaling arguments. In order to do that,
we use the language of sine-Gordon theory to obtain a Coulomb Gas description
of the XY-model spin correlation function, which becomes identified with the
soliton correlator of that theory. Using a representation in terms of bipolar
coordinates we obtain an exact expression for the asymptotic large distance
behavior of the relevant correlator at , which corresponds to the
Kosterlitz-Thouless transition. The result is obtained by approaching this
point from the plasma (high-temperature) phase of the gas. The vortex
correlator of the XY-model is also obtained using the same procedure.Comment: To appear in J. Stat. Phys., 11 page
A rare case of a retroperitoneal enterogenous cyst with in-situ adenocarcinoma
<p>Abstract</p> <p>Background</p> <p>Retroperitoneal enterogenous cysts are uncommon and adenocarcinoma within such cysts is a rare complication.</p> <p>Case presentation</p> <p>We present the third described case of a retroperitoneal enterogenous cyst with adenocarcinomatous changes and only the second reported case whereby the cyst was not arising from any anatomical structure.</p> <p>Conclusion</p> <p>This case demonstrates the difficulties in making a diagnosis as well as the importance of a multi-disciplinary approach, and raises further questions regarding post-operative treatment with chemotherapy.</p
Next-generation laser retroreflectors for GNSS, solar system exploration, geodesy, gravitational physics and earth observation
The SCF_Lab (Satellite/lunar/gnss laser ranging and altimetry Characterization Facility Laboratory) of INFNLNF is designed to cover virtually LRAs (Laser Retroreflector Arrays) of CCRs (Cube Corner Retroreflectors) for missions in the whole solar system, with a modular organization of its instrumentation, two redundant SCF (SCF_Lab Characterization Facilities), and an evolutionary measurement approach, including customization and potentially upgrade on-demand. See http://www.lnf.infn.it/esperimenti/etrusco/ for a general description
The Spherically Symmetric Standard Model with Gravity
Spherical reduction of generic four-dimensional theories is revisited. Three
different notions of "spherical symmetry" are defined. The following sectors
are investigated: Einstein-Cartan theory, spinors, (non-)abelian gauge fields
and scalar fields. In each sector a different formalism seems to be most
convenient: the Cartan formulation of gravity works best in the purely
gravitational sector, the Einstein formulation is convenient for the Yang-Mills
sector and for reducing scalar fields, and the Newman-Penrose formalism seems
to be the most transparent one in the fermionic sector. Combining them the
spherically reduced Standard Model of particle physics together with the
usually omitted gravity part can be presented as a two-dimensional (dilaton
gravity) theory.Comment: 58 pages, 2 eps figure
A dialética em questão: considerações teórico-metodológicas sobre a historiografia contemporânea
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