14,645 research outputs found
Analysis and interpretation of new low-energy Pi-Pi scattering data
The recently published E865 data on charged K_e4 decays and Pi-Pi phases are
reanalyzed to extract values of the two S-wave scattering lengths, of the
subthreshold parameters alpha and beta, of the low-energy constants l3-bar and
l4-bar as well as of the main two-flavour order parameters: and F_pi
in the limit m_u = m_d = 0 taken at the physical value of the strange quark
mass. Our analysis is exclusively based on direct experimental information on
Pi-Pi phases below 800 MeV and on the new solutions of the Roy equations by
Ananthanarayan et al. The result is compared with the theoretical prediction
relating 2 a_0^0 - 5 a_0^2 and the scalar radius of the pion, which was
obtained in two-loop Chiral Perturbation Theory. A discrepancy at the 1-sigma
level is found and commented upon.Comment: Published version, to appear in Eur. Phys. J.
Deconstructibility and the Hill lemma in Grothendieck categories
A full subcategory of a Grothendieck category is called deconstructible if it
consists of all transfinite extensions of some set of objects. This concept
provides a handy framework for structure theory and construction of
approximations for subcategories of Grothendieck categories. It also allows to
construct model structures and t-structures on categories of complexes over a
Grothendieck category. In this paper we aim to establish fundamental results on
deconstructible classes and outline how to apply these in the areas mentioned
above. This is related to recent work of Gillespie, Enochs, Estrada, Guil
Asensio, Murfet, Neeman, Prest, Trlifaj and others.Comment: 20 pages; version 2: minor changes, misprints corrected, references
update
Schnabl's L_0 Operator in the Continuous Basis
Following Schnabl's analytic solution to string field theory, we calculate
the operators for a scalar field in the
continuous basis. We find an explicit and simple expression for them
that further simplifies for their sum, which is block diagonal in this basis.
We generalize this result for the bosonized ghost sector, verify their
commutation relation and relate our expressions to wedge state representations.Comment: 1+16 pages. JHEP style. Typos correcte
Semiclassical Strings in AdS_5 x S^5 and Automorphic Functions
Using AdS/CFT we derive from the folded spinning string ordinary differential
equations for the anomalous dimension of the dual N=4 SYM twist-two operators
at strong coupling. We show that for large spin the asymptotic solutions have
the Gribov-Lipatov recirocity property. To obtain this result we use a hidden
modular invariance of the energy-spin relation of the folded spinning string.
Further we identify the Moch-Vermaseren-Vogt (MVV) relations, which were first
recognized in plain QCD calculations, as the recurrence relations of the
asymptotic series ansatz.Comment: 4 page
The Goldberger-Treiman Discrepancy
The Golberger- Treiman discrepancy is related to the asymptotic behaviour of
the pionic form factor of the nucleon obtained from baryonic QCD sum rules. The
result is .015<=Delta_{GT}<=.022Comment: References updated and minor correction
Infinite-Randomness Fixed Points for Chains of Non-Abelian Quasiparticles
One-dimensional chains of non-Abelian quasiparticles described by
Chern-Simons-Witten theory can enter random singlet phases analogous to that of
a random chain of ordinary spin-1/2 particles (corresponding to ). For this phase provides a random singlet description of the
infinite randomness fixed point of the critical transverse field Ising model.
The entanglement entropy of a region of size in these phases scales as for large , where is the quantum
dimension of the particles.Comment: 4 pages, 4 figure
Superstring field theory equivalence: Ramond sector
We prove that the finite gauge transformation of the Ramond sector of the
modified cubic superstring field theory is ill-defined due to collisions of
picture changing operators.
Despite this problem we study to what extent could a bijective classical
correspondence between this theory and the (presumably consistent)
non-polynomial theory exist. We find that the classical equivalence between
these two theories can almost be extended to the Ramond sector: We construct
mappings between the string fields (NS and Ramond, including Chan-Paton factors
and the various GSO sectors) of the two theories that send solutions to
solutions in a way that respects the linearized gauge symmetries in both sides
and keeps the action of the solutions invariant. The perturbative spectrum
around equivalent solutions is also isomorphic.
The problem with the cubic theory implies that the correspondence of the
linearized gauge symmetries cannot be extended to a correspondence of the
finite gauge symmetries. Hence, our equivalence is only formal, since it
relates a consistent theory to an inconsistent one. Nonetheless, we believe
that the fact that the equivalence formally works suggests that a consistent
modification of the cubic theory exists. We construct a theory that can be
considered as a first step towards a consistent RNS cubic theory.Comment: v1: 24 pages. v2: 27 pages, significant modifications of the
presentation, new section, typos corrected, references adde
Exact marginality in open string field theory: a general framework
We construct analytic solutions of open bosonic string field theory for any
exactly marginal deformation in any boundary conformal field theory when
properly renormalized operator products of the marginal operator are given. We
explicitly provide such renormalized operator products for a class of marginal
deformations which include the deformations of flat D-branes in flat
backgrounds by constant massless modes of the gauge field and of the scalar
fields on the D-branes, the cosine potential for a space-like coordinate, and
the hyperbolic cosine potential for the time-like coordinate. In our
construction we use integrated vertex operators, which are closely related to
finite deformations in boundary conformal field theory, while previous analytic
solutions were based on unintegrated vertex operators. We also introduce a
modified star product to formulate string field theory around the deformed
background.Comment: 63 pages, 10 figures, LaTeX2
The superconducting gaps in FeSe studied by soft point-contact Andreev reflection spectroscopy
FeSe single crystals have been studied by soft point-contact
Andreev-reflection spectroscopy. Superconducting gap features in the
differential resistance dV/dI(V) of point contacts such as a characteristic
Andreev-reflection double-minimum structure have been measured versus
temperature and magnetic field. Analyzing dV/dI within the extended two-gap
Blonder-Tinkham-Klapwijk model allows to extract both the temperature and
magnetic field dependence of the superconducting gaps. The temperature
dependence of both gaps is close to the standard BCS behavior. Remarkably, the
magnitude of the double-minimum structure gradually vanishes in magnetic field,
while the minima position only slightly shifts with field indicating a weak
decrease of the superconducting gaps. Analyzing the dV/dI(V) spectra for 25
point contacts results in the averaged gap values = 1.8+/-0.4meV and
=1.0+/-0.2 meV and reduced values 2/kTc=4.2+/-0.9 and
2/kTc=2.3+/-0.5 for the large (L) and small (S) gap, respectively.
Additionally, the small gap contribution was found to be within tens of percent
decreasing with both temperature and magnetic field. No signatures in the dV/dI
spectra were observed testifying a gapless superconductivity or presence of
even smaller gaps.Comment: 8 pages, 4 figs., 3 tables. Shortened version without fig.4 and Table
3 is accepted for publication in Phys. Rev.
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