We present a determination of the perturbative QCD (pQCD) coupling using the V+A channel ALEPH
τ
-decay data. The determination involves the double-pinched Borel–Laplace Sum Rules and Finite Energy ...Sum Rules. The theoretical basis is the Operator Product Expansion (OPE) of the V+A channel Adler function in which the higher order terms of the leading-twist part originate from a model based on the known structure of the leading renormalons of this quantity. The applied evaluation methods are contour-improved perturbation theory (CIPT), fixed-order perturbation theory (FOPT), and Principal Value of the Borel resummation (PV). All the methods involve truncations in the order of the coupling. In contrast to the truncated CIPT method, the truncated FOPT and PV methods account correctly for the suppression of various renormalon contributions of the Adler function in the mentioned sum rules. The extracted value of the
MS
¯
coupling is
α
s
(
m
τ
2
)
=
0.3116
±
0.0073
α
s
(
M
Z
2
)
=
0.1176
±
0.0010
for the average of the FOPT and PV methods, which we regard as our main result. On the other hand, if we include in the average also the CIPT method, the resulting values are significantly higher,
α
s
(
m
τ
2
)
=
0.3194
±
0.0167
α
s
(
M
Z
2
)
=
0.1186
±
0.0021
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Approximate knowledge of the renormalon structure of the Bjorken polarised sum rule (BSR) Γ‾1p−n(Q2) leads to the corresponding BSR characteristic function that allows us to evaluate the ...leading-twist part of BSR. In our previous work 1, this evaluation (resummation) was performed using perturbative QCD (pQCD) coupling a(Q2)≡αs(Q2)/π in specific renormalisation schemes. In the present paper, we continue this work, by using instead holomorphic couplings a(Q2)↦A(Q2) that have no Landau singularities and thus require, in contrast to the pQCD case, no regularisation of the resummation formula. The D=2 and D=4 terms are included in the Operator Product Expansion (OPE) of inelastic BSR, and fits are performed to the available experimental data in a specific interval (Qmin2,Qmax2) where Qmax2=4.74GeV2. We needed relatively high Qmin2≈1.7GeV2 in the pQCD case since the pQCD coupling a(Q2) has Landau singularities at Q2≲1GeV2. Now, when holomorphic (AQCD) couplings A(Q2) are used, no such problems occur: for the 3δAQCD and 2δAQCD variants the preferred values are Qmin2≈0.6GeV2. The preferred values of αs in general cannot be unambiguously extracted, due to large uncertainties of the experimental BSR data. At a fixed value of αsMS‾(MZ2), the values of the D=2 and D=4 residue parameters are determined in all cases, with the corresponding uncertainties.
Manosalva reconoce que el diálogo que él descubre en la prensa católica que selecciona para su análisis es mucho más amplio, pero, para los efectos de una monografía universitaria de posgraduación, ...fueron más que suficientes. Es un libro bien escrito, pulcro, con preocupaciones teóricas y con vasta historiografía. Tres capítulos lo conforman: trabajo, trabajadores y ocio. Todos interesantes, empero, en el del medio, en el de los trabajadores, está su fortaleza. Es el más sólido, el autor se siente más cómodo allí porque se ajusta a su interés y formación teórica. Iglesia y política, Iglesia y Colombia son temáticas de identificación nacional. ¡Que siga el diálogo!
Offering a comprehensive overview of Puerto Rico's history and evolution since the installation of U.S. rule, Cesar Ayala and Rafael Bernabe connect the island's economic, political, cultural, and ...social past.Puerto Rico in the American Centuryexplores Puerto Ricans in the diaspora as well as the island residents, who experience an unusual and daily conundrum: they consider themselves a distinct people but are part of the American political system; they have U.S. citizenship but are not represented in the U.S. Congress; and they live on land that is neither independent nor part of the United States.Highlighting both well-known and forgotten figures from Puerto Rican history, Ayala and Bernabe discuss a wide range of topics, including literary and cultural debates and social and labor struggles that previous histories have neglected. Although the island's political economy remains dependent on the United States, the authors also discuss Puerto Rico's situation in light of world economies. Ayala and Bernabe argue that the inability of Puerto Rico to shake its colonial legacy reveals the limits of free-market capitalism, a break from which would require a renewal of the long tradition of labor and social activism in Puerto Rico in connection with similar currents in the United States.
We apply Borel-Laplace sum rules to the data of the semihadronic tau decay rate. For the higher order terms of the Adler function in the leadingtwist (
D
= 0) contribution we use a ...renormalon-motivated model, where the correct leading anomalous dimensions are taken into account in the IR
u
= 3 (and
u
= 2) renormalon contributions. In the evaluation of
D
= 0 contribution of the sum rules we apply two methods: (a) fixed order perturbation theory (FO) and (b) Borel resummation of the singular part with the Principal Value prescription (PV). We use as data the ALEPH data for the (V+A)-channel, and a combined set of data for the V-channel. In the
D
= 6 OPE term of the Adler function we account for the leading nonzero (and noninteger) anomalous dimension. In the OPE for the Adler function we include terms with dimension up to
D
= 10 for the (V+A)-channel, and up to
D
= 14 for the V-channel. In such cases, the extracted values of the coupling
α
s
and of the condensates show a reasonably good convergence under the increase of OPE terms. In order to suppress the quark-hadron duality violations, our sum rules are doubly-pinched in the Minkowskian point. We obtain the averaged extracted values of the coupling
α
s
(
m
2
τ
) = 0.3169
+0.0070
-0.0096
, corresponding to
α
s
(
M
2
Z
) = 0.1183
+0.0009
-0.0012
.
Butterflies are one of the most recognized and useful groups for the monitoring and establishment of important conservation areas and management policies. In the present study, we estimate the ...richness and diversity, as well as the association value of submontane scrub, oak forest, and cloud forest species at Cerro Bufa El Diente, within the Sierra de San Carlos priority land region, located in the Central-western region of Tamaulipas, Mexico. Three sampling sites were established based on criteria of vegetation distribution per altitudinal floor. One site for each altitudinal floor and vegetation type. Sampling was carried out in permanent transects on a monthly basis at each site, using an aerial entomological net and ten Van Someren-Rydon traps, during four sampling periods: early dry season, late dry season, early wet season and late wet season. In total, 7,611 specimens belonging to six families, 20 subfamilies, 32 tribes, 148 genera and 243 species of the study area were collected. Nymphalidae was the most abundant family with 3,454 specimens, representing 45.38% of total abundance in the study area. Lower abundance was recorded in Hesperiidae (19.17%), Pieridae (16.41%), Lycaenidae (10.17%), Papilionidae (5.12%), and finally Riodinidae (3.74%). The highest species richness was presented in the family Hesperiidae with 34.57% of the total obtained species followed by Nymphalidae (30.45%), Lycaenidae (15.23%), Pieridae (9.88%), Papilionidae (5.76%), and Riodinidae (4.12%). Twenty-seven species were categorized as abundant, these species,
(Guérin-Méneville, 1844),
(Strecker, 1878),
(Linnaeus, 1767),
(Ménétriés, 1857) and
(Boisduval, 1836) presented the highest number of specimens. Sixty-five species were considered common, constituting 41.73% of the total number of butterflies, 63 frequent (9.76% of the total abundance), 55 limited (2.54%) and 33 rare (0.43%). The greatest number of specimens and species, as well as alpha diversity, were presented on the lowest altitudinal floor, made up of submontane scrub, and decreased significantly with increasing altitude. According to the cluster analysis, low and intermediate altitude sites constitute an area of distribution of species that prefer tropical conditions, while the third-floor site forms an independent group of high mountain species. The greatest abundance and richness of species, as well as alpha diversity, was obtained during the last wet season, decreasing significantly towards the early dry season. Moreover, through the use of the association value, 19 species were designated as indicators, three for the last altitudinal floor, three for the intermediate and 13 for the first. The present work represents the first report of the altitudinal variation in richness, abundance and diversity of butterflies in the northeast of Mexico. These results highlight the importance of the conservation of this heterogeneous habitat and establish reference data for the diurnal Lepidoptera fauna of the region.
La poesía de los miembros del grupo Cántico de Córdoba se apartó significativamente de las dos corrientes principales de creación vigentes durante los años 40 y 50 en España. Este distanciamiento ...voluntario provocó que la atención de la crítica y la academia fuese escasa y poco rigurosa hasta que, en 1976, Guillermo Carnero publica su ya clásico estudio del grupo. Sin embargo, este trabajo apunta a que la reivindicación de los poetas de Cántico comienza unos años antes, en Málaga, en lo que sería la antesala de un más que justo reconocimiento plasmado años después de manera general con su incorporación plena al canon literario.
We use the known renormalon structure of Bjorken polarised sum rule (BSR) Γ‾1p−n(Q2) to evaluate the leading-twist part of that quantity. In addition, we include D=2 and D=4 Operator Product ...Expansion (OPE) terms and fit this expression to available experimental data for inelastic BSR. Since we use perturbative QCD (pQCD) coupling, which fails at low squared spacelike momenta Q2≲1GeV2 due to Landau singularities, the fit is performed for Q2≥Qmin2 where Qmin2≈(1.7±0.3)GeV2. Due to large BSR experimental uncertainties, the extracted value of the pQCD coupling has very large uncertainties, especially when Qmin2 is varied. However, when we fix the pQCD coupling to the known world average values, the D=2 and D=4 residue parameters can be determined within large but reasonable uncertainties.
Abstract
We perform numerical analysis of double-pinched Borel–Laplace QCD sum rules for the strangeless semihadronic
τ
-decay data. The
D
= 0 contribution to the theoretical contour integral in the ...sum rules is evaluated by the (truncated) Fixed Order perturbation theory method (FO) and by the Principal Value (PV) of the Borel integration. We use for the full Adler function the operator product expansion (OPE) with the terms ∼〈
O
D
〉 of dimension
D
= 2
n
where 2 ≤
n
≤ 5 for the (V+A)-channel, and 2 ≤
n
≤ 7 for the V-channel data. In our previous works Ayala, Cvetič and Teca (2021,
Eur. Phys. J. C
81
930), Ayala, Cvetič and Teca (2022,
Eur. Phys. J. C
82
362), only the (V+A)-channel data was analysed. In this work, the analysis of a new set of V-channel data is performed as well. Further, a renormalon-motivated construction of the
D
= 0 part of the Adler function is improved in the
u
= 3 infrared renormalon sector, by involving the recently known information on the two principal noninteger values
k
(
j
)
=
γ
(
1
)
(
O
6
(
j
)
)
/
β
0
of the effective leading-order anomalous dimensions. Additionally, the OPE of the Adler function has now the
D
= 6 contribution with the principal anomalous dimension (
∼
α
s
k
(
1
)
), and terms of higher dimension (with zero anomalous dimension). Cross-checks of the obtained extracted values of
α
s
and of the condensates were performed by reproduction of the (central) experimental values of several double-pinched momenta
a
(2,
n
)
. The averaged final extracted values of the (
MS
¯
) coupling are:
α
s
(
m
τ
2
)
=
0.3169
−
0.0096
+
0.0070
, corresponding to
α
s
(
M
Z
2
)
=
0.1183
−
0.0012
+
0.0009
.
Posición socioeconómica, discriminación y color de piel en México Ortiz Hernández, Luis; Pérez-Salgado, Diana; Ayala-Guzmán, César Iván
Perfiles latinoamericanos : revista de la Sede Académica de México de la Facultad Latinoamericana de Ciencias Sociales,
2018, Letnik:
26, Številka:
51
Journal Article
Recenzirano
Odprti dostop
Este artículo documenta las diferencias en posición socioeconómica, experiencias de discriminación y autopercepción de acuerdo al color de piel en adultos mexicanos, considerando que esta última es ...un reflejo del fenotipo simbólicamente vinculado al ancestro geográfico (i. e., indígena, africano o europeo). La premisa es que en la sociedad mexicana prevalece una asociación de lo europeo con rasgos positivos (i. e., “privilegio blanco”) y lo africano e indígena con aspectos negativos, lo cual deriva en prácticas racistas. Con ese fin se analizó la Encuesta Nacional sobre Discriminación en México. Los resultados indican que, con excepciones, los blancos acceden más a la educación, se ubican en mejores ocupaciones, tienen salarios mayores, con menos frecuencia han experimentado discriminación y les gusta más su piel. Conforme la piel es más oscura, la situación es opuesta.
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