4,408 research outputs found
How effective are rewards programs in promoting payment card usage? Empirical evidence
Card issuers have mainly relied on rewards programs as their main strategic driver to increase electronic payments. However, there is scarce evidence on the effectiveness of rewards programs. This paper offers novel evidence on two key issues: i) it measures the impact of rewards programs on the use of payment cards; and ii) it quantifies their economic impact in terms of the cash substitution. The results show that rewards may significantly modify preferences for card payments, their economic impact vary significantly across types of rewards and merchant activities and rewards seem to be more effective on average for debit cardholders. JEL Classification: G20, D12, E41cardholders, merchants, payment cards, preferences, rewards
Bulk Fermions in Warped Models with a Soft Wall
We study bulk fermions in models with warped extra dimensions in the presence
of a soft wall. Fermions can acquire a position dependent bulk Dirac mass that
shields them from the deep infrared, allowing for a systematic expansion in
which electroweak symmetry breaking effects are treated perturbatively. Using
this expansion, we analyze properties of bulk fermions in the soft wall
background. These properties include the realization of non-trivial boundary
conditions that simulate the ones commonly used in hard wall models, the
analysis of the flavor structure of the model and the implications of a heavy
top. We implement a soft wall model of electroweak symmetry breaking with
custodial symmetry and fermions propagating in the bulk. We find a lower bound
on the masses of the first bosonic resonances, after including the effects of
the top sector on electroweak precision observables for the first time, of
m_{KK} \gtrsim 1-3 TeV at the 95% C.L., depending on the details of the Higgs,
and discuss the implications of our results for LHC phenomenology.Comment: 34 pages, 8 figure
Comment on "Two Phase Transitions in the Fully frustrated XY Model"
The conclusions of a recent paper by Olsson (Phys. Rev. Lett. 75, 2758
(1995), cond-mat/9506082) about the fully frustrated XY model in two dimensions
are questioned. In particular, the evidence presented for having two separate
chiral and U(1) phase transitions are critically considered.Comment: One page one table, to Appear in Physical Review Letter
Electroweak constraints on warped models with custodial symmetry
It has been recently argued that realistic models with warped extra
dimensions can have Kaluza-Klein particles accessible at the Large Hadron
Collider if a custodial symmetry, SU(2)_V \times P_{LR}, is used to protect the
T parameter and the coupling of the left-handed bottom quark to the Z gauge
boson. In this article we emphasize that such a symmetry implies that the loop
corrections to both the T parameter and the Z b_L \bar{b}_L coupling are
calculable. In general, these corrections are correlated, can be sizable, and
should be considered to determine the allowed parameter space region in models
with warped extra dimensions and custodial symmetry, including Randall-Sundrum
models with a fundamental Higgs, models of gauge-Higgs unification and
Higgsless models. As an example, we derive the constraints that arise on a
representative model of gauge-Higgs unification from a global fit to the
precision electroweak observables. A scan over the parameter space typically
leads to a lower bound on the Kaluza-Klein excitations of the gauge bosons of
about 2-3 TeV, depending on the configuration. In the fermionic sector one can
have Kaluza-Klein excitations with masses of a few hundred GeV. We present the
constraints on these light fermions from recent Tevatron searches, and explore
interesting discovery channels at the LHC.Comment: 38 pages, 8 figure
Heavy Quarks Above the Top at the Tevatron
Recent developments in models with warped extra dimensions have opened new
possibilities for vector-like quark studies at hadron colliders. These new
vector-like quarks can mix sizably with light Standard Model quarks without
violating low energy constraints. We perform a model-independent analysis to
determine the Tevatron reach in the search for new quarks. We find that the
Tevatron has great potential to observe such quarks via their electroweak
single production due to their mixing with valence quarks. With 4 (8) fb-1
integrated luminosity, one may reach a 5\sigma statistical significance for a
heavy quark of mass 580 (630) GeV if the heavy quark-Standard Model quark
mixing parameter is order one.Comment: Version published in Phys. Rev. D; 19 pages, 4 figures; extended
version including model building example; added Table
Ornithodoros quilinensis sp. nov. (Acari, Argasidae), a new tick species from the Chacoan region in Argentina
Ornithodoros quilinensis sp. nov. (Acari: Argasidae) is described from larvae collected on the small rodents Graomys centralis (Cricetidae: Sigmodontinae) in Argentina. The diagnostic characters for this new species are a combination of small size (520-540 μm), a dorsal plate oval in shape with a length of approximately 200 μm, 14 pairs of dorsal setae, hypostome short and narrower at the base (length from Ph1 to apex 133 μm (120-141)) with dental formula 2/2 and apex blunt, and the capsule of the Haller's organ irregular in shape and without reticulations. The analysis of the 16S rDNA sequences available for the genus Ornithodoros indicate that, phylogenetically, O. quilinensis represents an independent lineage only related to a Bolivian tick species of the genus Ornithodoros yet not formally described.Fil: Venzal, José M.. Universidad de la Republica, Salto; UruguayFil: Nava, Santiago. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; ArgentinaFil: Mangold, Atilio Jose. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; ArgentinaFil: Mastropaolo, Mariano. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; ArgentinaFil: Casás, Gustavo. UNIVERSIDAD DE LA REPUBLICA (UDELAR); . Universidad de la República; UruguayFil: Guglielmone, Alberto Alejandro. Instituto Nacional de Tecnología Agropecuaria Eea, Rafaela; Argentin
Reinstatement of rhipicephalus (Boophilus) australis (Acari: Ixodidae) with redescription of the adult and larval stages
Rhipicephalus australis Fuller, the Australian cattle tick, is reinstated and the adults and larvae redescribed from material collected in Australia. This long ignored boophilid was previously known as R. microplus Canestrini for specimens reported in Australia and New Caledonia. The adults of R. australis are easily recognized by a combination of characters, such as the ventro-medial spurs in the palpal segments of the male, and the abundant, plumose, pale white setae on the dorsum of the female. Other details, such as coxal and adanal shields are more variable among different populations and may lead to incorrect determinations. Larvae of R. australis are clearly smaller than those of R. microplus. The use of principal components analysis on body measurements leads to a clear separation of larvae of both taxa. A phylogenetic analysis based on 12S- and 16S-rDNA gene sequences supports the conspecificity of the neotype material on which the reinstatement of the species is proposed, and of the specimens used for previous interspecific crosses. R. australis is now known to be present in Australia, New Caledonia, the island of Borneo, Philippines, Sumatra, Java, New Guinea, Cambodia, and Tahiti. Both R. microplus and R. australis coexist in some countries in southeastern Asia. Given the extreme importance of these ticks for the cattle industry, field data on their distribution in the region are required to know the actual range of these species and to understand the evolution of the group.Fil: Estrada Peña, Agustín. Universidad de Zaragoza; EspañaFil: Venzal, José M.. Universidad de la República; UruguayFil: Nava, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Mangold, Atilio Jose. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Guglielmone, Alberto Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Labruna, Marcelo B.. Universidade de Sao Paulo; BrasilFil: de la Fuente, José. Instituto de Investigación en Recursos Cinegéticos; Españ
Unconventional cosmology on the (thick) brane
We consider the cosmology of a thick codimension 1 brane. We obtain the
matching conditions leading to the cosmological evolution equations and show
that when one includes matter with a pressure component along the extra
dimension in the brane energy-momentum tensor, the cosmology is of non-standard
type. In particular one can get acceleration when a dust of non-relativistic
matter particles is the only source for the (modified) Friedman equation. Our
equations would seem to violate the conservation of energy-momentum from a 4D
perspective, but in 5D the energy-momentum is conserved. One could write down
an effective conserved 4D energy-momentum tensor attaching a ``dark energy''
component to the energy-momentum tensor of matter that has pressure along the
extra dimension. This extra component could, on a cosmological scale, be
interpreted as matter-coupled quintessence. We comment on the effective 4D
description of this effect in terms of the time evolution of a scalar field
(the 5D radion) coupled to this kind of matter.Comment: 9 pages, v2. eq.(17) corrected, comments on effective theory change
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