Poder, altruismo y turismo comunitario: Un estudio comparativo

Residents of San Juan La Laguna and San Pedro La Laguna, neighboring towns on the shores of Lake Atitlán, Guatemala, have followed very different trajectories of tourism development despite their close proximity. This study explores residents’ perceptions of the benefits and drawbacks of tourism development under two differing economic models and addresses weaknesses in current theoretical approaches. Findings from this ethnographic comparative case study indicate that prevailing theoretical constructs do not fully explain dynamics in non-western non- laissez faire capitalist contexts. Findings also suggest that strong community collaboration guided by governmental and nongovernmental organizations (NGOs) can help to maintain tourism benefits locally, while at the same time preventing some of the costs of tourism development in destination communities.Los residentes de San Juan La Laguna y San Pedro La Laguna, dos pueblos vecinos en la cuenca del Lago de Atitlán (Guatemala), han seguido trayectorias de desarrollo turístico muy diferentes a pesar de su proximidad. En este estudio se explora las percepciones de los residentes de comunidades bajo diferentes modelos económicos y aborda las debilidades de los enfoques teóricos actuales. Se realiza un estudio comparativo de casos etnográfico, a fin de explorar las percepciones de las residentes respecto a las ventajas e inconvenientes derivadas del desarrollo turístico de sus pueblos. Los hallazgos indican que los prevaleciente constructos teóricos no explican plenamente esta dinámica en contextos no occidentales y que son no practican laissez faire capitalismo. Los resultados también sugieren que la fuerte colaboración comunitaria guiada por organizaciones gubernamentales y no gubernamentales puede ayudar a mantener los beneficios del turismo en las comunidades de destino, mientras que previene algunos de sus costo

Black Hole Scattering from Monodromy

We study scattering coefficients in black hole spacetimes using analytic properties of complexified wave equations. For a concrete example, we analyze the singularities of the Teukolsky equation and relate the corresponding monodromies to scattering data. These techniques, valid in full generality, provide insights into complex-analytic properties of greybody factors and quasinormal modes. This leads to new perturbative and numerical methods which are in good agreement with previous results.Comment: 28 pages + appendices, 2 figures. For Mathematica calculation of Stokes multipliers, download "StokesNotebook" from https://sites.google.com/site/justblackholes/techy-zon

Investment in Cellulosic Biofuel Refineries: Do Waivable Biofuel Mandates Matter?

We develop a conceptual model to study the impact of mandate policies on stimulating investment in cellulosic biofuel refineries. In a two-period framework, we compare the first-period investment level (FIL) under three scenarios: laissez-faire, non-waivable mandate (NWM) policy, and waivable mandate (WM) policy. Results show that when plant-level marginal costs are increasing then both NWM policy and WM policy may stimulate FIL. The WM policy has a smaller impact than does the NWM policy. When the plant-level marginal costs are constants, however, WM policy does not increase FIL but does increase the expected profit of more efficient investors

Localized modes at a D-brane--O-plane intersection and heterotic Alice strings

We study a system of $N_c$ $D3$-branes intersecting $D7$-branes and $O7$-planes in 1+1-dimensions. We use anomaly cancellation and string dualities to argue that there must be chiral fermion zero-modes on the $D3$-branes which are localized near the $O7$-planes. Away from the orientifold limit we verify this by using index theory as well as explicit construction of the zero-modes. This system is related to F-theory on K3 and heterotic matrix string theory, and the heterotic strings are related to Alice string defects in $\mathcal{N}=4$ Super-Yang-Mills. In the limit of large $N_c$ we find an $AdS_3$ dual of the heterotic matrix string CFT.Comment: 44 pages, typos corrected, version published in JHE

alpha'-exact entropies for BPS and non-BPS extremal dyonic black holes in heterotic string theory from ten-dimensional supersymmetry

We calculate near-horizon solutions for four-dimensional 4-charge and five-dimensional 3-charge black holes in heterotic string theory from the part of the ten-dimensional tree-level effective action which is connected to gravitational Chern-Simons term by supersymmetry. We obtain that the entropies of large black holes exactly match the alpha'-exact statistical entropies obtained from microstate counting (D=4) and AdS/CFT correspondence (D=5). Especially interesting is that we obtain agreement for both BPS and non-BPS black holes, contrary to the case of R^2-truncated (four-derivative) actions (D-dimensional N=2 off-shell supersymmetric or Gauss-Bonnet) were used, which give the entropies agreeing (at best) just for BPS black holes. The key property of the solutions, which enabled us to tackle the action containing infinite number of terms, is vanishing of the Riemann tensor \bar{R}_{MNPQ} obtained from torsional connection defined with \bar{\Gamma} = \Gamma - H/2. Morover, if every monomial of the remaining part of the effective action would contain at least two Riemanns \bar{R}_{MNPQ}, it would trivially follow that our solutions are exact solutions of the full heterotic effective action in D=10. The above conjecture, which appeared (in this or stronger form) from time to time in the literature, has controversial status, but is supported by the most recent calculations of Richards (arXiv:0807.3453 [hep-th]). Agreement of our results for the entropies with the microscopic ones supports the conjecture. As for small black holes, our solutions in D=5 still have singular horizons.Comment: 28 pages; v2: minor changes, references added; v3: extended discussion on small black holes in sec. 5.4, more references added, accepted in JHE

D-Brane Propagation in Two-Dimensional Black Hole Geometries

We study propagation of D0-brane in two-dimensional Lorentzian black hole backgrounds by the method of boundary conformal field theory of SL(2,R)/U(1) supercoset at level k. Typically, such backgrounds arise as near-horizon geometries of k coincident non-extremal NS5-branes, where 1/k measures curvature of the backgrounds in string unit and hence size of string worldsheet effects. At classical level, string worldsheet effects are suppressed and D0-brane propagation in the Lorentzian black hole geometry is simply given by the Wick rotation of D1-brane contour in the Euclidean black hole geometry. Taking account of string worldsheet effects, boundary state of the Lorentzian D0-brane is formally constructible via Wick rotation from that of the Euclidean D1-brane. However, the construction is subject to ambiguities in boundary conditions. We propose exact boundary states describing the D0-brane, and clarify physical interpretations of various boundary states constructed from different boundary conditions. As it falls into the black hole, the D0-brane radiates off to the horizon and to the infinity. From the boundary states constructed, we compute physical observables of such radiative process. We find that part of the radiation to infinity is in effective thermal distribution at the Hawking temperature. We also find that part of the radiation to horizon is in the Hagedorn distribution, dominated by massive, highly non-relativistic closed string states, much like the tachyon matter. Remarkably, such distribution emerges only after string worldsheet effects are taken exactly into account. From these results, we observe that nature of the radiation distribution changes dramatically across the conifold geometry k=1 (k=3 for the bosonic case), exposing the `string - black hole transition' therein.Comment: 51 pages, 5 figures, v2: referece added, note added replying the comment made in hep-th/060206

Electrified Fuzzy Spheres and Funnels in Curved Backgrounds

We use the non-Abelian DBI action to study the dynamics of $N$ coincident $Dp$-branes in an arbitrary curved background, with the presence of a homogenous world-volume electric field. The solutions are natural extensions of those without electric fields, and imply that the spheres will collapse toward zero size. We then go on to consider the $D1-D3$ intersection in a curved background and find various dualities and automorphisms of the general equations of motion. It is possible to map the dynamical equation of motion to the static one via Wick rotation, however the additional spatial dependence of the metric prevents this mapping from being invertible. Instead we find that a double Wick rotation leaves the static equation invariant. This is very different from the behaviour in Minkowski space. We go on to construct the most general static fuzzy funnel solutions for an arbitrary metric either by solving the static equations of motion, or by finding configurations which minimise the energy. As a consistency check we construct the Abelian $D3$-brane world-volume theory in the same generic background and find solutions consistent with energy minimisation. In the $NS$5-brane background we find time dependent solutions to the equations of motion, representing a time dependent fuzzy funnel. These solutions match those obtained from the $D$-string picture to leading order suggesting that the action in the large $N$ limit does not need corrections. We conclude by generalising our solutions to higher dimensional fuzzy funnels.Comment: 38 pages, Latex; references adde

Fundamental Superstrings as Holograms

The worldsheet of a macroscopic fundamental superstring in the Green-Schwarz light-cone gauge is viewed as a possible boundary hologram of the near horizon region of a small black string. For toroidally compactified strings, the hologram has global symmetries of AdS_3 \times S^{d-1} \times T^{8-d}, (d =3,..,8), only some of which extend to local conformal symmetries. We construct the bulk string theory in detail for the particular case of d=3. The symmetries of the hologram are correctly reproduced from this exact worldsheet description in the bulk. Moreover, the central charge of the boundary Virasoro algebra obtained from the bulk agrees with the Wald entropy of the associated small black holes. This construction provides an exact CFT description of the near horizon region of small black holes both in Type-II and heterotic string theory arising from multiply wound fundamental superstrings.Comment: 46 pages, JHEP style. v2: Comments, references adde

String Theory on Warped AdS_3 and Virasoro Resonances

We investigate aspects of holographic duals to time-like warped AdS_3 space-times--which include G\"odel's universe--in string theory. Using worldsheet techniques similar to those that have been applied to AdS_3 backgrounds, we are able to identify space-time symmetry algebras that act on the dual boundary theory. In particular, we always find at least one Virasoro algebra with computable central charge. Interestingly, there exists a dense set of points in the moduli space of these models in which there is actually a second commuting Virasoro algebra, typically with different central charge than the first. We analyze the supersymmetry of the backgrounds, finding related enhancements, and comment on possible interpretations of these results. We also perform an asymptotic symmetry analysis at the level of supergravity, providing additional support for the worldsheet analysis.Comment: 24 pages + appendice

Rationalising "for" and "against" a policy of school-led careers guidance in STEM in the U.K. : a teacher perspective

This paper reports on teacher attitudes to changes in the provision of careers guidance in the U.K., particularly as it relates to Science, Technology, Engineering and Mathematics (STEM). It draws on survey data of n = 94 secondary-school teachers operating in STEM domains and their attitudes towards a U.K. and devolved policy of internalising careers guidance within schools. The survey presents a mixed message of teachers recognising the significance of their unique position in providing learners with careers guidance yet concern that their ‘relational proximity’ to students and ‘informational distance’ from higher education and STEM industry may produce bias and misinformation that is harmful to their educational and occupational futures