Topological Sector Fluctuations and Curie Law Crossover in Spin Ice

At low temperatures, a spin ice enters a Coulomb phase - a state with algebraic correlations and topologically constrained spin configurations. In Ho2Ti2O7, we have observed experimentally that this process is accompanied by a non-standard temperature evolution of the wave vector dependent magnetic susceptibility, as measured by neutron scattering. Analytical and numerical approaches reveal signatures of a crossover between two Curie laws, one characterizing the high temperature paramagnetic regime, and the other the low temperature topologically constrained regime, which we call the spin liquid Curie law. The theory is shown to be in excellent agreement with neutron scattering experiments. On a more general footing, i) the existence of two Curie laws appears to be a general property of the emergent gauge field for a classical spin liquid, and ii) sheds light on the experimental difficulty of measuring a precise Curie-Weiss temperature in frustrated materials; iii) the mapping between gauge and spin degrees of freedom means that the susceptibility at finite wave vector can be used as a local probe of fluctuations among topological sectors.Comment: 10 pages, 5 figure

The Trichoptera of Panama XIII. Further new country records for caddisflies (Insecta: Trichoptera) from the Republic of Panama

The Republic of Panama currently includes 414 recorded species of Trichoptera. Herein we add two new genera (Hydroptilidae: Angrisanoia Ozdikmen, 2008 and Mayatrichia Mosely, 1937) and 17 new country records (Philopotamidae: Chimarra (C.) tapanti Blahnik, Wormaldia bolivari Muñoz-Quesada and Holzenthal, and Wormaldia zunigae Muñoz-Quesada and Holzenthal; Hydropsychidae: Centromacronema pygmaeum Botosaneanu; Hydroptilidae: Brysopteryx esparta Harris and Holzenthal, Byrsopteryx solisi Harris and Holzenthal, Costatrichia falsa Santos, Takiya, and Nessimian, Mayatrichia illobia Harris and Holzenthal, Metrichia amplitudinis Bueno-Soria and Holzenthal, Ochrotrichia boquillas Moulton and Harris, O. conformalis Bueno-Soria and Holzenthal, O. quinealensis Bueno-Soria and Holzenthal, and O. unica Bueno-Soria and Santiago; Leptoceridae: Triaenodes morai Holzenthal and Andersen; Odontoceridae: Marilia kingsolveri Bueno-Soria and Rojas-Ascencio; and, Helicopsychidae: Helicopsyche alajuela Johanson and Holzenthal and Helicopsyche breviterga Flint) to Panama’s caddisfly fauna. The newly recorded taxa increase Panama’s total known caddisfly fauna to 431 species, distributed among 15 families and 55 genera. These results are part of an ongoing effort to characterize the caddisfly fauna of Panama, and to evaluate the aquatic insect diversity of the country’s major watersheds (cuencas). La República de Panamá actualmente incluye 414 especies registradas de Trichoptera. Aquí agregamos dos nuevos géneros (Hydroptilidae: Angrisanoia Ozdikmen, 2008 y Mayatrichia Mosely, 1937) y 17 nuevos registros para el país (Philopotamidae: Chimarra (C.) tapanti Blahnik, Wormaldia bolivari Muñoz-Quesada y Holzenthal, y Wormaldia zunigae Muñoz-Quesada y Holzenthal; Hydropsychidae: Centromacronema pygmaeum Botosaneanu; Hydroptilidae: Brysopteryx esparta Harris y Holzenthal, Byrsopteryx solisi Harris y Holzenthal, Costatrichia falsa Santos, Takiya, y Nessimian, Mayatrichia illobia Harris y Holzenthal, Metrichia amplitudinis Bueno-Soria y Holzenthal, Ochrotrichia boquillas Moulton y Harris, Ochrotrichia conformalis Bueno-Soria y Holzenthal, Ochrotrichia quinealensis Bueno-Soria y Holzenthal, y Ochrotrichia unica Bueno-Soria y Santiago; Leptoceridae: Triaenodes morai Holzenthal y Andersen; Odontoceridae: Marilia kingsolveri Bueno-Soria y Rojas- Ascencio; y, Helicopsychidae: Helicopsyche alajuela Johanson y Holzenthal y Helicopsyche breviterga Flint) a la fauna de Trichoptera de Panamá. Los taxones recien reportados aumentan el total de la fauna de Trichoptera de Panamá a 431 especies, distribuidas en 15 familias y 55 géneros. Estos resultados son parte de un esfuerzo continuo para caracterizar la fauna de Trichoptera y para evaluar la diversidad de insectos acuáticos de las principales cuencas hidrográficas (cuencas) de Panamá

The Trichoptera of Panama IV. New records for caddisflies (Insecta: Trichoptera) from the Republic of Panama

The Republic of Panama currently has 300 recorded species of Trichoptera distributed among 14 families. Herein we add 42 new country records for Panama, including one new family (Anomalopsychidae) and three new genera (Anomalopsychidae: Contulma; Hydroptilidae: Byrsopteryx and Cerasmatrichia). The newly recorded caddisfly taxa increase Panama’s total known fauna to 342 species, distributed among 15 families and 50 genera. These results are part of an ongoing effort to characterize the caddisfly fauna of Panama, and to evaluate that country’s major watersheds (cuencas)

The Trichoptera of Panama IV. New records for caddisflies (Insecta: Trichoptera) from the Republic of Panama

The Republic of Panama currently has 300 recorded species of Trichoptera distributed among 14 families. Herein we add 42 new country records for Panama, including one new family (Anomalopsychidae) and three new genera (Anomalopsychidae: Contulma; Hydroptilidae: Byrsopteryx and Cerasmatrichia). The newly recorded caddisfly taxa increase Panama’s total known fauna to 342 species, distributed among 15 families and 50 genera. These results are part of an ongoing effort to characterize the caddisfly fauna of Panama, and to evaluate that country’s major watersheds (cuencas)

Long Range Order at Low Temperature in Dipolar Spin Ice

Recently it has been suggested that long range magnetic dipolar interactions are responsible for spin ice behavior in the Ising pyrochlore magnets ${\rm Dy_{2}Ti_{2}O_{7}}$ and ${\rm Ho_{2}Ti_{2}O_{7}}$. We report here numerical results on the low temperature properties of the dipolar spin ice model, obtained via a new loop algorithm which greatly improves the dynamics at low temperature. We recover the previously reported missing entropy in this model, and find a first order transition to a long range ordered phase with zero total magnetization at very low temperature. We discuss the relevance of these results to ${\rm Dy_{2}Ti_{2}O_{7}}$ and ${\rm Ho_{2}Ti_{2}O_{7}}$.Comment: New version of the manuscript. Now contains 3 POSTSCRIPT figures as opposed to 2 figures. Manuscript contains a more detailed discussion of the (i) nature of long-range ordered ground state, (ii) finite-size scaling results of the 1st order transition into the ground state. Order of authors has been changed. Resubmitted to Physical Review Letters Contact: [email protected]

Intra-dance variation among waggle runs and the design of efficient protocols for honey bee dance decoding

Noise is universal in information transfer. In animal communication, this presents a challenge not only for intended signal receivers, but also to biologists studying the system. In honey bees, a forager communicates to nestmates the location of an important resource via the waggle dance. This vibrational signal is composed of repeating units (waggle runs) that are then averaged by nestmates to derive a single vector. Manual dance decoding is a powerful tool for studying bee foraging ecology, although the process is time-consuming: a forager may repeat the waggle run 1- >100 times within a dance. It is impractical to decode all of these to obtain the vector; however, intra-dance waggle runs vary, so it is important to decode enough to obtain a good average. Here we examine the variation among waggle runs made by foraging bees to devise a method of dance decoding. The first and last waggle runs within a dance are significantly more variable than the middle run. There was no trend in variation for the middle waggle runs. We recommend that any four consecutive waggle runs, not including the first and last runs, may be decoded, and we show that this methodology is suitable by demonstrating the goodness-of-fit between the decoded vectors from our subsamples with the vectors from the entire dances

The Trichoptera of Panama VII. Additional new country records for caddisflies from the Republic of Panama

The Republic of Panama currently has 358 recorded species of Trichoptera. Herein we add 25 new country records for Panama. The newly recorded taxa increase Panama’s total known caddisfly fauna to 383 species, distributed among 15 families and 52 genera. These results are part of an ongoing effort to characterize the caddisfly fauna of Panama, and to evaluate that country’s major watersheds (cuencas)

The Trichoptera of Panama VII. Additional new country records for caddisflies from the Republic of Panama

The Republic of Panama currently has 358 recorded species of Trichoptera. Herein we add 25 new country records for Panama. The newly recorded taxa increase Panama’s total known caddisfly fauna to 383 species, distributed among 15 families and 52 genera. These results are part of an ongoing effort to characterize the caddisfly fauna of Panama, and to evaluate that country’s major watersheds (cuencas)