Topology of SU(N) gauge theories at T=0 and T=Tc

We calculate the topological charge density of SU(N) lattice gauge fields for values of N up to N=8. Our T=0 topological susceptibility appears to approach a finite non-zero limit at N=infinity that is consistent with earlier extrapolations from smaller values of N. Near the deconfining temperature Tc we are able to investigate separately the confined and deconfined phases, since the transition is quite strongly first order. We find that the topological susceptibility of the confined phase is always very similar to that at T=0. By contrast, in the deconfined phase at larger N there are no topological fluctuations except for rare, isolated and small instantons. This shows that as N->infinity the large-T suppression of large instantons and the large-N suppression of small instantons overlap, even at T=Tc, so as to suppress all topological fluctuations in the deconfined phase. In the confined phase by contrast, the size distribution is much the same at all T, becoming more peaked as N grows, suggesting that D(rho) is proportional to a delta function at N=infinity, centered on rho close to 1/Tc.Comment: 31 page

Topology and Confinement in SU(N) Gauge Theories

The large N limit of SU(N) gauge theories in 3+1 dimensions is investigated on the lattice by extrapolating results obtained for $2 \le N \le 5$. A numerical determination of the masses of the lowest-lying glueball states and of the topological susceptibility in the limit $N\to\infty$ is provided. Ratios of the tensions of stable k-strings over the tension of the fundamental string are investigated in various regimes and the results are compared with expectations based on several scenarios -- in particular MQCD and Casimir scaling. While not conclusive at zero temperature in D=3+1, in the other cases investigated our data seem to favour the latter.Comment: 3 pages, 2 figures; talk presented by B. Lucini at Lattice2001(confinement

The deconfinement transition in SU(N) gauge theories

We investigate the properties of the deconfinement transition in SU(4) and SU(6) gauge theories. We find that it is a `normal' first order transition in both cases, from which we conclude that the transition is first order in the N->infinity limit. Comparing our preliminary estimates of the continuum values of Tc/sqrt(K) with existing values for SU(2) and SU(3) demonstrates a weak dependence on N for all values of N.Comment: 18 page

Properties of the deconfining phase transition in SU(N) gauge theories

We extend our earlier investigation of the finite temperature deconfinement transition in SU(N) gauge theories, with the emphasis on what happens as N->oo. We calculate the latent heat in the continuum limit, and find the expected quadratic in N behaviour at large N. We confirm that the phase transition, which is second order for SU(2) and weakly first order for SU(3), becomes robustly first order for N>3 and strengthens as N increases. As an aside, we explain why the SU(2) specific heat shows no sign of any peak as T is varied across what is supposedly a second order phase transition. We calculate the effective string tension and electric gluon masses at T=Tc confirming the discontinuous nature of the transition for N>2. We explicitly show that the large-N `spatial' string tension does not vary with T for T<Tc and that it is discontinuous at T=Tc. For T>Tc it increases as T-squared to a good approximation, and the k-string tension ratios closely satisfy Casimir Scaling. Within very small errors, we find a single Tc at which all the k-strings deconfine, i.e. a step-by-step breaking of the relevant centre symmetry does not occur. We calculate the interface tension but are unable to distinguish between linear or quadratic in N variations, each of which can lead to a striking but different N=oo deconfinement scenario. We remark on the location of the bulk phase transition, which bounds the range of our large-N calculations on the strong coupling side, and within whose hysteresis some of our larger-N calculations are performed.Comment: 50 pages, 14 figure

Non-perturbative results for large-N gauge theories

It has been known for a long time that large-$N$ methods can give invaluable insights into non-perturbative phenomena such as confinement. Lattice techniques can be used to compute quantities at large $N$. In this contribution, I review some recent large-N lattice results and discuss their implications for our understanding of non-perturbative QCD

Three new host plants of Edessa loxdalii (Hemiptera:Heteroptera:Pentatomidae) and notes on its rearing in the laboratory.

Made available in DSpace on 2017-05-02T23:48:17Z (GMT). No. of bitstreams: 1 ID439262016v99n1p139FloridaEntomologist.pdf: 1259826 bytes, checksum: 731bb667aa3df4c63a3875abaf2e4f20 (MD5) Previous issue date: 2017-02-03201

Comportamento alimentar de percevejos pentatomídeos através do monitoramento eletrônico pelo uso do EPG.

Orientador: Antônio Ricardo Panizzi

Probing behavior of dichelops furcatus (F.) (Heteroptera: Pentatomidae) on wheat plants characterized by electropenetrography (EPG) and histological studies.

Made available in DSpace on 2018-03-15T00:38:01Z (GMT). No. of bitstreams: 1 ID443112017v17n2trab65JInsectSci.pdf: 3172825 bytes, checksum: 380a8aa46018859d0a95311a31a159f2 (MD5) Previous issue date: 2018-03-14bitstream/item/173910/1/ID44311-2017v17n2trab65JInsectSci.pd

Electropenetrographic comparison of feeding behavior of dichelops furcatus (Hemiptera: Heteroptera: Pentatomidae) on soybean and spring cereals .

We used electropenetrography to quantify and compare counts and durations of selected waveforms, produced by adult females of the stink bug Dichelops furcatus (F.). Insects fed on immature soybean pods and immature seed heads of four spring cereals: wheat, black oat, barley, and rye. On all foods, bugs spent over 60% of their plant access time in non-probing activities. This total waveform duration was significantly longer on barley and rye compared to those on soybean and oat; wheat was intermediate. Considering only probing activities, bugs spent longer durations (ca. 2×), on soybean and oat compared to barley, rye, and wheat plants. Bugs produced significantly more pathway events on soybean and rye than on wheat and barley; with a significantly shorter duration per event on rye. The counts and durations of xylem ingestion did not differ among foods. Cell rupturing activities on seeds were longer on soybean (ca. 23%) and oat (ca. 21%), than on barley and rye (ca. 6%). The durations of ingestion events on seeds were significantly shorter on soybean (over 3×) compared to those on barley and wheat; oat and rye were intermediate. However, the ingestion duration per insect did not show significant difference among foods. Results demonstrated that D. furcatus spent more time overall in probing activities on soybean and oat; whereas, rye and barley presented the worst feeding behavior. This study provides important background information for further quantitative studies of stink bugs on different plants, such as development of resistant host plants. Key words: crop plant, feeding behavior, electrical penetration graph, electropenetrograph

Body position of the stink bug Dichelops melacanthus (Dallas) during feeding from stems of maize seedlings.

The Neotropical green-belly stink bug, Dichelops melacanthus (Dallas) is a major pest of maize, Zea mays L. in the main production areas of Brazil. It usually feeds on the stems of young plants (seedlings) causing heavy damage by affecting the plant growth and mitigating seed yield. Laboratory studies were conducted to determine body position (upward or downward) of the bug on plant (seedling) stem during feeding and not feeding activities. Ten visual records were taken per day, each spaced one hour during 30 days of 10 adult bugs of similar age exposed to maize seedlings inside cages (plastic tubes). At each observation, it was recorded if the bug was feeding on the stem (i.e., stylets inserted into the plant tissue) or not, and its body position. During feeding, waveforms were recorded using the EPG (electropenetrography) technique, which were correlated with histological studies to reveal the feeding sites. Results indicated that when they were feeding, the majority of the bugs were in the downward position. In contrast, when the bugs were on the plants, and not feeding, they were mostly in the upward position. Waveforms generated using the EPG coupled with histological studies demonstrated that during ingestion bugs fed from the xylem vessels and from the parenchyma tissue using cell rupture strategy in the latter. No clear explanation was found to explain the preferred downward body position during ingestion, but some hypothesis are speculated. Keywords: Heteroptera, Pentatomidae, feeding behavior, EPG, plant histology. Posição do corpo do percevejo Dichelops melacanthus (Dallas) durante a alimentação em hastes de plântulas de milho O percevejo barriga-verde, Dichelops melacanthus (Dallas) é uma praga importante do milho, Zea mays L. nas principais áreas produtoras do Brasil. Usualmente alimenta-se nas hastes de plantas jovens (plântulas) causando danos severos no seu crescimento e reduzindo o rendimento de grãos. Estudos foram conduzidos em laboratório para determinar a posição do corpo (voltado para cima ou para baixo) dos percevejos nas hastes das plântulas de milho durante as atividades de alimentação e não-alimentação. Foram feitas dez observações por dia, espaçadas por uma hora, durante 30 dias em 10 percevejos adultos com idade semelhante sobre plântulas de milho colocadas em gaiolas (tubos de plástico). Em cada observação, anotou-se se o percevejo estava se alimentando (i.e., estiletes bucais inseridos no tecido vegetal) ou não, e a posição do corpo. Durante a alimentação, ondas eletromagnéticas foram registradas utilizando-se o EPG (técnica da eletropenetrografia), as quais foram correlacionadas com estudos histológicos para revelar os locais de alimentação. Os resultados indicaram que quando os percevejos estavam se alimentando, a maioria estava voltado para baixo. Em contraste, os percevejos sem se alimentar nas plântulas estavam a maioria voltados para cima. As ondas geradas pelo EPG junto com os estudos histológicos revelaram que os percevejos se alimentaram dos vasos do xilema e do tecido parenquimatoso usando a estratégia de ruptura celular no último. Não foi encontrada uma explicação clara para a preferência dos percevejos em se alimentarem na posição voltados para baixo, mas algumas hipóteses são especuladas. Palavras-chave: Heteroptera, Pentatomidae, comportamento alimentar, EPG, histologia da planta