Spectral Functions in Holographic Renormalization Group Flows

The spectrum of two-point functions in a holographic renormalization group flow from an ultraviolet (UV) to an infrared (IR) conformal fixed point is necessarily continuous. For a toy model, the spectral function does not only show the expected UV and IR behaviours, but other interesting features such as sharp peaks and oscillations in the UV. The spectral functions for the SU(3)xU(1) flow in AdS_4/CFT_3 and the SU(2)xU(1) flow in AdS_5/CFT_4 are calculated numerically. They exhibit a simple cross-over behaviour and reproduce the conformal dimensions of the dual operators in the UV and IR conformal phases.Comment: 20 pages, 6 figures v2: added referene

First Evidence of Persistent Nighttime Temperature Structures in the Neutral Thermosphere of Mars

Using two Mars years of data collected by the Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatiles EvolutioN spacecraft, we reconstruct the local solar time structure of the Martian equatorial thermosphere for the dawn and dusk sectors. The results indicate the presence of several persistent features near the dusk and dawn terminators appearing in the neutral temperature and in the O, Ar, N2, and CO2 densities. The dusk temperature features include a minimum at the terminator surrounded by two local maxima with amplitudes between 20 and 40 K. A nighttime temperature enhancement occurs at a local solar time of 4–5 hr and has an amplitude between 50 and 100 K relative to the surrounding temperatures. The observed enhancements are interpreted to be a result of either nighttime dynamical heating caused by converging and downwelling winds or of a terminator wave originating in the lower atmosphere.Plain Language SummaryNASA’s Mars Atmosphere and Volatiles EvolutioN (MAVEN) spacecraft has been collecting information about the Mars’ upper atmosphere since November 2014. In our study we examined the temperature in the upper atmosphere measured by a gas analyzer on MAVEN that periodically sniffs the air around it. By combining several years of data, we reconstructed a map of atmospheric temperatures dividing it into equatorial daytime, morning, evening, and nighttime regions. The results indicate that local patches of warm atmosphere extend about 300–600 km along the Martian equator (3–6 hr driving distance at highway speeds) on the nightside near morning and evening. One possible reason for these nighttime warm spots is the air currents in the Martian upper atmosphere. As the sun heats the dayside atmosphere, it expands and causes wind currents to blow away from the dayside region. These wind currents can extend away from the equator then return on the nightside colliding in the morning and evening regions. The resulting meeting of wind currents can heat the upper atmosphere. Warmer air escapes from the upper atmosphere faster. Because of this, these nighttime patches of warm air could have contributed to a faster escape of Martian atmospheric gases than previously believed.Key PointsPersistent neutral density and temperature enhancements are observed within 30 min of the dusk terminatorA persistent neutral density enhancement is also observed prior to the dawn terminator at around 4–5 local timeThe neutral density features are observed in all species and appear to be associated with enhancements in neutral temperaturePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146482/1/grl57932.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146482/2/grl57932_am.pd

A Test of the AdS/CFT Correspondence Using High-Spin Operators

In two remarkable recent papers, hep-th/0610248 and hep-th/0610251, the complete planar perturbative expansion was proposed for the universal function of the coupling, f(g), appearing in the dimensions of high-spin operators of the N=4 SYM theory. We study numerically the integral equation derived in hep-th/0610251, which implements a resummation of the perturbative expansion, and find a smooth function that approaches the asymptotic form predicted by string theory. In fact, the two leading terms at strong coupling match with high accuracy the results obtained for the semiclassical folded string spinning in $AdS_5$. This constitutes a remarkable confirmation of the AdS/CFT correspondence for high-spin operators, and equivalently for the cusp anomaly of a Wilson loop. We also make a numerical prediction for the third term in the strong coupling series.Comment: 11 pages, 1 figure; added references, corrected typo

Notes on Supersymmetry Enhancement of ABJM Theory

We study the supersymmetry enhancement of ABJM theory. Starting from a ${\cal N}=2$ supersymmetric Chern-Simons matter theory with gauge group U(2)$\times$U(2) which is a truncated version of the ABJM theory, we find by using the monopole operator that there is additional ${\cal N}=2$ supersymmetry related to the gauge group. We show this additional supersymmetry can combine with ${\cal N}=6$ supersymmetry of the original ABJM theory to an enhanced ${\cal N}=8$ SUSY with gauge group U(2)$\times$U(2) in the case $k=1,2$. We also discuss the supersymmetry enhancement of the ABJM theory with U($N$)$\times$U($N$) gauge group and find a condition which should be satisfied by the monopole operator.Comment: 23 pages, no figure, minor corrections, version to appear in JHE

A Monopole Instanton-Like Effect in the ABJM Model

Making use of ansatzs for the form fields in the 10d type IIA supergravity version of the ABJM model, we come with a solution in the Euclidean signature recognized as a monopole instanton-like object. Indeed we will see that we can have a (anti) self-dual solution at a special limit. While as a topological object, its back-reaction on the original background should be ignorable, we show the energy-momentum tensors vanish exactly. On the field theory side, the best counterpart is an U(1) gauge field of a gauge transformation. To adjust with bulk, the gauge field must prompt to a dynamic one without adding any kinetic term for this dual photon except a marginal, abelian AB-type Chern-Simons term on the boundary. We will see how both side solutions match next to another confirmation from some earlier works of this vortex-particle duality.Comment: 15 pages, minor changes of some formulas, few typos fixed, and a reference adde

Classification of N=6 superconformal theories of ABJM type

Studying the supersymmetry enhancement mechanism of Aharony, Bergman, Jafferis and Maldacena, we find a simple condition on the gauge group generators for the matter fields. We analyze all possible compact Lie groups and their representations. The only allowed gauge groups leading to the manifest N=6 supersymmetry are, up to discrete quotients, SU(n) x U(1), Sp(n) x U(1), SU(n) x SU(n), and SU(n) x SU(m) x U(1) with possibly additional U(1)'s. Matter representations are restricted to be the (bi)fundamentals. As a byproduct we obtain another proof of the complete classification of the three algebras considered by Bagger and Lambert.Comment: 18 page

Vortices, Q-balls and Domain Walls on Dielectric M2-branes

We study BPS solitons in N=6 U(N) \times U(N) Chern-Simons-matter theory deformed by an F-term mass. The F-term mass generically breaks N=6 supersymmetry down to N=2. At vacua, M2-branes are polarized into a fuzzy S^3 forming a spherical M5-brane with topology \mathbf{R}^{1,2} \times S^3. The polarization is interpreted as Myers' dielectric effect caused by an anti-self-dual 4-form flux T_4 in the eleven-dimensional supergravity. Assuming a polarized M2-brane configuration, the model effectively reduces to the well-known abelian Chern-Simons-Higgs model studied in detail by Jackiw-Lee-Weinberg. We find that the potential for the fuzzy S^3 radius agrees with the one calculated from the M5-brane point of view at large N. This effective model admits not only BPS topological vortex and domain wall solutions but also non-topological solitons that keep 1/4 of the manifest N=2 supersymmetry. We also comment on the reduction of our configuration to ten dimensions.Comment: references added, minor modification

On the Strong Coupling Scaling Dimension of High Spin Operators

We give an exact analytic solution of the strong coupling limit of the integral equation which was recently proposed to describe the universal scaling function of high spin operators in N = 4 gauge theory. The solution agrees with the prediction from string theory, confirms the earlier numerical analysis and provides a basis for developing a systematic perturbation theory around strong coupling.Comment: 26 pages, 2 figure

He bulge revealed: He and CO2 diurnal and seasonal variations in the upper atmosphere of Mars as detected by MAVEN NGIMS

Analysis of the Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere Volatiles and EvolutioN (MAVEN) spacecraft closed source data from all orbits with good pointing revealed an enhanced Helium [He] density on the nightside orbits and a depressed He density on the dayside by about a factor of 10–20. He was also found to be larger in the polar regions than in the equatorial regions. The northern polar winter nightside He bulge was approximately twice that of the northern polar summer nightside bulge. The first 6 weeks of the MAVEN prime mission had periapsis at high latitudes on the nightside during northern winter, followed by the midlatitudes on the dayside moving to low latitudes on the nightside returning to the high latitudes during northern summer. In this study we examined the NGIMS data not only in the different latitudes but sorted by solar longitude (Ls) in order to separate the diurnal or local solar time (LST) effects from the seasonal effects. The Mars Global Ionosphere‐Thermosphere Model (M‐GITM) has predicted the formation of a He bulge in the upper atmosphere of Mars on the nightside early morning hours (Ls = 2–5 h) with more He collecting around the poles. Taking a slice at constant altitude across all orbits indicates corresponding variations in He and CO2 with respect to LST and Ls and a diurnal and seasonal dependence.Key PointsData using MAVEN NGIMS for 1 Martian year reveal diurnal and seasonal variations in He and CO2 indicating a changing He bulge in upper atmosphereObserved He bulge is found to agree preliminarily with M‐GITM modeling effortsHe bulge found at Mars is similar to those found at Earth and VenusPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136361/1/jgra53312_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136361/2/jgra53312.pd

Coupling between M2-branes and Form Fields

In the context of low-energy effective theory of multiple M2-branes, we construct the interaction terms between the world-volume fields of M2-branes and the antisymmetric tensor fields of three- and six-forms. By utilizing the compactification procedure, we show coincidence between the dimensionally reduced coupling and the R-R coupling to D-branes in type II string theory. We also discuss that a cubic term proportional to six-form field reproduces the quartic mass-deformation term in the world-volume theory of multiple M2-branes.Comment: 18 page