769 research outputs found
D6 Family Symmetry and Cold Dark Matter at LHC
We consider a non-supersymmetric extension of the standard model with a
family symmetry based on D6 Z2 Z2, where one of Z2's is exactly conserved. This
Z2 forbids the tree-level neutrino masses and simultaneously ensures the
stability of cold dark matter candidates. From the assumption that cold dark
matter is fermionic we can single out the D6 singlet right-handed neutrino as
the best cold dark mater candidate. We find that an inert charged Higgs with a
mass between 300 and 750 GeV decays mostly into an electron (or a positron)
with a large missing energy, where the missing energy is carried away by the
cold dark matter candidate. This will be a clean signal at LHC.Comment: 20 pages, 7 figure
A holographic computation of the central charges of d=4, N=2 SCFTs
We use the AdS/CFT correspondence to compute the central charges of the d=4,
N=2 superconformal field theories arising from N D3-branes at singularities in
F-theory. These include the conformal theories with E_n global symmetries. We
compute the central charges a and c related to the conformal anomaly, and also
the central charges k associated to the global symmetry in these theories. All
of these are related to the coefficients of Chern-Simons terms in the dual
string theory on AdS_5. Our computation is exact for all values of N, enabling
several tests of the dualities recently proposed by Argyres and Seiberg for the
E_6 and E_7 theories with N=1.Comment: 16 pages; v4: one reference adde
On the thermodynamic stability and structural transition of clathrate hydrates
Gas mixtures of methane and ethane form structure II clathrate hydrates despite the fact that each of pure methane and pure ethane gases forms the structure I hydrate. Optimization of the interaction potential parameters for methane and ethane is attempted so as to reproduce the dissociation pressures of each simple hydrate containing either methane or ethane alone. An account for the structural transitions between type I and type II hydrates upon changing the mole fraction of the gas mixture is given on the basis of the van der Waals and Platteeuw theory with these optimized potentials. Cage occupancies of the two kinds of hydrates are also calculated as functions of the mole fraction at the dissociation pressure and at a fixed pressure well above the dissociation pressure
Young diagrams and N-soliton solutions of the KP equation
We consider -soliton solutions of the KP equation,
(-4u_t+u_{xxx}+6uu_x)_x+3u_{yy}=0 . An -soliton solution is a solution
which has the same set of line soliton solutions in both
asymptotics and . The -soliton solutions include
all possible resonant interactions among those line solitons. We then classify
those -soliton solutions by defining a pair of -numbers with , which labels line solitons in the solution. The
classification is related to the Schubert decomposition of the Grassmann
manifolds Gr, where the solution of the KP equation is defined as a
torus orbit. Then the interaction pattern of -soliton solution can be
described by the pair of Young diagrams associated with . We also show that -soliton solutions of the KdV equation obtained by
the constraint cannot have resonant interaction.Comment: 22 pages, 5 figures, some minor corrections and added one section on
the KdV N-soliton solution
Argyres-Seiberg duality and the Higgs branch
We demonstrate the agreement between the Higgs branches of two N=2 theories
proposed by Argyres and Seiberg to be S-dual, namely the SU(3) gauge theory
with six quarks, and the SU(2) gauge theory with one pair of quarks coupled to
the superconformal theory with E_6 flavor symmetry. In mathematical terms, we
demonstrate the equivalence between a hyperkaehler quotient of a linear space
and another hyperkaehler quotient involving the minimal nilpotent orbit of E_6,
modulo the identification of the twistor lines.Comment: 27 pages; v2: published versio
Comments on scaling limits of 4d N=2 theories
We revisit the study of the maximally singular point in the Coulomb branch of
4d N=2 SU(N) gauge theory with N_f=2n flavors for N_f= 2, we find
that the low-energy physics is described by two non-trivial superconformal
field theories coupled to a magnetic SU(2) gauge group which is infrared free.
(In the special case n=2, one of these theories is a theory of free
hypermultiplets.) This observation removes a possible counter example to a
conjectured a-theorem.Comment: 13 page
N=2 S-duality via Outer-automorphism Twists
Compactification of 6d N=(2,0) theory of type G on a punctured Riemann
surface has been effectively used to understand S-dualities of 4d N=2 theories.
We can further introduce branch cuts on the Riemann surface across which the
worldvolume fields are transformed by the discrete symmetries associated to
those of the Dynkin diagram of type G. This allows us to generate more
S-dualities, and in particular to reproduce a couple of S-dual pairs found
previously by Argyres and Wittig.Comment: 8 pages, 6 figure
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
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