We investigate Andreev reflection in two-dimensional heterojunctions formed by a superconductor in contact with a topological insulator ribbon either possessing or breaking time-reversal symmetry. Both classes of topological insulators exhibit perfect Andreev reflection, which is robust against disorder. This is assigned to topologically protected edge states. In the time-reversal symmetric cas...

Traditionally the charge ratchet effect is considered as a consequence of either the spatial symmetry breaking engineered by asymmetric periodic potentials, or time asymmetry of the driving fields. Here we demonstrate that electrically and magnetically driven quantum dissipative systems with spin-orbit interactions represent an exception from this standard idea. In contrast to the so far well e...

It is well known that unitary symmetries can be “gauged,” i.e., defined to act in a local way, which leads to a corresponding gauge field. Gauging, for example, the charge-conservation symmetry leads to electromagnetic gauge fields. It is an open question whether an analogous process is possible for time reversal which is an antiunitary symmetry. Here, we discuss a route to gauging time-reversa...

In the context of slow quenching dynamics of a p-wave superconducting chain, it has been shown that a Majorana edge state can not be adiabatically transported from one topological phase to the other separated by a quantum critical line. On the other hand, the inclusion of a phase factor in the hopping term, that breaks the effective time reversal invariance, results in an extended gapless regio...

Let m ≥ 2 and k ≥ 2 be integers. We show that K k×m has a decomposition into Hamilton cycles of Kierstead-Katona type if k | m. We also show that K (3) 3×m − T has a decomposition into Hamilton cycles where T is a 1-factor if and only if 3 m and m = 4. We introduce a notion of symmetry and comment on the existence of symmetric Hamilton cycle decompositions of K (k) k×m.

 ‎Let $V$ be an $n$-dimensional complex inner product space‎. ‎Suppose‎ ‎$H$ is a subgroup of the symmetric group of degree $m$‎, ‎and‎ ‎$chi‎ :‎Hrightarrow mathbb{C} $ is an irreducible character (not‎ ‎necessarily linear)‎. ‎Denote by $V_{chi}(H)$ the symmetry class‎ ‎of tensors associated with $H$ and $chi$‎. ‎Let $K(T)in‎ (V_{chi}(H))$ be the operator induced by $Tin‎ ‎text{End}(V)$‎. ‎Th...

We consider the deformed Poincare group describing the space-time symmetry of noncommutative field theory. It is shown how the deformed symmetry is related to the explicit symmetry breaking. PACS number(s): 11.10-z, 11.30Cp

Little Higgs models are an interesting alternative to explain electroweak symmetry breaking without fine-tuning. Supplemented with a discrete symmetry (T-parity) constraints from electroweak precision data are naturally evaded and also a viable dark matter candidate is obtained. T-parity implies the existence of new (mirror) fermions in addition to the heavy gauge bosons of the little Higgs mod...

Little Higgs models offer an interesting approach to weakly coupled electroweak symmetry breaking without fine tuning. The original little Higgs models were plagued by strong constraints from electroweak precision data which required a fine tuning to be reintroduced. An economical solution to this problem is to introduce a discrete symmetry (analogous to R-parity of SUSY) called T-parity. T-par...

This paper deals with the unconventional superconducting properties of Sr2RuO4, the best-known examples of p-wave superconductor with spin-triplet pairing. I shall first review the definition and rough classification of unconventional superconductivity. The formalism for p-wave spin-triplet pairing is examined. This will lead into the discussion of the most likely p-wave state for Sr2RuO4, its ...