How does a lambda with empty capture list works?

I have a bit confusion about lambda expression: In C++ primer 5 ed. it is said that :

Classes generated from a lambda expression have a deleted default constructor, deleted assignment operators, and a default destructor. Whether the class has a defaulted deleted copy/move constructor depends in the usual ways on the types of the captured data members (§ 13.1.6, p. 508, and § 13.6.2, p.537).

Now If I try this code:

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>
#include <map>
using namespace std;


int main() 
{

  auto isOdd = [](int x)->bool{ return x % 2;};

  vector<int> vi{10, 8, 5, 6, 7, 24};

  copy_if(vi.cbegin(), vi.cend(), ostream_iterator<int>(cout, ", "), isOdd); // why this works even on C++11?


  auto greater = [](auto x, auto y) { return x > y; };
  std::map<std::string, int, decltype(greater)> map; // this doesn't work?

}

• I don't know how could a lambda with a deleted-default ctor can be defined this way:

  auto pow = [](int x){return x * x;};
  cout << pow(5) << endl; // 25
  

• Why the above works fine even on C++11 although the lambda there has a deleted default-ctor?

• How can you translate this lambda into a class for example equivalent to it?

• But why C++11 complains when passed to map<>?

• So can anyone explain what happens when a lambda doesn't capture anything what the compilr does? What does it generate?